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Evaluacion de una intervencion con conductores designados para prevenir los accidentes de trafico provocados por el alcohol en las discotecas de Milan, Italia.

INTRODUCCION

El consumo de alcohol es uno de los factores que mas influyen tanto en el riesgo de accidentes de trafico como en la gravedad de sus consecuencias. Segun la Organizacion Mundial de la Salud, en la mayoria de los paises desarrollados en torno al 20% de los accidentes mortales se deben a un conductor que conduce bajo los efectos del alcohol (CBEA). Los choques provocados por el alcohol suelen producirse de noche, generalmente los fines de semana o durante el tiempo libre (1). En Italia el numero y la gravedad de los accidentes de trafico de noche y durante los fines de semana aumenta muchisimo (2). Estos accidentes casi siempre afectan a los jovenes, que son quienes mas frecuentan las discotecas. El proyecto asistencial "PrimaEpoi.it", ejecutado por la Asociacion Ala Milano Onlus, funciona en las discotecas de la ciudad de Milan y contribuye a prevenir los danos derivados del consumo de alcohol y sustancias psicoactivas. En el contexto especifico de las discotecas de Milan se llevo a cabo, como parte del proyecto, un estudio del comportamiento de los conductores que habian consumido alcohol y de sus percepciones. El estudio muestra que la mayoria de los clientes de las discotecas utilizan el coche a la ida y a la vuelta y que el 46% de los conductores presentan una concentracion de alcohol en sangre (CAS) superior al limite legal (0,5 gramos de alcohol por litro de sangre en Italia) (3). Visto esto, se considero util centrar las intervenciones en este grupo con el fin de prevenir los accidentes de trafico provocados por el alcohol. En los ultimos anos la intervencion del conductor designado se ha extendido ampliamente en Italia, pero no se ha publicado ningun estudio de evaluacion. Por ello, los miembros del proyecto Primaepoi.it decidieron disenar, poner en practica y evaluar una intervencion con conductor designado denominada <<Conductor Seguro>>.

Antecedentes

La literatura sobre la evaluacion de este tema abarca unos cuantos estudios publicados entre 1994 y 1999 (4). Hay dos enfoques para fomentar la figura del conductor designado (CD): uno se basa en campanas de concienciacion dirigidas a la poblacion general a traves de los medios, y el otro, similar al proyecto <<Conductor Seguro>>, utiliza programas que ofrecen varios incentivos (bebidas no alcoholicas, comida o entradas gratis) en los establecimientos. En el segundo enfoque se informa al publico de los incentivos a traves de folletos y posters, personal de barra y de puerta de los establecimientos, y anuncios en periodicos y television. Dos efectos positivos de este enfoque son: (i) un descenso del 6,5% en el numero de clientes de bares que reconocieron haber conducido o viajado en compania de un conductor con una CAS >0.5 g/l en las cuatro semanas anteriores (5); y (ii) un creciente numero de personas que se describen como CD6, 7. Segun el Harvard Alcohol Project los beneficios de los programas de conductores designados son que promueven las normas sociales de abstinencia de consumo de alcohol, ofrecen una forma concreta y practica de evitar la CBEA, y fomentan un comportamiento proactivo en el autocontrol de la ingesta de alcohol (8). Ditter et al. observan ciertos aspectos negativos: el numero de conductores que se autodefinen como CD retoman sus costumbres en cuanto se retiran los incentivos, y existen discrepancias entre el CD ideal y la conducta real (4). En un estudio de la CAS media de los CD rondo 0,6 g/l. (9) Por ultimo, aparte de las limitaciones de los datos que ofrecen los propios interesados sobre la frecuencia de CBEA, la pregunta sin respuesta es: ?Como se habrian comportado los CD sin la intervencion? ?Se habrian comportado igual de <<bien>> o habrian utilizado estrategias alternativas para evitar la CBEA?

El proyecto Conductor Seguro

El proyecto <<Conductor Seguro>> pretende prevenir los accidentes de trafico provocados por el alcohol en las discotecas de Milan por medio de intervenciones con conductores designados. El objetivo concreto del proyecto es que disminuya el numero de conductores que salen de las discotecas con una CAS superior al limite legal. La intervencion se ha centrado en los clientes de discotecas que conducen. Se parte de la base de que los conductores con una CAS superior al limite legal tienen mayor riesgo de sufrir accidentes de trafico. La intervencion parte del supuesto de que los incentivos vinculados a la prueba de alcoholemia (<0.5 g/l) al salir de la discoteca disminuyen el porcentaje de conductores con una CAS superior al limite legal. El incentivo es una entrada gratis el mes siguiente. La intervencion fue realizada por profesionales con conocimientos especializados en prevenir la conduccion bajo los efectos del alcohol. Los miembros de la intervencion se dirigieron a grupos de clientes y les pidieron que identificasen al conductor. Una vez identificado, se le informo de la operacion. La participacion fue voluntaria y gratuita. A los conductores que aceptaron se les hizo la prueba de alcoholemia y se les dio una pulsera. Se conto el numero de conductores que se negaron a participar y, cuando fue posible, se hizo constar el motivo de su negativa. Antes de marcharse, los conductores se reunieron con los miembros de la intervencion y cubrieron un cuestionario autoadministrado antes de someterse a la prueba de alcoholemia. Si la CAS del conductor estaba dentro del limite legal, se le regalaba una entrada gratis. En caso contrario, se advertia al conductor que no condujese y se debatian con el estrategias alternativas a la CBEA (p.ej., que condujese un amigo, coger un taxi o un autobus, esperar que disminuyese la CAS, etc.) El personal de campo de la intervencion permanecio en la discoteca hasta que se marcharon todos los clientes.

