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标题：Time Spent Outdoors at Midday and Children’s Body Mass Index
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作者：Elizabeth Milne ; Julie A. Simpson ; Robyn Johnston 等
期刊名称：American journal of public health
印刷版ISSN：0090-0036
出版年度：2007
卷号：97
期号：2
页码：306-310
DOI：10.2105/AJPH.2005.080499
语种：English
出版社：American Public Health Association
摘要：Objectives. We investigated whether the Kidskin sun protection intervention increased children’s body mass index by reducing the time spent outdoors at midday. Methods. The Kidskin sun protection intervention involved 1614 Australian school children assigned to 1 of 3 groups: a control group, a moderate-intervention group, or a high-intervention group. Schools in the control group received the standard health curriculum and schools in the intervention groups received a multicomponent intervention. Outcomes included time spent outdoors and nevus development (a marker of melanoma risk). Height and weight were measured at 3 time points. Body mass index was transformed into age- and gender-specific z scores; z scores at each age were modeled simultaneously. Time spent outdoors at ages 10 and 12 years was analyzed using a linear mixed effects modeling. Results. The proportion of children who were overweight or obese increased with age. The moderate-intervention and control groups had a minimal increase in z score over time, and the z score for the high-intervention group decreased over time. There were no differences among groups with respect to total time outdoors at any age. Conclusions. It is possible to reduce the time children spend outdoors when ultraviolet radiation is high without producing an unfavorable effect on the children’s body mass index. Childhood obesity is an independent risk factor for adult obesity and the associated health problems of type 2 diabetes, hypertension, and cardiovascular disease. 1 In many developed countries, there has been a large increase in the prevalence of childhood overweight and obesity in recent years. The prevalence of obesity has increased two- to threefold over 25 years in the United States, and by the same amount over 10 years in the United Kingdom. 2 In Australia, the prevalence of childhood overweight doubled, and that of obesity trebled between 1985 and 1995; 20% to 25% of children are currently being classified as overweight or obese. 3 Furthermore, data from the last 35 years indicate that the increase in obesity among children is accelerating. 1 It is not yet clear whether the increase is primarily because of higher energy intake, reduced physical activity, or both. 1 However, encouraging both a healthy diet and more physical activity is recognized as a key strategy to curb these disturbing trends. 4 Most interventions aimed at preventing or treating childhood overweight and obesity have been designed to improve children’s eating habits and increase their physical activity levels. 5 Children have been particularly encouraged to walk or ride bicycles to school and to spend less of their leisure time engaged in sedentary activities. 5 However, there is limited evidence that these interventions have been effective. 6 Over the past 25 years, there have also been a growing number of sun protection interventions designed to reduce children’s exposure to sun in an effort to reduce the incidence of skin cancer in adult life. 7 Many of these interventions have focused on reducing the time children spend outdoors in the middle of the day when solar ultraviolet radiation is most intense, typically between 10 am and 3 pm . Children have been encouraged to stay indoors and engage in a range of alternative indoor activities during these hours. 7 Messages promoted in interventions (“Stay indoors and keep out of the sun”) are aimed at reducing exposure to the sun and may be perceived as being at odds with messages aimed at increasing physical activity (“Go outside and be active”). For example, studies consistently report that the time children spend outdoors is highly correlated with their level of physical activity. 8 It is, therefore, plausible that adhering to the sun safety message could inadvertently have a detrimental affect on children’s body mass index (BMI). Results from our study—the Kidskin sun protection intervention trial, conducted in Perth, Western Australia, between 1995 and 2001—have been published. 9 ^– 13 In those articles, we reported that children who received the intervention spent less time outdoors in the middle of the day after both 2 years 9 and 4 years of the intervention. 13 We also reported that 2 years into the study, the total time spent outdoors was similar in the 3 study groups. 9 For this analysis, we examined whether, after 6 years, the Kidskin intervention had an effect on the total time children spent outdoors—and thus, on their opportunity to engage in physical activity—or on their weight relative to height.