Weather variation in objectively measured physical activity: results of four Brazilian cohorts

Background: The aim of the present study was to examine the relationship of objectively measured physical activity and weather variables in different stages of life course. Methods: This study used data from four Brazilian cohorts (mean ages: 10.9, 22.6, 30.2, and 70.5 years). The exposure was weather variation, using temperature, rain, humidity, and wind velocity. The outcome measured was accelerometer based physical activity in three ways: overall, 5-minute bouts, and 10-minute bouts physical activity. Both exposure and outcome were collected from the same period. Crude and adjusted analyses were fitted using a two-part model. Results: Among 9,966 individuals from different ages evaluated, physical activity levels were low, especially in older adults. Rain and mean wind velocity were not associated physical activity of individuals, however, the probability of children being inactive was higher during humid days. After mutually adjusting the models for weather variables, only mean temperature and humidity were associated with higher and lower physical activity levels in children, respectively. Conclusions: Weather variables are not key indicators to be accounted when modelling physical activity studies in almost all ages. However, this study helps to identify specifically exposures, regardless of the physical activity operationalization.