Objetivo

El presente estudio es una evaluacion de la intervencion <<Conductor Seguro>>. (1) Objetivo 1: verificar la base de la intervencion, que es dar incentivos vinculados a un resultado positivo en la prueba de alcoholemia (<0,5 g/l.) al salir de la discoteca, lo cual redunda en un descenso del porcentaje de conductores que salen de la discoteca con una CAS superior al limite legal. Se espera que los conductores que participen en la operacion <<Conductor Seguro>> tengan una CAS inferior a los que no participen e inferior asimismo al limite legal. Como parte del objetivo, tambien se tendra en cuenta la influencia del genero y la edad de los conductores en la CAS; (2) objetivo 2: identificar el motivo de los conductores para participar en la intervencion y valorar si la operacion ha logrado rebajar la cantidad de alcohol consumido durante la noche; (3) objetivo 3: verificar el supuesto, basado en experiencias previas, de que los conductores que participan en la operacion y aceptan someterse a la prueba de alcoholemia presentan generalmente un perfil de riesgo de CBEA inferior a la poblacion global de clientes de discotecas que vuelven a casa conduciendo.

METODO

El presente estudio se basa en un metodo de investigacion pre-experimental con un grupo de control y sin pre-test (10). Las dos condiciones de la variable independiente fueron la presencia o ausencia de la intervencion del <<Conductor Seguro>>. Para evitar otras variables, solo se incluyeron las discotecas principales de Milan (abiertas al publico general) de una lista de posibles centros de intervencion. Se eligieron cuatro discotecas al azar. El grupo experimental (CD) se formo con los conductores que aceptaron participar en la intervencion y someterse a la prueba de alcoholemia tras cubrir un cuestionario a la salida de la discoteca. Se pidio a los conductores que cubriesen el cuestionario en el momento de salir de la discoteca. El grupo de control (grupo de no-CD) estaba formado por una muestra de conductores que salian de la discoteca una semana despues sin ninguna intervencion. (1) La comparacion de estos dos grupos contemplo la CAS media y el porcentaje de conductores con una CAS >0.5 g/l en el momento de abandonar la discoteca (objetivo 1); (2) para evaluar el impacto de la intervencion (objetivo 2), en el caso del grupo de CD se recogio informacion sobre el numero de conductores que habian reducido su consumo de alcohol tras la intervencion y los motivos para participar en ella; (3) Asimismo, se compararon las pautas de consumo de alcohol del ultimo mes (UM), el numero veces que el cliente se habia emborrachado o habia CBEA (objetivo 3). Para el analisis estadistico se utilizo el programa SPSS (13.0).

Participantes y seleccion

El numero total de conductores abordados fue de 405. La tasa de rechazo fue del 9,1% (n = 37). En el grupo de control (grupo de no-CD) habia 139 conductores, en el grupo experimental (grupo CD) 124, y 105 conductores seleccionados al principio de la noche no se presentaron a la prueba de alcoholemia ni cubrieron el cuestionario al salir de la discoteca. Estos 105 conductores no se incluyeron en ese grupo. El 79,1% (n= 208) de participantes eran hombres y la edad media de 24,6 anos. El rango de edad abarcaba desde 17 hasta 45 anos. No hubo asociaciones significativas en terminos de genero [ji al cuadrado] (d.f. 1) = .004 p>0,5) ni diferencias significativas en terminos de edad (t-test= 1,585 p>0,5) entre los dos grupos. Por tanto, se trataba de grupos homogeneos en lo relativo a estas variables. La mayoria de los participantes eran trabajadores (63,9%; n = 168) o estudiantes (32,7%; n = 86), mientras que el 10,6% (n=28) compaginaban estudios y trabajo, y el 2,7% (n=7) estaban parados. El 19,8% (n=52) de los participantes tenian la ensenanza general basica, el 57,8% (n = 152) el bachillerato, y el 22,1% (n = 58) una carrera universitaria. Como hemos explicado antes, los miembros de la intervencion abordaron aleatoriamente a los clientes a la puerta de la discoteca y les explicaron el programa <<Conductor Seguro>>. En el caso del grupo de no-CD, los encuestadores abordaron a grupos de personas que salian de la discoteca y les explicaron que estaban realizando un estudio sobre los habitos de consumo de alcohol de los clientes de las discotecas. Como incentivo se dio un obsequio a los conductores que aceptaron cubrir el cuestionario y someterse al alcoholimetro. En ambos casos el unico criterio de seleccion fue el de ser conductor. La seleccion se realizo en junio y julio de 2008.

Cuestionario y valoracion de la CAS

Los niveles de CAS de los participantes se midieron con un alcoholimetro portatil profesional SD-400 (Lion Laboratories Ltd, Gran Bretana) que ofrece la CAS (con dos digitos decimales) en gramos de alcohol por litro de sangre. Los grupos de CD y no-CD cubrieron el mismo cuestionario. Se recogio informacion sobre: (i) datos demograficos, (ii) frecuencia de consumo de alcohol el mes anterior (escala ordinal con 5 categorias), si el mes anterior se emborracharon (iii) y con que frencuencia, o (iv) si condujeron alguna vez bajo los efectos del alcohol (y, en caso afirmativo, con que frecuencia). El grupo de CD cubrio una seccion adicional del cuestionario en la que se preguntaba por que participaban en la operacion <<Conductor Seguro>> y si habian modificado su consumo de alcohol a partir de entonces.

RESULTADOS

Objetivo 1

A partir de la CAS de los conductores se realizo un analisis de varianza (ANOVA) 2 genero x 2 tipo de conductor (CD vs. no-CD) con la edad como covariable. Como se ve en la tabla 1, el ANOVA detecto el efecto mas significativo por tipo de conductor, no por genero ni por edad. El resultado del ANOVA no fue significativo en la interaccion genero x conductor. La varianza obtenida por el modelo fue del 13%. La CAS media de los conductores del grupo CD fue mucho mas baja que la del grupo no-CD. Los no CD (CAS media= 0.53 g/l) se embriagaron mas que los CD (CAS media= 0.31 g/l).

Por otro lado, como se ve en la tabla 2, un analisis [ji al cuadrado] demostro que los CD se asociaban de forma significativa con una CAS inferior al limite legal para conducir.

