Dual-career families--is there any impact on children's physical activity and risk of obesity?

To the Editor: Last month the federal government released its strategy to prevent childhood obesity (1). With so many Australian children now overweight or obese (2) action is urgently required (3). It is well recognised that energy balance is the key to maintaining healthy weight; however the government's strategy appears to put an emphasis on increasing physical activity mainly in out-side-of-school hours care facilities, with few resources allocated to promoting healthy eating. Once again, the nutrition side of the energy equation appears to be the missing ingredient in the national effort to prevent obesity (4). The focus on increasing physical activity among children who attend out-of-school hours care suggests there are concerns that these children are less likely than other children to be adequately active and more likely to be overweight or obese, presumably because both their parents are working and have less time to support and encourage their children to play sport and be active.

The rise in the number of dual-career families does coincide with increases in childhood obesity in this country. In 2002, more than half of all couple families (57%) with children aged less than 15 years were dual-career families; reflecting an increase from 61% to 71% in women's participation in the labour force since 1986 (5). It is not unreasonable to suggest that children from dual-career families may experience fewer opportunities to be physically active compared to children from single-career families. For example, in the US, it has been argued that children in dual-career families may spend greater amounts of time in unsupervised, indoor pursuits, such as television (TV) viewing and electronic-games use due to parent safety concerns, and restrictions on parent's time to support, encourage and supervise their children in physical activity (6,7).

Using data collected in 2001 (8), we investigated the relationship between parents' working status and children's TV viewing, physical activity and body mass index (BMI). Families were recruited from 19 state primary schools in high and low socio-economic areas across Melbourne. Physical activity was objectively assessed using accelerometers among 294 children aged five to six years and 926 children aged ten to 12 years. Information on sociodemographic background, parent employment status and time spent watching TV was collected via a questionnaire completed by parents. Children's height was assessed with a portable stadiometer and weight was assessed using digital scales. BMI z-scores were calculated using the LMS method developed by the International Obesity Task Force (9). We examined the data to determine whether children from dual-career families had lower levels of physical activity, spent more time watching TV, and were more likely to be overweight or obese than children from single-career families. For the purposes of analysis, single parent families in which the parent worked were classified along with dual-career families on the basis that the constraints on the parent (for example time constraints) would be similar to those on dual-career families.

Analysis of co-variance, adjusting for maternal and paternal education levels and age of the child, did not reveal any significant differences by parent working status in the children's average daily physical activity, in the average time spent in sedentary, light, moderate or vigorous-intensity activity or in the average time spent watching TV (Table 1). There were also no differences between dual-career and single-career families in children's BMI z-score (Table 1), nor in the prevalence of overweight or obesity among children in this study sample (data not shown). Our findings do not support the concern that children from dual-career families face a greater risk of obesity or inactivity. This is possibly because children in after school hours care receive adequate opportunities to be active, or unsupervised children not in formal care arrangements play more freely (10) or are more involved in organised sports (6).

Out-of-school hours care is one potentially important setting in which to promote physical activity. However, if the federal government is serious about preventing childhood obesity, it needs to provide resources that will allow the community to tackle inactivity and poor eating habits together for longer than a single parliamentary term, and to do so across multiple settings. A short-term focus on just one setting (or just on families in which both parents work), is unlikely to have any significant impact on the epidemic.

Table 1. Mean daily participation in physical activity and television
(TV) viewing, and BMI z-scores for single-career and dual-career
families, by sex of the child (a)

                                 Boys
                         n    Mean ([+ or -]SD)        P value

Movement counts/day (b)
Single-career families   202    5.89 ([+ or -] 0.32)   0.985
Dual-career families     298    5.89 ([+ or -] 0.30)

Sedentary mins/day
Single-career families   202  946.42 ([+ or -] 95.12)  0.244
Dual-career families     298  940.46 ([+ or -] 87.12)

Light mins/day
Single-career families   202  317.77 ([+ or -] 80.15)  0.869
Dual-career families     298  325.59 ([+ or -] 74.86)

Moderate mins/day
Single-career families   202  146.51 ([+ or -] 59.18)  0.023
Dual-career families     298  145.37 ([+ or -] 58.80)

Vigorous mins/day
Single-career families   202   29.30 ([+ or -] 16.90)  0.588
Dual-career families     298   28.58 ([+ or -] 17.63)

TV mins/day
Single-career families   215  132.61 ([+ or -] 68.65)  0.695
Dual-career families     311  131.08 ([+ or -] 63.67)

BMI (c)
Single-career families   218    0.56 ([+ or -] 0.91)   0.293
Dual-career families     317    0.49 ([+ or -] 0.99)

                                 Girls
                         n    Mean ([+ or -]SD)        P value

Movement counts/day (b)
Single-career families   211    5.78 ([+ or -] 0.30)   0.137
Dual-career families     361    5.82 ([+ or -] 0.32)

Sedentary mins/day
Single-career families   211  944.85 ([+ or -] 71.33)  0.715
Dual-career families     361  952.36 ([+ or -] 84.68)

Light mins/day
Single-career families   211  340.56 ([+ or -] 68.34)  0.392
Dual-career families     361  345.27 ([+ or -] 76.61)

Moderate mins/day
Single-career families   211  134.82 ([+ or -] 60.84)  0.898
Dual-career families     361  121.93 ([+ or -] 53.72)

Vigorous mins/day
Single-career families   211   19.77 ([+ or -] 13.79)  0.068
Dual-career families     361   20.44 ([+ or -] 17.39)

TV mins/day
Single-career families   218  127.08 ([+ or -] 69.12)  0.349
Dual-career families     366  128.55 ([+ or -] 71.71)

BMI (c)
Single-career families   221    0.38 ([+ or -] 0.97)   0.192
Dual-career families     372    0.40 ([+ or -] 1.00)

(a) All analyses controlled for maternal education, paternal education
and age group of child.
(b) Log transformed data.
(c) Based on z-scores.

References

1. Department of Prime Minister and Cabinet. Building a Healthy Active Australia [Press release]. Canberra, 29 June 2004.

2. Magarey AM, Daniels LA, Boulton TJ. Prevalence of overweight and obesity in Australian children and adolescents: reassessment of 1985 and 1995 data against new standard international definitions. Med J Aust 2001;174:561-4.

3. Crawford D. Population strategies to prevent obesity [Editorial]. BMJ 2002;325:728-9.

4. Crawford D. Tackling the obesity epidemic--is nutrition the missing ingredient? [Editorial]. Nutr Diet 2002;59:172.

5. Australian Bureau of Statistics. Australian social trends, family and community--Family functioning: Balancing family and work. Canberra: Australian Bureau of Statistics; 2003.

6. Anderson PM, Butcher KF, Levine PB. Maternal employment and overweight children. J Health Econo 2003;22:477-504.

7. Anderson PM, Butcher KF, Levine PB. Economic perspectives on childhood obesity. Economic Perspectives 2003;3Q:30-48.

8. Timperio A, Crawford D, Telford A, Salmon J. Perceptions about the local neighbourhood and walking and cycling among children. J Prev Med 2004;38:39-47.

9. Cole TJ, Bellizi MC, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 2000;320:1240-3.

10. Sallis JF, Alcaraz JE, McKenzie TL, Hovell MF, Kolody B, Nader PR. Parental behavior in relation to physical activity and fitness in 9-year-old children. Am J Dis Child 1992;146:1383-8.

D. Crawford, Associate Professor

S. Robinson, Dr J. Salmon Research Fellow

Centre for Physical Activity and Nutrition Research

Deakin University, Melbourne