Table 4.
Estimated proportion of association between greenness and mortality in the Nurses’ Health Study explained by physical activity, air pollution exposure, social engagement, and mental healtha,b.
| Mediator | Proportion of association of cumulative average greenness in 250-m buffer explained by mediator (95% CI) | Proportion of association of cumulative average greenness in 1,250-m buffer explained by mediator (95% CI) |
|---|---|---|
| Total physical activity (< 3 MET hr/week vs. ≥ 3 MET hr/week) | 2.1% (0.2%, 19.3%) | 1.1% (0.1%, 15.8%) |
| Air pollution [modeled PM2.5 < 9.7 μg/m3 (quintile 1) vs. ≥ 9.7 μg/m3 (quintiles 2–5)] | 4.4% (2.4%, 7.7%) | 5.1% (2.4%, 10.5%) |
| Social engagement (participate in groups > 1 per week vs. ≤ 1 per week) | 19.1% (10.0%, 33.3%) | 12.8% (6.4%, 24.0%) |
| Mental health (physician-diagnosed or antidepressant use vs. none) | 30.6% (15.5%, 51.4%) | 25.5% (12.8%, 44.4%) |
| All mediators combined | 27.1% (14.7%, 44.6%) | 19.8% (10.2%, 35.0%) |
| Abbreviations: CI, confidence interval; MET, metabolic equivalent of task; PM2.5, particulate matter < 2.5 μm in aerodynamic diameter. aAnalyses adjusted for age and calendar year, race/ethnicity, smoking status, pack-years smoked, parental occupation, registered nurse (RN) degree, marital status, husband’s highest education, census-tract median home value, and census-tract median income. bMediation analyses assume that there is no unmeasured exposure–outcome confounding, no unmeasured mediator–outcome confounding, no unmeasured exposure–mediator confounding, and no mediator–outcome confounder affected by exposure. | ||