Objetivo 3

Se comparo el grupo CD con el grupo no-CD para comprobar la hipotesis de que los participantes en la operacion presentan un perfil de riesgo de CBEA mas bajo que la poblacion general de clientes de discotecas cuando regresan a casa en coche. Los resultados fueron (Tabla 3): (1) Los no CD declararon beber bastante mas a menudo que los CD; (2) los no CD admitieron al menos un episodio de CBEA mas a menudo que los CD, pero la asociacion no fue significativa; (3) los no CD condujeron bajo los efectos del alcohol con mayor frecuencia que los CD aunque la diferencia no sea estadisticamente significativa; (4) el reconocimiento de al menos un episodio de embriaguez en el mes anterior se asocio significativamente con los no CD; y (5) los no CD se embriagaron con mayor frecuencia que los CD durante el mes anterior. Puesto que los grupos eran homogeneos en terminos de edad y genero, con toda probabilidad estas variables no afectaron al perfil de riesgo de los conductores.

DISCUSION

Los resultados demuestran que, en comparacion con el grupo de control (no-CD), la CAS de los CD fue significativamente mas baja y mas a menudo inferior al limite legal. Timmermann et al. observaron que las mujeres se embriagaban mas que los hombres (9). En este estudio el genero no influyo en la CAS de los conductores y tampoco la edad (objetivo 1). La consideracion de estos datos aislados sugiere que una intervencion con conductores designados modera de forma efectiva el consumo de alcohol de los clientes de las discotecas, reduciendo por consiguiente el riesgo de accidentes del trafico provocados por el alcohol. Sin embargo, otros resultados de esta investigacion indican que semejante razonamiento podria estar sesgado. Los CD y los no-CD se diferencian en ciertos aspectos importantes (objetivo 3). La respuesta positiva a la pregunta sobre un episodio de CBEA en el mes anterior fue similar entre los CD y los no-CD. Sin embargo, los no-CD reconocieron un mayor numero de episodios de CBEA, no significativos estadisticamente. Asimismo, bebieron con menor frecuencia durante el mes anterior y fueron menos propensos a embriagarse al menos una vez el mes anterior. Ademas, los no-CD se embriagaron mucho mas a menudo que los CD. Estos resultados apoyan la idea de que los conductores que participan en la intervencion son bebedores de menor riesgo, aunque no queda claro si tambien se hallan en menor riesgo de caer en CBEA. En contraste con otras intervenciones de reduccion del dano (como los servicios de pasajeros seguros), que atrajeron a los bebedores de riesgo, los participantes en la intervencion del <<Conductor Seguro>> presentan un perfil de riesgo menor que la poblacion general de clientes de las discotecas que regresan a casa en coche (11). Como han advertido Timmermann et al. en esta intervencion se han ofrecido distintos incentivos para valorar la CAS en el grupo de control (grupo de no-CD) con el fin de no disuadir a los que consumian menos alcohol de someterse a la prueba de alcoholemia (9). Esto confirma en cierto modo la idea de que el grupo de no-CD representa a la poblacion esencial de clientes de discotecas de Milan, mientras que el grupo que participo en la intervencion (grupo CD) representa a una subpoblacion expuesta a menor riesgo.

La pregunta de Ditter: <<?Cuantas de estas personas (CD participantes en la intervencion) son nuevos conductores designados elegidos por el programa, frente a los que habrian actuado como tales incluso sin el programa o habrian utilizado otros medios de transporte alternativos y seguros?>>, permanece sin respuesta (4). Suponemos que los CD que participaron en nuestro proyecto seguramente habrian actuado como buenos conductores designados incluso sin intervencion puesto que presentan un perfil de riesgo mas bajo que la poblacion general y afirmaron no haber reducido su consumo habitual de alcohol durante la prueba.

Con respecto al impacto de la intervencion (objetivo 2), la oferta de entradas libres no motivo de forma especial a los clientes de las discotecas para participar en la iniciativa. La razon principal que dieron los CD para participar fue la curiosidad de conocer su CAS. Esto se explica porque a la gente le resulta dificil valorar su propia CAS basandose en el consumo de alcohol de una noche determinada y de su propia percepcion de la sobriedad (3). Por ello les interesa contar con informacion basada en datos empiricos. Otro elemento fundamental fue que la mayoria de los CD afirmaron que la participacion en la iniciativa no habia cambiado en absoluto sus habitos de consumo de alcohol. Esto se explica por el deseo de conocer su propia CAS, mas que por un compromiso con la iniciativa y la atraccion del incentivo de la entrada libre. Teniendo en cuenta la baja proporcion de CD que bebieron menos de los habitual a causa del incentivo (5%, n = 6), parece que dicho incentivo influyo poco en el cambio de habitos de consumo de alcohol de los conductores. Sin embargo, proporciona a los clientes de las discotecas la ocasion de conocer su CAS y puede servir para atraerlos hacia iniciativas de prevencion en ese contexto. El incentivo de la entrada libre no empujo a los conductores a reducir el consumo de alcohol, al menos en el contexto concreto de la ciudad de Milan, donde la entrada suele cobrarse, pero es facil obtener descuentos o entradas libres. En el futuro podria haber programas que explorasen otro tipo de incentivos mas atrayentes.

Hay dos aspectos destacables. En primer lugar, como en otro estudio, la valoracion de la verdadera CAS fue un elemento solido en esta investigacion: constituye un indicador empirico de la verdadera conducta del conductor durante la noche (9). Lamentablemente, los resultados del presente estudio no se pueden comparar con los resultados de la evaluacion de otros programas de conductor designado ensayados previamente, ya que estos ultimos se basaban en la eficacia de la intervencion para incrementar el numero de CD y no tenian en cuenta lo que habian bebido durante la noche (4-7).

En segundo lugar, y de acuerdo con la experiencia del personal de campo, hay que tener en cuenta que las intervenciones con conductores designados no consideran el consumo de sustancias psicoactivas, que tambien afectan negativamente a la capacidad para conducir (12). Aunque un CD no beba, podria conseguir el incentivo sin problemas a pesar de haber consumido drogas durante la noche. En la intervencion <<Conductor Seguro>>, un CD admitio con toda franqueza que habia consumido cannabis, pero no alcohol. Obviamente, es un punto debil de este tipo de intervencion que solo valora el consumo de alcohol.

