Exposure to particulate air pollution and long-term incidence of frailty after myocardial infarction

Purpose: Frailty, a multidimensional syndrome of increased vulnerability, is prevalent post-myocardial infarction (MI) and predicts mortality and recurrent events. We investigated whether chronic exposure to particulate matter ≤2.5μm in diameter (PM_2.5) is associated with the development of post-MI frailty. Methods: Participants (n= 1120) were aged 65 or less and admitted to hospital in central Israel with first MI in 1992 and 1993. Daily measures of PM_2.5 recorded at air quality monitoring stations were summarized and chronic exposure was estimated individually using the geo-coded residential location. Frailty assessment was conducted via an index based on deficit accumulation, and those defined as frail (applying a threshold of ≥0.25) at baseline were excluded. Remaining participants who survived to follow-up 10 to 13years post-MI (n= 848) were reassessed for frailty. Logistic regression models were constructed to evaluate the role of PM_2.5 exposure in frailty risk prediction. Results: Mean exposure to PM_2.5 was 24.2μg/m³ (range, 16.9-28.6). A total of 301 participants (35.5%) developed frailty during follow-up. Adjusting for sociodemographic and clinical variables, PM_2.5 exposure was associated with increased odds of developing frailty (odds ratio, 1.53; 95% confidence interval, 1.22-1.91, comparing the 75th vs. 25th percentiles). Addition of PM_2.5 exposure to the multivariable model resulted in an integrated discrimination improvement of 1.60% (P= .005) and a net reclassification index of 6.51% (P= .02). Conclusions: An association was observed between exposure to PM_2.5 and incidence of frailty, providing a potential intermediary between air pollution and post-MI outcomes.