Background: Higher residential greenness seems to be associated with more physical activity (PA), but it remains unclear whether exposure to greenness outside the residential area associates with PA. Therefore, we investigated the association between activity space greenness and PA before and after retirement.
Methods. This longitudinal study is based on data from the Finnish Retirement and Aging study (FIREA). We included participants with at least two valid (≥10-h) days of accelerometer and GPS measurement (SenseDoc 2.0) both before and after retirement (n = 123, mean age 63.3 [SD 1.0] years, 82 % women). PA was expressed as light, moderate-to-vigorous (MVPA), total PA, and transportation PA. Activity space for each participant and time-weighed exposure to greenness was calculated using GPS-data and normalized difference vegetation index (NDVI) from satellite images. Cross-sectional associations between exposure to greenness and PA were examined on workdays and days off before retirement and on retirement days. Longitudinal changes in PA from workday to retirement day were analyzed in the exposure to greenness change groups (low, high, increase, or decrease).
Results: On workdays but not on days off or retirement, higher exposure to greenness was associated with less MVPA [β = −0.23 (95% CI: 0.44, 0.02)] and transportation PA [β = −0.27 (−0.47, −0.08)]. MVPA and transportation PA increased among all participants from workday to retirement [6.1 (1.7, 10.5) min/day, and 7.8 (3.6, 11.9) min/day, respectively]. However, the changes in exposure to greenness were not associated with the changes in light PA, MVPA, or transportation PA.
Conclusion: While higher exposure to greenness based on NDVI was associated with less MVPA and transportation PA on workdays, the changes in exposure to greenness were not associated with the changes in PA.