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Alcohol and mortality: is there a U-shaped relation in elderly people?

Abstract

Objective: to assess the relation between alcohol intake and mortality among seven cohorts of middle-aged and elderly Danes.

Design: prospective population study with baseline assessment of alcohol- and tobacco consumption, educational level and body mass index, and a mean of 11.5 years follow-up of mortality.

Subjects: 16 304 men and women aged 50 years or more.

Main outcome measure: number and time of deaths from 1974 to 1995 as ascertained by the national central person register.

Results: the effect of alcohol intake on mortality did not differ between middle-aged (50-64 years, mean = 56.6 years) and elderly subjects ([is greater than] 64 years old, mean = 69.9 years). There was a U-shaped risk function in both age groups, which persisted also when adjusting for age, sex, smoking habits, level of education and body mass index. Abstaining women had a relative risk of 1.29 (95% confidence limits 1.17-1.42) as compared with light drinkers (1-6 drinks per week), while the relative risk for abstaining men was 1.22 (95% confidence limits; 1.08 to 1.37) as compared with light drinkers. Heavy drinking women ([is greater than] 28 drinks per week) had a relative risk of 1.23 (95% confidence limits; 0.85 to 1.78) and heavy drinking men (more than 69 drinks per week) had a relative risk of 2.11 (95% confidence limits 1.66-2.69), both compared with light drinkers.

Conclusion: among the middle-aged and elderly women and men, a light alcohol intake is associated with lower mortality than abstention or heavy drinking.

Keywords: alcohol, elderly people, mortality

Introduction

In several large population studies abstainers and heavy drinkers have shown a higher mortality than moderate drinkers [1-5]. The deleterious effects of heavy drinking on morbidity and mortality from, for example, liver cirrhosis, several cancers, suicides, traffic accidents and work-related injuries are well described [6-8]. At the lower end of the consumption scale, it has been suggested that abstainers are at a higher risk of mortality from cardiovascular disease [9-10].

In a previously reported cohort study from Copenhagen we found no statistical interaction between age and the effect of alcohol on mortality [2]. A recent large American study found that the beneficial effect of a light alcohol intake was greater among older than among younger women [3]. Here, women at high risk of cardiovascular disease (due to risk factors such as old age, diabetes mellitus, family history of coronary heart disease, high cholesterol and hypertension) were found to experience an additional effect of a light alcohol intake with regard to all-cause mortality [3]. Since the relation between alcohol intake and mortality among elderly people has been only sparsely studied [11-14], the aim of the present study was to analyse the effect of alcohol on mortality among middle-aged and elderly men and women.

Population and methods

The Copenhagen Centre for Prospective Population Studies comprises three Danish prospective population studies: the Copenhagen City Heart study, the Copenhagen Male study and the Glostrup Population study--which also comprises the Monitoring of Trends and Determinants in Cardiovascular Diseases (MONICA) studies [15-17]. Characteristics of the different population studies are shown in Table 1. A total of 6905 women and 9629 men aged 50 years or more were included in the study. Subjects above age 50 were only excluded if there were missing data (n = 93) or if they had participated in more than one study (n = 137), in which case they were excluded from the cohort to which they contributed the shortest observation time.

Table 1. Characteristics of the over-50-year-old participants from the Copenhagen Centre for Prospective Population Studies, according to sub-population
                                        Age (years)

Study                         Year(s)   Mean   Maximum

Copenhagen City Heart study   1976-78   60     93
Copenhagen Male study         1985-86   62     75
Glostrup Population study     1977      80     80
 1897
Glostrup Population study     1974      70     70
 1914
MONICA I                      1982      55     60
MONICA II                     1987      55     60
MONICA III                    1991      60     70
Total                         -         -      -

                              No. (and %) of subjects, by sex and
                                               age

                              Men                  Women

Study                         Subjects   Deaths   Subjects   Deaths

Copenhagen City Heart study   3998       2310     4607       1708
Copenhagen Male study         2588        555        0          0
Glostrup Population study       89         89      126        123
 1897
Glostrup Population study      375        195      344        115
 1914
MONICA I                       922        192      839        101
MONICA II                      369         43      353         20
MONICA III                     580         47      559         26
Total                         9476       3431     6828       2093

                                             Follow-up time
                                             (years)
                              Observation
Study                         time (years)   Mean    Maximum

Copenhagen City Heart study   120 686        14.2    18.9
Copenhagen Male study          26 383         8.4    10.0
Glostrup Population study        1660         7.4    18.4
 1897
Glostrup Population study        6472         8.9    11.6
 1914
MONICA I                       20 560        11.7    13.1
MONICA II                        6231         8.6     9.3
MONICA III                       4793         4.2     4.8
Total                         186 785        11.5    -


MONICA, Monitoring of Trends and Determinants in Cardiovascular Diseases.

In all three population studies the subjects completed a self-administered questionnaire concerning health-related issues including drinking and smoking habits, as well as duration of school education, and the answers were checked by the staff during the examination.