Este estudio ofrece nuevas perspectivas, pero tiene una serie de importantes limitaciones. En primer lugar, carecemos de informacion sobre los conductores que al entrar en la discoteca aceptaron participar en la intervencion del <<Conductor Seguro>>, pero se marcharon sin cubrir el cuestionario y sin someterse al alcoholimetro (n= 105). Dada la baja tasa de rechazo, parece logico asumir que el grupo de conductores que aceptaron participar era mas representativo del universo objetivo que el subgrupo de conductores que constituian el grupo experimental (grupo CD). Los conductores que no se reunieron con el personal de campo antes de marcharse seguramente presentaban un perfil de riesgo mayor. No sabemos por que no lo hicieron, pero el incentivo de la entrada gratis no fue suficientemente atractivo para ellos. Si hubiesemos entregado el cuestionario a los conductores cuando aceptaron participar en la intervencion, y no antes de salir de la discoteca, tendriamos datos sobre ellos y una vision mucho mas atinada de su perfil de riesgo. Una segunda limitacion, comun en las evaluaciones de los programas con conductores designados, es que los operadores no valoraron lo ocurrido tras salir de la discoteca: si los CD cumplieron realmente su compromiso de llevar al grupo a casa y se abstuvieron de beber el resto de la noche (9). Asimismo, los posibles aspectos negativos del programa de conductores designados no se consideraron en este estudio. Algunas criticas han apuntado que los programas de CD: (1) ofrecen una excusa a los pasajeros para consumir mas alcohol(13); (2) presuponen que beber todo lo que se quiera no resulta problematico mientras no se beba y se conduzca, lo cual contribuye a conductas peligrosas como el consumo compulsivo de alcohol (14); (3) centrarse en los actos de los individuos distrae la atencion de la gente y de los politicos de los factores ambientales y sociales que contribuyen al consumo de alcohol y a la conduccion bajo los efectos del mismo (13,14).

En conclusion, la eficacia de la intervencion del <<Conductor Seguro>> no cuenta con un respaldo contundente. El incentivo de la entrada gratis no invita a los conductores a beber menos, lo cual contrasta con la hipotesis de la intervencion. Por otro lado, la intervencion del <<Conductor Seguro>> atrae a una subpoblacion de bebedores de menor riesgo. Hasta el momento, ningun estudio ha considerado este aspecto. Se necesitan mas investigaciones (i) para evaluar la eficacia de las intervenciones con conductor designado en las que se haya eliminado la parcialidad en la seleccion de conductores, utilizando por ejemplo otros incentivos, y (ii) tener una idea clara del perfil de riesgo de los conductores designados, sobre todo con respecto a la CBEA. Si en el futuro la dinamica de la intervenciones con conductor designado cuenta con el apoyo de pruebas mas claras, podria formar parte de ciertos programas como medida especifica dirigida a un grupo de conductores de menor riesgo, mientras que los servicios de pasajeros seguros pueden orientarse a grupos de bebedores con un alto riesgo de CBEA (11).

INTRODUCTION

The consumption of alcohol is a major factor influencing both the risk of road accidents and the gravity of their consequences. According to the World Health Organization, in the majority of developed countries around 20% of fatal accidents involve at least one driver driving under the influence of alcohol (DUI). Alcohol-related crashes often occur at night and generally at weekends or during free time. (1) In Italy, the number and gravity of car accidents occurring at night and during weekends increases dramatically. (2) Moreover, these accidents frequently involve young people, who are more likely to go clubbing. The outreach project "PrimaEpoi.it", implemented by the association Ala Milano Onlus, works inside clubs in the city of Milan. It aims to prevent damage resulting from the consumption of alcohol and psychoactive substances. Within the specific context of Milan clubs, a survey on drink-driving behavior of drivers and on their perceptions was carried out as part of this project. It shows that the majority of the club-goers use the car to reach and leave the club and that 46% of the drivers present a blood alcohol concentration (BAC) over the legal limit (0.5 grams of alcohol per liter of blood in Italy). (3) It was then considered useful to focus the implementation of interventions on this target group with the aim of preventing alcohol-related road accidents. In past years designated driver intervention has been widely implemented in Italy, but no evaluation study has been published. For this reason the staff of the Primaepoi.it project decided to design, implement and evaluate a designated driver intervention called "Safe Driver".

Background

Literature on the evaluation of this subject comprises a few studies published between 1994 and 1999. (4) There are two approaches used to promote the identification of a designated driver (DD): one is based on awareness campaigns targeting the general population through the media, while the other, similar to the "Safe driver" project, employs programs that offer various incentives (non alcoholic beverages, food or free entrances) in drinking establishments. In the latter approach, the public is informed of the availability of the incentives through flyers and posters, bar tenders and door staff, and newspaper or television advertisements. Two positive effects demonstrated by this approach are: (i) a 6.5% decrease in the number of bar-goers who reported driving, or traveling with a driver, with a BAC >0.5 g/l in the previous four weeks; (5) and (ii) an increasing number of people describing themselves as DDs. (6,7) According to the Harvard Alcohol Project the benefits of the designated driver programs are that they promote the social norm of abstinence from alcohol consumption, offer a specific and practical way to avoid DUI and encourage proactive behavior as regards self-monitoring alcohol intake. (8) Ditter et al. report some possible negative aspects: the number of self-identified DDs seems to return to the baseline immediately after withdrawing the enhanced incentives and often a discrepancy exists between the ideal DD and actual behavior. (4) In a study the mean DDs' BAC was around 0.6 g/l.9 Finally, beyond the limitations of self-report data of the frequency of DUI, the unanswered question is: how would the DDs have behaved without the intervention? Is it possible that these drivers would have behaved as "good" DDs anyway, or might they have used alternative strategies to avoid DUI?

