Weather Conditions and Disparities in Physical Activity and Obesity in the United States
- Presenter:
Chair: Michael Hagan; Discussant: Chad Meyerhoefer Wed June 7, 2006 9:45-11:15 Room 121
Context: The adult obesity rate in the U.S. is now over 30 percent. Exercise has been shown to be an effective weight control device in carefully controlled randomized trials, but it is less clear whether interventions designed to encourage exercise are effective in real-world community settings. One environmental factor that may be important in real-world settings is the weather. Little is known about how sensitive exercise participation rates are to outdoor weather conditions. For many people, particularly those in lower socioeconomic status (SES) groups, perceived exercise options may become very limited during unpleasant (unusually hot, cold, or wet) weather. Information regarding the relationship between weather conditions, exercise, and obesity across SES groups would be valuable for policymakers, community planners, health professionals, and ordinary citizens.
Objectives: We analyze the effect of weather conditions on exercise participation and the effect of exercise participation on body weight.
Statistical Methods: We employ linear regression models, including models with year, state, and state*month fixed effects, to test how exercise participation responds to unusual weather conditions. We then employ a two-stage instrumental variable (IV) model to test the causal effect of exercise on body weight, with weather conditions serving as IVs for exercise.
Data: We examine nationally representative data from the Behavioral Risk Factor Surveillance System (BRFSS) during 1993-2001 in the United States (total N = approximately 1.5 million). Individual level BRFSS data include measures of body mass index (BMI), exercise activities, diet, and socioeconomic and demographic characteristics. Using interview dates in BRFSS, we link these data to recent local weather conditions, available from the National Climatic Data Center.
Results: Our analysis is ongoing. Preliminary results suggest a strong first stage relationship between weather conditions and physical activity.
Discussion: The results of this study will help inform current public health efforts to increase exercise and reduce obesity. We will improve understanding of whether interventions must account for the diverse weather conditions in this country across regions and the seasons, and whether such interventions should focus on certain SES groups.
