Background It is unclear which weather parameters effect the motion-sensor-based measurement of physical activity in terms of walking duration in older people.

Methods Between March 2009 and April 2010, the physical activity of 1324 German community-dwelling older people (≥65 years, 56.4% men) was recorded over 5 days using accelerometers. Multilevel linear regression analysis was used to estimate the effect of local daily weather parameters (daylight, maximum temperature, total global radiation, average precipitation, average wind speed and average humidity) on walking duration.

Results Mean daily walking duration was comparable for men and women, with 104.4±50.7 min and 102.9±47.8 min, respectively. A linear relationship with walking duration was seen for all considered weather parameters. The strongest effect was found for global radiation, which involved an increase in walking duration of 16.1 min in men and 19.2 min in women between an average winter day (with about 0.8 kWh/m² radiation) and an average summer day (with about 6 kWh/m² radiation); similar patterns were found for daily maximum temperature and daylight. Furthermore, physical activity decreased significantly with increasing wind speed, precipitation and humidity.

Conclusions Studies on physical activity in community dwelling older people should consider weather conditions.