The Safe Driver project

The "Safe Driver" project aims to prevent alcohol-related road accidents in the clubs of Milan by using designated driver interventions. The specific project purpose is to decrease the number of drivers leaving clubs with a BAC above the legal limit. The intervention is aimed at nightclub patrons who drive. The causal assumption is that drivers with a BAC above the legal limit are those who have a higher risk of getting involved in a road accident. The intervention assumption is that offering incentives, linked to a breathalyzer test (<0.5 g/l) when leaving the club, should decrease the percentage of drivers leaving the club with a BAC above the legal limit. The incentive is free entrance to the club for one night during the following month. The intervention was carried out by professional field staff with specific knowledge of drink-driving prevention. The staff intercepted groups of patrons and asked them to identify the driver. Once identified, the driver was informed about the operation. The participation was voluntary and free of charge. The drivers who accepted were breathanalyzed and given a bracelet to wear. The number of drivers who refused to take part was counted and, if possible, the reason of their refusal was recorded. Before leaving, the drivers went back to the staff and completed a self-administered questionnaire before being breathanalayzed. If the driver's BAC was within the legal limit, free entrance was given. If not, the driver was advised not to drive and alternative strategies to DUI were discussed (i.e. letting a friend drive, taking a taxi or a bus, waiting for the BAC to decrease, etc.). The field staff stayed in the club until all the patrons had left.

Objective

The present study is an evaluation of the "Safe Driver" intervention. (1) Objective 1: to verify the intervention assumption, which is that offering incentives, linked to a positive result of the breathalyzer test (<0.5 g/l) when leaving the club, leads to a decrease in the percentage of drivers leaving the club with a BAC above the legal limit. It is expected that drivers participating in the "Safe driver" operation would have lower BAC than those not participating and would have a BAC below the legal limit. As part of this objective, the influence of drivers' gender and age on their BAC will also be considered; (2) objective 2: to understand why drivers take part in the intervention and assess whether the operation was effective in lowering the amount of alcohol drunk during the night; (3) objective 3: to verify the assumption, based on previous experience, that drivers who take part in the operation and accept to be breathalyzed generally present a profile of people with a lower DUI risk than that of the general population of club-goers who drive home.

METHOD

The present study was based on a pre-experimental research method with a control group and no pre-test. (10) The two conditions of the independent variable were the presence or absence of the "Safe Driver" intervention. In order to avoid further variables, only mainstream clubs (for the general public) in the city of Milan were included in a list of possible intervention sites. Four clubs were randomly chosen. The experimental group (DD group) comprised those drivers who accepted to take part in the intervention and to be breathalyzed after completing a questionnaire at the exit of the club. The drivers were asked to complete the questionnaire just before leaving the club. The control group (non-DD group) comprised a sample of drivers leaving the same club a week later without any intervention. (1) The comparison of these two groups concerned the mean BAC and the percentage of drivers with a >0.5 g/l BAC at the time of leaving the club (objective 1); (2) in order to evaluate the impact of the intervention (objective 2), for the DD group only, information was collected regarding the number of drivers who reduced their consumption of alcohol due to the intervention and why they took part in it; (3) the last month (LM) drinking behavior and the number of times patrons got drunk and DUI reports were also compared between the two groups (objective 3). SPSS (13.0) was used for the statistical analysis.

Participants and recruitment

The total number of drivers approached was 405. The refusal rate was 9.1% (N = 37). The control group (non-DD group) comprised 139 drivers, the experimental group (DD group) comprised 124 drivers, and 105 recruited drivers at the beginning of the evening did not come back to be breathalyzed and to complete the questionnaire on leaving the club. Those 105 drivers were not included in that group. 79.1% (N= 208) of participants were male and the mean age was 24.6. Their age range was between 17 and 45. No significant association in terms of gender ([ji al cuadrado] (d.f. 1) = .004 p>0,5) and no significant difference in terms of age (t-test= 1,585 p>0,5) were found between the two groups. So the groups proved to be homogenous in relation to these variables. Most of the participants were workers (63.9%; N = 168) or students (32.7%; N = 86), while 10.6% (N=28) were studying and working at the same time, and finally 2.7% (N=7) were unemployed. 19.8% (N = 52) of participants had a middle school level of education, 57.8% (N = 152) a high school education and 22.1% (N = 58) had a degree. As described above, the staff randomly approached customers entering the club and explained the "Safe driver" event to them. Similarly, for the non-DD group, the staff approached groups of people leaving the club indicating that they were conducting a study on club customers' drinking behavior. As an incentive, a gadget was given to those drivers who agreed to complete a questionnaire and to be breathalysed. In both cases no selection criteria other than being a driver were applied. The recruitment was performed during June and July 2008.

Questionnaire and BAC assessment

Participants' BAC levels were assessed using a professional hand-held SD-400 breathalyzer (Lion Laboratories Ltd, UK) which offers the BAC (two decimal digits) in grams of alcohol per liter of blood. The same questionnaire was completed by DD and non-DD groups. It collected information about: (i) demographic data, (ii) last month drinking frequency (5 step ordinal scale), whether during the previous month they (iii) ever got drunk (and how often) or (iv) ever drove under the influence of alcohol (and, if so, how often). The DD group completed an additional debriefing section in which they were asked why they took part in the "Safe driver" operation and whether they modified their alcohol consumption because of this.

RESULTS

Objective 1

A 2 Gender x 2 Driver type (DD vs. non-DDs) analysis of variance (ANOVA) with age as a covariate was calculated on drivers' BAC. As depicted in table 1, the ANOVA resulted in significant main effect for Driver Type, but not for Gender and age. The ANOVA result was not significant for Gender x Driver type interaction. The variance explained by the model was 13%. The mean drivers' BAC of the DD group was significantly lower than the non-DD group. Non-DDs (Mean BAC= 0.53 g/l) were more intoxicated than DDs (Mean BAC= 0.31 g/l).

In addition, as can be seen in table 2, a [ji al cuadrado] analysis indicated that being a DD was significantly associated with a BAC below the legal driving limit.

Objetivo 2

El 59,7% (n=74) de los CD afirmaron que participaban en la operacion <<Conductor Seguro>> porque les interesaba conocer su CAS. Otras razones fueron: el incentivo de la entrada gratuita (17,7%; n=22), la seguridad de conseguir el incentivo porque pensaban beber poco (16,9%, n=21), la responsabilidad de llevar pasajeros en el coche (12,1%; n = 15), el miedo a las multas y a los accidentes de trafico (12,1%; n = 15), y por ultimo la sensacion de desafio (10,5%; n=13).