Alcohol intake

All participants were asked in multiple-choice format about the average number of drinks consumed per week. One beverage contains between 9-13g of alcohol. The subjects were classified according to the total weekly alcohol intake of [is less than] 1, 1-6, 7-13, 14-27, 28-41, 42-69 or [is greater than or equal to] 70 beverages per week.

Smoking habits

The subjects reported if they were never-smokers, ex-smokers or current smokers. Current smokers were categorized according to the amount of tobacco smoked per day. For the analysis, five groups were defined: never-smokers, ex-smokers and smokers of 1-14g, 15-24g or [is greater than] 25g per day.

School education

The subjects were asked to categorize themselves according to duration of school education ([is less than] 8 years, 8-10 years or [is greater than] 10 years).

Body mass index

The participants had their height and weight in light clothes measured. Body mass index was calculated as weight divided by height squared (kg/[m.sup.2]).

The survival status of the population samples was followed until 9 January 1995, using the unique person identification number in the national central person register. The observation time for each participant was the period from the initial examination until 9 January 1995 or until death, disappearance or emigration during the observation period. The mean follow-up time for each cohort is shown in Table 1. The total observation time was 186 785 years.

Statistical analysis

The data were analysed by means of Cox regression analysis in SPSS Win 6.1.

The first series of models included age, gender, and alcohol intake. A second series of models included age, gender, alcohol intake and either body mass index, school education or smoking. The final model included all six factors.

Finally, the mortality rate ratios were estimated, after stratification on the two age groups: middle-aged (50-64 years) and elderly (older than 64 years).

Results

In all the cohorts of The Copenhagen Centre for Prospective Population Studies men reported drinking more than women. Apart from a lower average intake among elderly compared with the middle-aged subjects, alcohol intake among men and women had a similar pattern of distribution in the two age groups. In the whole population under study, 40.5% of the women and 12.0% of the men were abstainers (defined as having an alcohol intake of [is less than] 1 drink per week). Only a small fraction (0.5%) of the women, but 7.0% of the men, had an intake of [is greater than] 41 drinks per week (Table 2). Among the elderly population there was a larger fraction of abstaining women (52.5%) and of abstaining men (15.9%) than in the sample as a whole.
Table 2. Alcohol consumption by sex, age and outcome

                    No. (and %) of subjects, by sex and age
                    Men
                    50-64 years              >64 years
Alcohol intake
(drinks per week)   Subjects   Deaths        Subjects   Deaths
<1                   686        222 (32.4)    447        252 (56.4)
1-6                 1359        373 (26.7)    586        337 (57.5)
7-13                1424        385 (27.0)    615        345 (56.1)
14-27               1910        438 (22.9)    792        405 (51.1)
28-41                756        256 (33.9)    228        117 (51.3)
42-69                416        161 (38.7)    118         64 (54.2)
>69                  110         62 (56.4)     17         14 (82.4)
Total               6661       1897 (28.5)   2803       1534 (54.7)

                    Women
                    50-64 years              >64 years
Alcohol intake
(drinks per week)   Subjects   Deaths        Subjects   Deaths
<1                  1841        464 (25.2)    921       539 (58.5)
1-6                 2108        434 (20.7)    535       252 (47.1)
7-13                 669        130 (19.4)    197       112 (56.9)
14-27                382         84 (22.0)     90        48 (53.3)
28-41                 59         17 (28.8)      6         5 (83.3)
42-69                 22          8 (36.4)      4         0 (0)
>69                    6          0 (0)         0         0 (0)
Total               5087       1137 (22.4)   1753       956 (54.5)


Of the 16 504 subjects aged 50 years or more, 5524 died during follow-up. Separate analyses revealed U-shaped relations between alcohol intake and mortality in all the cohorts. In the pooled analysis, abstainers ([is less than] 1 drink per week) had an increased mortality risk of 1.27 (95% confidence limits 1.17-1.37), compared with those who drank 1-6 drinks per week. The risk function increased steadily from 1.00 among light drinkers to reach 1.91 (95% confidence limits 1.51-2.42) among those who drank [is greater than] 69 drinks per week (Figure 1).

[Figure 1 ILLUSTRATION OMITTED]

The population was divided into middle-aged and elderly, and we found identical U-shaped risk functions in the two groups (Figure 1). Middle-aged abstainers had an increased risk of 1.28 (95% confidence limits 1.15-1.42) and elderly abstainers had an increased risk of 1.25 (95% confidence limits 1.12-1.40) compared with light drinkers.

No interaction between alcohol intake and gender was found. This was confirmed by an analysis of the data stratified on gender, in which two U-shaped risk functions appeared (data not shown). Thus, abstaining women had an increased risk of 1.29 (95% confidence limits 1.17-1.43) compared with light drinkers, while the risk was 1.22 (95% confidence limits 1.08-1.38) among men. Both women and men with a high alcohol intake had an increased risk of dying. Women who drank [is greater than or equal to] 28 drinks per week had an increased risk of 1.23 (95% confidence limits 0.85-1.78) compared with light drinkers. Men who drank [is greater than] 69 drinks per week had a risk of 2.11 (95% confidence limits 1.66-2.69).

The above mentioned analyses were all controlled for the chosen co-variates. Adjustment for age, sex, body mass index, level of education and smoking habits did not significantly alter the estimates.

