Seasonal Variation in Temperature and Life-Space Mobility among Older Adults: A Pilot Study using Mobile Health Technology

Background and Objectives Extreme outdoor temperatures are known barriers to physical activity and may constrain life-space mobility, the geographic footprint of where people live, work, and recreate, and an important indicator of health and independence among older adults. We conducted a pilot study to evaluate the feasibility of a mobile health (mHealth) app designed to objectively capture life-space and to demonstrate its utility through a downstream analysis of ambient temperature and life-space mobility. Research Design and Methods Using data collected via an iPhone app from 82 participants in an ongoing cohort study (June 2023-January 2024), we used linear mixed-effects models to examine associations between daily average temperature and three objective life-space measures: ellipse area, maximum distance traveled, and total distance traveled. Models were stratified by season and adjusted for relative humidity and sociodemographic covariates. Results The app successfully captured high-resolution longitudinal mobility data over two weeks per participant. There was a significant negative nonlinear association between higher daily average temperature and life-space in the summer. With the peak life-space ellipse area observed at 28.8 °C, for every degree Celsius greater than 28.8 °C, we found a statistically significant decrease in ellipse area by 2.97 km2 (95% CI: -5.45, -0.51; p = 0.02). Findings were similar for the outcomes of maximum and total distances traveled. Discussion and Implications This study demonstrates that mHealth technology is a feasible tool for assessing life-space mobility in older adults. Higher temperatures are associated with lower life-space metrics, highlighting the potential of app-derived metrics as digital biomarkers for mobility research.