The Associations of Joint Exposure to Various Living Environmental Factors with the Risk of Frailty and All-cause Mortality: A Nationally Representative Cohort Study

Background The relationships of joint exposure to various outdoor and indoor environmental factors with the risk of frailty and mortality remain unclear. Methods Based on the China Health and Retirement Longitudinal Study, we enrolled 13 745 participants in the final analysis. The living environmental score incorporated 7 factors: ambient fine particulate matter, residential greenness, household fuel use, indoor temperature, water sources, building types, and household cleanliness (ranged from 0 to 8). Frailty was assessed by a 40-item deficit-accumulation frailty index. Cox proportional hazards regressions were used to assess the longitudinal associations of individual and joint exposure to living environmental factors with risk of frailty and mortality. Results In this prospective study, 3 389 participants developed frailty and 815 died during a 7-year follow-up. A higher living environmental score was linked to reduced risks of frailty (hazard ratio: 0.872, 95% CI: 0.854-0.890) and mortality (hazard ratio: 0.893, 95% CI: 0.856-0.932). Population-attributable fraction analyses revealed that 23.5% of frailty and 17.2% of deaths could be attributed to lower living environmental scores. For single factors, solid fuel use and PM_2.5 exposure had the greatest attribution to incident frailty and all-cause mortality, respectively. The effects of low living environmental score on all-cause mortality were mediated via frailty. Conclusions Multiple living environmental risk factors were separately and jointly associated with increased risks of frailty and mortality in an additive manner, emphasizing the importance of comprehensively assessing various environmental factors to promote healthy aging.