Evaluation of vulnerable PM_2.5-exposure individuals: a repeated-measure study in an elderly population

Numerous studies have shown that elderly people are susceptible to high-level particles with aerodynamic diameter ≤ 2.5 μm (PM_2.5) exposure. However, not all elderly people exposed to PM_2.5 suffer from diseases. In this study, we aim to establish a method to predict the vulnerable PM_2.5-exposure individuals among elderly population. Fourteen elderly people were recruited from May 8 to July 4, 2016, in Nanjing, China. Ten physiological indicators were repeatedly measured for 15 times. Liner mixed-effects model, principal component analysis (PCA), and PM_2.5 lag score were used to estimate the effects of PM_2.5 on blood pressure, pulse, and lung function. As a result, each quartile increase of ambient PM_2.5 was significantly associated with increased pulse (P < 0.05 for lag0, 1, 4, 0-1, 0-2, 0-3, and 0-5 days), decreased blood pressure (P < 0.05 for lag4 and 0-3 days), and decreased lung function (P < 0.05 for lag0, 1, 0-1, and 0-2 days) among the 14 elderly people. In terms of pulse or lung function, three elderly people were considered as vulnerable PM_2.5-exposure individuals. No vulnerable individual was found for blood pressure. Blood pressure, pulse, and lung function could be affected by high-level PM_2.5 exposure in elderly people. This method for screening three elderly people may provide a new insight on identifying the vulnerable PM_2.5-exposure individuals.