Association of air quality improvement and frailty progression: A national study across China

Abstract

Abstract Introduction More and more evidence shows that air pollution has an adverse effect on frailty. However, it’s little known about the effect of air pollution on frailty progression. Purpose With a strict clean air action implemented in China, we aimed to investigate whether improvements in air quality can alleviate the frailty progression. Methods This study involved 12891 participants with geocoded environmental data from the national wide China Health and Retirement Longitudinal Study (CHARLS) between wave 1 (2011) to wave 3 (2015). Average exposure to air pollutants (PM1, PM2.5, PM10, NO2, and O3) were estimated by satellite-based spatiotemporal approaches and matched with the residence. Air pollution improvements was defined as absolute changes of air pollutants (Δambient air pollutants = ambient air pollutants in 2011 – ambient air pollutants in 2015). Frailty progression was calculated by frailty index (FI) change (ΔFI=FI 2015-FI 2011) which was based on 53 items of the questionnaire covering physical limitations, psychological symptoms, comorbidities, history of trauma and cognitive impairment from wave 1 to wave 3. Multivariate logistic regression models were used to analyze the associations of air pollution improvements and the frailty progression, and restricted cube splines were used to exam possible nonlinear relationships between them. Results Compared to the lowest (Q1) quartile of PM1 exposure reduction, the highest (Q4) reduction was associated with the lowest risk for frailty progression after fully adjusting for confounders [aOR (95% CI)=0.75（0.68∼0.84）]. Similar protective effects of frailty progression were observed with the improvement of the air quality in PM2.5, PM10, and NO2 index, with aORs ranging 0.72-0.79 (Q4 vs Q1 of level reduction), while the reduction in O3 level appeared to be less related to changes in frailty progression [aOR=0.94（0.85∼1.04）]. The restricted cubic spline showed a dose response for the protective effect of improving of air quality and frailty progression. Conclusions The air quality improvement in PM1, PM2.5, PM10, and NO2, could alleviate the progression of frailty, while a reduction in O3 may not. This study is the first to examine the association between air pollution and the progression of frailty, sheading lights into the prevention of frailty in a national wide population.Odds ratios (95% CI) for main outcomeThe restricted cubic spline