How air pollution relates to chronic pain in middle-aged and older adults: a Nationwide cohort study

Objectives This study aimed to investigate the longitudinal associations between chronic pain and NO2, O3, PM1, PM2.5 and PM10 amongst middle-aged and older Chinese adults. Methods This cohort study included 10 616 Chinese participants aged≥45 years. The participants were followed up in five waves between 2011 and 2020. Chronic pain and the affected sites were identified using questionnaires. Participants and air pollution data were matched based on geographic location. Data were obtained from the China Health and Retirement Longitudinal Study and China High Air Pollutants datasets. After adjustment for confounders, time-varying Cox models were used to explore the pain-pollutant association. The linear relationships between air pollutants and general pain risk were tested using exposure-response analysis. Subgroup analyses were conducted based on the affected body sites. Multi-pollutant models were used to explore potential interactions between pollutants. Results Every 10 μg/m3 increase in NO2 (HR = 1.116, 95% CI: 1.051 to 1.186), PM1 (HR = 1.185, 95% CI: 1.112 to 1.265), PM2.5 (HR =1.122, 95% CI: 1.080 to 1.165), and PM10 (HR = 1.089, 95% CI: 1.062 to 1.117) corresponded to a 11.6%, 18.5%, 12.2%, 8.9% higher risk of chronic pain, respectively. O3 significantly increased the risk of chronic headache (HR = 1.018, 95%CI: 1.022 to 1.221). Abdominal and chest pain was only associated with PM2.5. PM pollutants suppressed the effects of NO2, whereas O3 did not influence the effects of other pollutants. Conclusions There were linear associations between multiple air pollutants and the risk of chronic pain. This study emphasised the importance of improving air quality for healthy ageing.