La figura 1 describe la modificacion de los habitos de consumo de alcohol de los CD durante la noche. La mayoria de los CD (casi 3 de cada 4) afirmo que habian bebido lo mismo que siempre. De los que bebieron menos (n=28), solo 6 (5% del total de CD) admitieron que la entrada gratis habia sido el motivo principal para participar en el programa. La intervencion tuvo el mismo impacto entre los CD hombres y mujeres. No hubo diferencias entre grupos ya que casi la misma proporcion afirmaron que habian bebido lo mismo que siempre o mas: 74,7% de los hombres (n=208) y 72% (n = 52) de las mujeres ([ji al cuadrado] (g.l.=1) = .79, p>.05). La comparacion por grupo de edad arrojo resultados similares: 66,7% (n = 16) del grupo de los de 20 anos o menos; 77,3% (n = 17) del grupo entre 21 y 23 anos; 74,5% (n=35) del grupo entre 24 y 27 anos; y 71% (n=22) del grupo de mas de 28 anos afirmaron que no habian reducido su consumo de alcohol ([ji al cuadrado] (g.l.=3)= .961, p>.05).

Objective 2

59.7% (N=74) of DDs reported that they took part in the "Safe driver" operation because they were interested in having their BAC assessed. Other reasons were: the free entrance incentive (17.7%; N=22), the fact that they were sure to win the incentive because they expected not to drink much (16.9%, N=21), the responsibility of having passengers to take home (12.1%; N = 15), the fear of getting fines and having car accidents (12.1%; N = 15) and, finally, a sense of challenge (10.5%; N = 13).

Figure 1 describes the modification of DDs' drinking behavior during the night. Most of DDs (almost 3 out of 4) reported that they drank as much as usual. Of those who drank less (N=28), just 6 (5% of total DDs) gave the free entrance incentive as the main reason why they took part in the event. The intervention had the same impact on male and female DDs. There was no difference between groups since nearly the same proportion reported that they drank as much as usual or more: 74.7% of male (N=208) and 72% (N = 52) of female ([ji al cuadrado] (d.f. 1)= .79, p>.05). The comparison by age group led to similar findings: 66.7% (N = 16) of the 20 years-old or less group, 77.3% (N = 17) of 21- to 23-year-old group, 74.5% (N = 35) of 24- to 27-year-old group and 71% (N=22) of the over 28 group reported that they hadn't reduced their alcohol consumption ([ji al cuadrado] (d.f. 3)= .961, p>.05).

Objective 3

The DD group and non-DD group were compared to verify the assumption that those who take part in the operation present a lower DUI risk profile than the general population of club customers who drive home. The results were (see table 3): (1) non-DDs reported that they drank significantly more often than DDs; (2) non-DDs reported at least one DUI episode more often than DDs but the association was not significant; (3) non-DDs drove under the influence of alcohol with a higher frequency than DDs even though the difference was not statistically significant; (4) reporting at least one drunken episode in the previous month was significantly associated with being a non-DD; and (5) non-DDs got drunk significantly more frequently than DDs during the previous month. Since the groups were homogeneous in terms of age and gender, these variables most likely did not affect drivers' risk profile.

DISCUSSION

Findings showed that compared with the control group (non-DDs), the mean BAC of DDs was significantly lower and more often below the legal limit. Timmermann et al. found that women were more intoxicated than men.9 In this study gender, and also age, had no influence on drivers' BAC (objective 1). This data, if considered alone, suggests that a designated driver intervention effectively motivates club customers to moderate their consumption of alcohol, thus reducing the risk of alcohol-related road accidents. However, other results of this research suggest that this reasoning may be biased. DDs and non-DDs seem to differ in some important aspects (objective 3). The positive response to the question of having a DUI episode at least once in the last month were similar for DDs non-DDs. However non-DDs reported a higher number of DUI episodes: although not statistically significant. They also drank less often during the preceding month and also are less likely to have been drunk at least once during the preceding month. Moreover, non-DDs got drunk significantly more often than DDs. These results provide some support to the suggestion that drivers who take part in the intervention are less risk drinkers even though it is not clear if they are also at less risk for DUI. In contrast with other harm reduction interventions (such as safe riders services) that proved to attract at-risk drinkers, people who take part in the "Safe driver" intervention seem to present a lower risk profile than the general population of club customers who drive home. (11) As Timmermann et al. advised, in this intervention different incentives to the BAC assessment have been offered for the control group (non-DD group) in order to reduce the risk of dissuading those who consumed less alcohol from being breathalyzed. (9) This gives some support to the notion that non-DD group may indeed be representative of the target population of club customers in Milan, while the group that took part in the intervention (DD group) represents a sub-population exposed to a lower risk.

Anyway, Ditter's question "how many of these people (DDs participating in the intervention) are new designated drivers recruited by the program, as opposed to those who would have acted as such even without the program, or would have used other safe transportation alternatives?" remained unanswered. (4) We speculate that the DDs that took part in our project may already act as a good designated driver even without the intervention, since they have a lower risk profile than the general population and since they reported that they did not reduce their alcohol consumption during the event.

In respect of the impact of the intervention (objective 2), the offer of free entrance does not seem to have succeeded in motivating the club-goers who drive to take part in the initiative. The main reason why DDs took part was their curiosity to assess their BAC. An explanation for this may be that people find it difficult to estimate their own BAC on the basis of their alcohol consumption in a given night and their self-perception of sobriety. (3) For this reason they might be interested in obtaining feedback from empirical data. Another critical element was that most DDs reported that participation in the initiative didn't change their drinking behavior at all. This may be explained by the prevailing desire to know one's BAC, rather than a commitment to the initiative and an interest in the free entrance incentive. Given the low proportion of DDs that drank less than usual because of the incentive (5%, N = 6), it seems that this incentive has a poor impact on the change in drivers' drinking behavior. It does, however, provide an opportunity for club clients to have their BAC assessed and it may be a good way to involve them in prevention initiatives in this context. The incentive of free entrance does not seem to motivate the drivers to drink less, at least in the specific context of the city of Milan, where admission is often charged, but where it is not difficult to obtain discount rates or free entrance. Future programs might explore other types of incentives that may prove to be more attractive.

