Mediation analysis of the associations between neighbourhood walkability and greenness, accelerometer-measured physical activity, and health-related fitness in urban dwelling Canadians

Objective: To estimate sex-specific associations (total, direct, and indirect effects) between objectively measured neighbourhood walkability and greenness and objectively measured physical activity and health-related fitness including cardiorespiratory and muscular fitness in Canadian adults.Methods: Neighbourhood walkability (Canadian Active Living Environment) and greenness (Normalized Difference Vegetation Index; NDVI) data were linked to cardiorespiratory (i.e., submaximal step test estimated VO2 max) and muscular fitness (i.e., handgrip strength) and accelerometer measured physical activity; Canadian Health Measures Survey). Covariate-adjusted sex-stratified path analyses was conducted to assess if physical activity (light: LPA; moderate: MPA, and; vigorous: VPA) mediated the associations between neighbourhood walkability, NDVI and health-related fitness. Model sample sizes ranged from 987 to 2796 for males and 989 to 2835 for females.Results: Among males, we found indirect effects between neighbourhood walkability and cardiorespiratory fitness via LPA (negative) and VPA (positive). We also found a total effect (negative) between neighbourhood walkability and grip strength and indirect effects between neighbourhood walkability and handgrip strength via LPA (negative) and MPA (negative). Among females, we found a total effect (positive) and direct effect (positive) between neighbourhood walkability and cardiorespiratory fitness, and an indirect effect for neighbourhood walkability and cardiorespiratory fitness via LPA. We found no significant effects related to neighbourhood greenness.Conclusions: Residing in a neighbourhood with higher walkability may positively affect cardiorespiratory fitness but negatively affect muscular strength. The negative associations between neighbourhood walkability and LPA may offset potential positive associations between neighbourhood walkability and MPA and VPA and their subsequent influence on health-related fitness.