Associations of Ambient Air Pollution and Road-Related Environmental Characteristics with Cardiometabolic Health: The Role of Walking

Ambient air pollution and road environments may have contrasting associations with walking and cardiometabolic health. We examined these relationships in 4141 middle-aged and older adults from the third wave of the Australian Diabetes, Obesity and Lifestyle Study. Generalized additive mixed models estimated associations of residential PM2.5, NO2, total and major road density, and distance to the nearest busy road with cardiometabolic indicators and walking behaviors. Benjamini–Hochberg false discovery rate adjustment was applied within defined test families. Cross-sectional patterns involving walking were evaluated using an FDR-adjusted joint-significance criterion. PM2.5 was positively associated with diastolic blood pressure and non-linearly associated with systolic blood pressure; NO2 was non-linearly associated with systolic blood pressure. Total road density was associated with lower HDL cholesterol and higher triglycerides; major road density was associated with higher triglycerides and non-linearly with HbA1c. Distance to the nearest busy road was non-linearly associated with HbA1c. Higher road densities were associated with less total walking time among walkers, whereas higher PM2.5 and NO2 were associated with greater participation in walking for transport. Joint-significance patterns involved waist circumference and lipids. These findings highlight the importance of considering environmental exposures and walking together but do not establish temporal ordering or causal mediation.