Abstract
Currently the Chinese government has adopted World Health Organization interim target-1 values as the national ambient air quality standards values. However, the population-based evidence was insufficient, especially for the oldest old (aged 80+). We evaluated the association of fine particulate matters (PM2.5) exposure and incidence of disability in activities of daily living (ADL) in 15 453 oldest old in 886 counties/cities in China from 2002 to 2014 using Cox model with penalized splines and competing risk models to evaluate the linear or non-linear association. After adjusting for potential confounders, a J-shaped association existed between PM2.5 exposure with a threshold concentration of 33 μg/m3, and incident disability in ADL. Above this threshold, the risk magnitude significantly increased with increase of PM2.5 concentrations; compared to 33 μg/m3, the hazard ratio ranged from 1.03 (1.00–1.06) at 40 μg/m3 to 2.25 (1.54–3.29) at 110 μg/m3. The risk magnitude was not significantly changed below this threshold. Each 10 μg/m3 increase in PM2.5 exposure corresponded to a 7.7% increase in the risk of disability in ADL (hazard ratio 1.077, 95% CI 1.051–1.104). Men, smokers, and participants with cognitive impairment might be more vulnerable to PM2.5 exposure. The study provided limited population-based evidence for the oldest old and detected a threshold of 33 μg/m3, and supported that reduction to current World Health Organization interim target-1value (35 μg/m3) and Chinese national ambient air quality standards (35 μg/m3) or lower may be associated with lower risk of disability in ADL.
Highlights
Worldwide, aging-related physical disability has become a critical health concern with the rapidly growing number of older adults, who comprise the largest group of people with disabilities[1]
Several knowledge gaps are identified in the prior literature: (1) prior studies mainly focused on older adults younger than age 80 years, it is likely that adults within an older cohort may be extremely vulnerable to the negative effects of air pollution exposure given functional organ decline13. (2) previous studies have mainly focused on either a composite air pollution index (API) or nitrogen oxides (NOx) but have not assessed fine matter with a diameter
Our study adds to the current limited evidence of an adverse effect of PM2.5 on physical functioning in oldest old; to our knowledge, this is the first cohort study to demonstrate the association for this specific age group
Summary
Worldwide, aging-related physical disability has become a critical health concern with the rapidly growing number of older adults, who comprise the largest group of people with disabilities[1]. In China, the population aged 60 years and older with physical disability is predicted to reach 64.02 million by 2020, and 140 million by 20502, 3. Several knowledge gaps are identified in the prior literature: (1) prior studies mainly focused on older adults younger than age 80 years, it is likely that adults within an older cohort may be extremely vulnerable to the negative effects of air pollution exposure given functional organ decline. (5) Prior studies were mainly cross-sectional study in design, or only accounting for acute effects of short-term exposures, while disability in activities of daily living (ADL) would be expected to relate to chronic, progressive effects of long-term exposure to air pollution. We were able to access monitoring data throughout China, using satellite remote sensing combined with a nationwide networking of PM2.5 monitoring15. (5) Prior studies were mainly cross-sectional study in design, or only accounting for acute effects of short-term exposures, while disability in activities of daily living (ADL) would be expected to relate to chronic, progressive effects of long-term exposure to air pollution16. (6) Prior studies used different measures of disability; and an internationally accepted measure was not used, such as Katz index of independence in ADL 17
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