Two aspects are noteworthy. First, as in another study, the assessment of actual BAC was a solid element in this study: it represents an empirical indicator of the driver's actual behavior during the night. (9) Unfortunately, the findings of the present study are not comparable with the results of the evaluation of other designated driver programs previously illustrated, as those results were based on the effectiveness of the intervention to increase the number of DDs and didn't consider how much they had drunk during the night. (4-7)

Second, from the field staff's experience, it should be noted that designated driver interventions do not consider at all the use of psychoactive substances, which also may have negative effects on the driver's capacity. (12) If a DD doesn't drink, s/he could easily get the incentive even if s/he used drugs during the night. In the "Safe driver" intervention, a DD frankly admitted the use of cannabis but not of alcohol. Obviously this is a critical aspect of this kind of intervention because only alcohol consumption is assessed.

While this study provides new insights, some limitations are noteworthy. First, we have no information about drivers who entered the club agreeing to take part in the "Safe driver" intervention, but leaving the club without completing the questionnaire and without being breathalysed (N= 105). Given the low refusal rate, it seems reasonable to assume that the overall set of drivers agreeing to take part was more representative of the target population than the subset of drivers constituting the experimental group (DD group). The drivers who did not come back to the field staff before leaving probably had a greater risk profile. We do not know why they did not return, but possibly the free entrance incentive was not attractive enough for them. If we had given the questionnaire to drivers when they agreed to take part in the intervention and not just before they left the club, we could have collected data on those drivers. That would have given much more insight into those drivers' risk profile. A second limitation, common in designated driver program evaluations, is that the operators did not assess what happened after the club, whether the DDs actually followed through on their commitment by driving the group home and by refraining from drinking and driving for the rest of the evening. (9) Also, the possible negative aspects of the designated driver approach were not considered in this study. Some critics have speculated that DD programs: (1) give an excuse to DDs' passengers to consume more alcohol; (13) (2) imply that it is not problematic to drink as much as you want as long as you do not drink and drive, contributing to dangerous behavior like binge-drinking; 14 (3) focusing on the actions of individuals may divert the public's and policymakers' attention from addressing the environmental and social factors that contribute to both alcohol consumption and drink-driving. (13,14)

In conclusion, the effectiveness of the "safe driver" intervention does not seem to be supported by strong evidence. The incentive of free entrance does not motivate drivers to drink less. This is in contrast with the intervention's assumption. Moreover, the "Safe driver" intervention seems to reach a subpopulation of drinkers who are less at risk. So far, no research studies have taken this fact into consideration. More research is needed (i) to evaluate the effectiveness of designated driver interventions where the bias in the selection of drivers has been removed, by, for example, using other incentives and (ii) to have a clear understanding of designated drivers' risk profile, especially as regards DUI. If in the future the dynamics of designated driver interventions is supported by clearer evidence, they might be part of programs as specific measures for a target of less risky drivers, while safe ride services may be used instead for a target of drinkers at high risk for DUI. (11)

recibido: diciembre 2008

aceptado:junio 2009

REFERENCIAS /REFERENCES

(1.) World Health Organization. Drinking and driving: a road safety manual for decision-makers and practitioners. Global Road Safety Partnership 2007.

(2.) ISTAT Istituto Nazionale di Statistica (IT). [Data on traffic accidents in Italy during the year 2006]. 2007. Italian.

(3.) Fornari L. Drink-driving and perceptions: a field survey in the recreational settings of Milano, Italy. Project UMG. Communication presented at Club Health 2008 conference. Ibiza, Spain, 23rd-25th June 2008.

(4.) Ditter SM, Elder RW, Shults RA, Sleet DA, Compton R, Nichols JL. Effectiveness of designated driver programs for reducing alcohol-impaired driving. A Systematic Review. Am J Prev Med 2005; 28: 281-87.

(5.) Boots K. The designated driver program: an outcome evaluation. Health Promot J Austr 1994; 4: 26-9.

(6.) Brigham T, Meier S, Goodner V. Increasing designated driving with a program of prompts and incentives. J Appl Behav Anal 1995; 28: 83-94.

(7.) Meier S, Brigham T, Gilbert B. Analyzing methods for increasing designated driving. J Prev Intervention Community 1998; 17: 1-14.

(8.) Winsten J. Promoting designated drivers: the Harvard Alcohol Project. Am J Prev Med 1994; 10: 11-4.

(9.) Timmerman M, Geller E, Glindemann K, Fournier A. Do the designated drivers of college students stay sober? J Safety Res 2003; 34: 127-33.

(10.) Campbell DT, Stanley JC. Experimental and quasi-experimental designs for research. Chicago: Rand McNally; 1963.

(11.) Caudill BD, Harding WM, Moore BA. At-risk drivers use safe ride services to avoid drinking and driving. J Subst Abuse 2000; 11: 149-59.

(12.) Kelly E, Darke S, Ross J. A review of drug use and driving: epidemiology, impairment, risk factors and risk perceptions. Drug Alcohol Rev 2004; 23:319-44.

(13.) Aspler R, Hardin W, Goldfein J. The review and assessment of designated driver programs as an alcohol countermeasure approach, Washington DC: U.S. Department of Transportation, National Highway Traffic Safety Administration 1987.

(14.) DeJong W, Wallack L. The role of designated driver programs in the prevention of alcohol-impaired driving: a critical reassessment. Health Educ Q 1992; 19: 429-42.

Giovanni Aresi; Luca Fornari; Chiara Repetto; Marta Scolari

Asociacion Ala Milano Onlus - Primaepoi.it project Enviar correspondencia a:

Giovanni Aresi, via Boifava 60/a 20142 Milano, Italia. E-mail: g.aresi@alainrete.org
Tabla 1. ANOVA de Concentracion de Alcohol en Sangre (CAS).

Table 1: ANOVA for BAC.

