Examination of How Mall Visits Moderate the Impact of Adverse Weather on Daily Step Counts: A Multilevel Analysis Using Nationwide Data from a Smartphone Application.

Climate change has led to an increase in extreme weather events. Adverse weather conditions limit outdoor activities, reduce step counts, and negatively affect health. Malls offer a possible alternative for walking in such weather; however, their step-loss mitigating role remains unexplored. We analyzed data from 18,666 individuals aged ≥ 18 years (mean ± standard deviation: 48.0 ± 12.6; women: 71.5%), tracking daily step counts over a year using a smartphone application. Step count data were collected via devices owned by the participants and then transferred to the program database through the application. Multilevel mixed-effects linear regression was used to estimate the associations between daily step counts and various interaction terms, focusing on two-way interactions between mall visits and weather, and three-way interactions involving sociodemographic factors. On days with maximum temperatures of < 15 °C or ≥ 35 °C, as well as during rain, deep snow depth, or strong winds, step counts were lower. However, on days when malls were visited, step counts were 1,269 higher compared with those on non-visit days. This difference was more pronounced during adverse weather: < 15 °C, ≥ 35 °C temperature, 0.1-4.9 and > 5 mm precipitation, snow depth > 3 cm, and wind speeds > 2.50 m/s. Mall visits mitigated weather-related step count reductions, particularly among older adults, women, and low-density area residents who generally take fewer steps. These findings underscore the role of weather-independent spaces, such as malls, in mitigating step count reductions during adverse weather. Improving access to and promoting their use are essential for maintaining physical activity in such conditions.