Discussion

We found a uniform pattern of U-shaped curves for alcohol intake and mortality in both middle-aged and elderly subjects.

Many clinical and epidemiological studies have found evidence supporting that light to moderate alcohol intake, perhaps by various intermediate factors, reduces the risk of cardiovascular disease [18, 19]. Mean serum high-density lipoprotein concentration is higher among light drinkers than among abstainers, [20, 21] and alcohol has been shown to decrease platelet aggregation [22-24].

The relation between alcohol intake and all-cause mortality has been assessed in numerous prospective population studies from different countries. The incidence of various causes of deaths differs from age group to age group. Thus, in women, the proportion of deaths that are due to breast cancer decreases after middle-age while the relative frequency of death from cardiovascular disease increases. The question of a specific effect-modification by age has only sparsely been addressed. Fuchs et al. [3] found that the beneficial effect of a light alcohol intake was higher among elderly than among younger women.

The Copenhagen Centre for Prospective Population Studies comprises cohorts examined at different points in time. This means that the subjects have been questioned about their alcohol intake over a period during which both the availability and acceptability of alcohol in Denmark has changed. It further implies large differences in mean observation time cohort to cohort (Table 1). Our finding that the U-shaped relation between alcohol intake and mortality remained among elderly people of different time periods, indicates that the risk function is stable and independent of these factors.

Our findings are consistent with those of Scherr et al., who described a U-shaped relation between alcohol and mortality among subjects aged 65 or older [11]. The descending leg of the U-shaped risk function has been attributed to higher mortality from coronary heart disease among abstainers than among moderate drinkers. In a small cohort, Colditz et al. found that there was a beneficial effect on risk of coronary heart disease from a light alcohol intake in elderly people [13].

The U-shaped relation between alcohol and mortality persists in old age, and may have public health implications. Firstly, the motivation for drinking rather than not drinking may differ between younger and elderly people. Secondly, the risk of inducing addiction in a population of older people may be smaller. On the other hand, one should not exaggerate the benefits of an increase in alcohol intake amongst elderly subjects, particularly those who abstain. Falls are more frequent among those who drink alcohol than among those who do not [25].

Our results may be a consequence of previous alcohol habits over a longer period of time, and do not imply that it is advisable to encourage elderly people to drink moderately. This type of evidence would require measurements of the alcohol habits at more than one point in time.

In conclusion, a light to moderate alcohol intake in older as well as middle aged people is predictive of a reduction in mortality from all causes compared with those who abstain or drink heavily.

Key points

* The relationship between alcohol intake and all-cause mortality has been shown to be U- or J-shaped.

* In a pooled analysis from several large cohorts from Copenhagen, a uniform pattern of U-shaped relations between alcohol intake and all-cause mortality was found among middle-aged and elderly men and women.

Acknowledgement

The Copenhagen Centre for Prospective Population Studies (steering group: T. I. A. Sorensen, K. Borch-Johnsen, P. Schnohr, H. O. Hein and N. Keiding) comprises the Copenhagen Male study (H. O. Hein, F Gyntelberg and P. Suadicani), the Glostrup Population studies (T. Jorgensen, H. Ibsen, K. Borch-Johnsen, P. Thorvaldsen and J. Clausen) and the Copenhagen City Heart study (G. Jensen, E Schnohr, J. Nyboe, M. Appleyard, P. Lange, M. Gronbaek and B. Nordestgaard).

We thank Merete von Holstein for secretary assistance. This study was financially supported by the Danish National Board of Health and the Danish Heart Foundation.

References

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Received 21 August 1997; accepted 31 October 1997

MORTEN GRONBAEK, ALLAN DEIS(1), ULRIK BECKER(2), HANS OLE HEIN(3), PETER SCHNOHR(4), GORM JENSEN(4), KNUT BORCH-JOHNSEN(5), THORKILD I. A. SORENSEN

Copenhagen Centre for Prospective Population Studies(*), Danish Epidemiology Science Centre,

Institute of Preventive Medicine, Copenhagen University Hospital, Kommunehospitalet, DK-1399, Copenhagen, Denmark

(1) The Danish Committee for the Assessment of Sub-standard Lives, Virum, Copenhagen, Denmark

(2) Alcohol Unit, Department of Medical Gastroenterology, Hvidovre Hospital, University of Copenhagen, Denmark

(3) The Copenhagen Male Study and

(4) The Copenhagen City Heart Study, Epidemiological Research Unit, Copenhagen University Hospital, Bispebjerg, Denmark

(5) Copenhagen County Centre of Preventive Medicine, Medical Department C, Glostrup University Hospital, Glostrup, Denmark

(*) See Acknowledgement.

Address correspondence to: M. Gronbaek. Fax: (+45) 3391 3244
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Author:GRONBAEK, MORTEN; DEIS, ALLAN; BECKER, ULRIK; HEIN, HANS OLE; SCHNOHR, PETER; JENSEN, GORM; BORCH-JO
Publication:Age and Ageing
Geographic Code:4EUDE
Date:Nov 1, 1998
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