Fuente / Source       g.l. / df   MS      F       Significacion
                                                   Significance

Edad / Age            1           .209    .893        p=.346
Genero / Gender       1           .751    3.202       p=.75
Tipo de conductor /   1           2.301   9.840       p<.05
Driver type
Genero x tipo de      1           .15     .64         p=.800
conductor / Gender
XDrivertype
Error / Error         252         .235

Tabla 2. Concentracion de alcohol en sangre (CAS) de
conductores por encima del limite legal.
Comparacion entre el grupo CD y el no CD.

Table 2: Drivers' BAC above legal limit
comparison between DD and non-DD groups.

Variable                          Grupo CD /     Grupo no-CD /
                                    DD group      Non-DD group

CAS de conductores /   Si / Yes   22,8% (N=28)     46% (N=63)
Drivers' BAC
Por encima del         No / No    77,2% (N=95)    54% (N= 74)
limite legal
de 0,5g/l / above
legal limit 0,5g/l

Variable               Analisis /    Significacion /
                        Analysis       Significance

CAS de conductores /   %2 (g.l.=1)
Drivers' BAC
Por encima del           15.362           p<.001
limite legal
de 0,5g/l / above
legal limit 0,5g/l

Tabla 3: Comparacion entre los grupos de CD y no-CD para determinar
un perfil de riesgo.

Table 3: Comparison between DD and non-DD groups to determine a
risk profile.

Variable                                      Grupo CD /
                                              DD group

                            Nunca / Never     10,5% (n=13)
                            1 vez o menos /   9,7% (n=12)
                            Once or less
(l) Frecuencia consumo      2-3/mes /         37,9% (n=47)
alcohol, ultimo mes /       2-3 a month
(1) LM drinking frequency   1-3/semana /      29% (n=36)
                            1-3 a week
                            4 o mas /         12,9% (n=16)
                            4 or more

(2) CBEA al menos 1 vez,    Si / Yes          29% (n=36)
ultimo mes /
(2) LM DUI at least once    No / No           71% (n=88)
(3) Numero de CBEA UM /                       0,65
(3) LM number of DUI        Promedio / Mean   (d.t.=0,116)

(4) Embriaguez al menos 1   Si / Yes          33,9% (n=42)
vez , ultimo mes /
(4) LM drunkenness at       No / No           66,1% (n=82)
least once
(5) Frecuencia de           Promedio / Mean   0,81
embriaguez UM /
(5) LM frequency of                           (d.t.=1.424)
drunkeness

Variable                                      Grupo no-CD /
                                              Non-DD group

                            Nunca / Never     2,2% (n=3)
                            1 vez o menos /   10,1% (n=14)
                            Once or less
(l) Frecuencia consumo      2-3/mes /         14,5% (n=20)
alcohol, ultimo mes /       2-3 a month
(1) LM drinking frequency   1-3/semana /      42% (n=58)
                            1-3 a week
                            4 o mas /         31,2% (n=53)
                            4 or more

(2) CBEA al menos 1 vez,    Si / Yes          37,6% (n=50)
ultimo mes /
(2) LM DUI at least once    No / No           62,3% (n=83)
(3) Numero de CBEA UM /                       0.98
(3) LM number of DUI        Promedio / Mean   (d.t.=0,146)

(4) Embriaguez al menos 1   Si / Yes          52,2% (n=70)
vez, ultimo mes /
(4) LM drunkenness at       No / No           47,8% (n=64)
least once
(5) Frecuencia de           Promedio / Mean   1,69
embriaguez UM /
(5) LM frequency of                           (s.d=2.532)
drunkeness

Variable                                      Analisis /
                                              Analysis

                            Nunca / Never
                            1 vez o menos /   U de Mann-Whitney
                            Once or less
(l) Frecuencia consumo      2-3/mes /
alcohol, ultimo mes /       2-3 a month
(1) LM drinking frequency   1-3/semana /      5684.5
                            1-3 a week
                            4 o mas /
                            4 or more

(2) CBEA al menos 1 vez,    Si / Yes          [chi square (g.l.=1)
ultimo mes /
(2) LM DUI at least once    No / No           2,113
(3) Numero de CBEA UM /                       t-test
(3) LM number of DUI        Promedio / Mean   -1.812

(4) Embriaguez al menos 1   Si / Yes          %2 (g. i .=1)
vez, ultimo mes /
(4) LM drunkenness at       No / No           8.845
least once
(5) Frecuencia de           Promedio / Mean   t-test
embriaguez UM /
(5) LM frequency of                           -3.442
drunkeness

Variable                                      Significacion /
                                              Significance

                            Nunca / Never
                            1 vez o menos /
                            Once or less
(l) Frecuencia consumo      2-3/mes /
alcohol, ultimo mes /       2-3 a month
(1) LM drinking frequency   1-3/semana /      p<.001
                            1-3 a week
                            4 o mas /
                            4 or more

(2) CBEA al menos 1 vez,    Si / Yes          No significativa /
ultimo mes /
(2) LM DUI at least once    No / No           Not significant
(3) Numero de CBEA UM /                       No significativo /
(3) LM number of DUI        Promedio / Mean   Not significant

(4) Embriaguez al menos 1   Si / Yes
vez, ultimo mes /
(4) LM drunkenness at       No / No           p<.05
least once
(5) Frecuencia de           Promedio / Mean   p=.001
embriaguez UM /
(5) LM frequency of
drunkeness

LM = last month

DVI= driving under the influence

Figura 1: Consumo de alcohol de los CD /

Figure 1: DDs drinking behavior

?Ha modificado su consumo de alcohol
despues de participar en el proyecto?

"Did you modfy your consumption as a
result of taking part in this event?

Yes. I drank only at the
beginning of the evening
4
3,2%

Si, bebi solo
al principio de la noche
4
3,2%

Si, bebi mai
2
1,6%

Yes. I drank
more 2
1,6%

Yes. I drank less
28
22,6%

Si, bebimos
28
22,6%

No, bebi lo misn
de siempre
90
72,6%

No. I drank the ame
amount as usual
90
72,6%
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Author:Aresi, Giovanni; Fornari, Luca; Repetto, Chiara; Scolari, Marta
Publication:Adicciones
Date:Dec 1, 2009
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