UC Davis

BACKGROUND: Growing evidence suggests that neighborhood contextual environment could influence risk factors and, therefore, incidence of lethal prostate cancer. We studied the association between neighborhood greenness and lethal prostate cancer incidence and assessed mediation by vigorous physical activity. METHODS: A total of 47,958 participants were followed in the Health Professionals Follow-up Study from 1986 to 2014. Neighborhood greenness exposure was estimated using normalized difference vegetation index (NDVI) with 1 km resolution, assigned to home or work addresses at start of follow-up. Adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) were estimated using sequentially adjusted Cox models with individual and contextual prostate cancer risk factors as covariates. Analyses were compared among those whose addresses were constant over follow-up and stratified by population density and address type. RESULTS: We observed 898 cases over 1,054,743 person-years. An interquartile range increase in NDVI was associated with 5% lower rate of lethal prostate cancer (aHR = 0.95, 95% CI = 0.88, 1.03), with stronger associations in nonmovers (aHR = 0.92, 95% CI = 0.85, 1.01). Inverse associations were observed among men in high (aHR = 0.90, 95% CI = 0.82, 0.99) but not low (aHR = 1.11, 95% CI = 0.95, 1.29, P het = 0.086) population density areas, and those reporting from work (aHR = 0.87, 95% CI = 0.75, 1.01) but not home (aHR = 1.04, 95% CI = 0.91, 1.17, P het = 0.10) addresses. There was no evidence of mediation by vigorous physical activity. CONCLUSION: We report inverse associations between neighborhood greenness and lethal prostate cancer when restricting to nonmovers and in high population density areas. Replication could confirm findings and clarify mechanisms.