Association of Long-term Ambient Fine Particulate Matter (PM2.5) and Incident CKD: A Prospective Cohort Study in China

Rationale & Objective: Increasing evidence has linked ambient fine particulate matter (ie, particulate matter no larger than 2.5 mu m [PM2.5]) to chronic kidney disease (CKD), but their association has not been fully elucidated, especially in regions with high levels of PM2.5 pollution. This study aimed to investigate the long-term association of high PM2.5 exposure with incident CKD in mainland China. Study Design: Prospective cohort study. Setting & Participants: 72,425 participants (age =18 years) without CKD were recruited from 121 counties in Hunan Province, China. Exposure: Annual mean PM2.5 concentration at the residence of each participant derived from a long-term, full-coverage, high-resolution (1 x 1 km2), high-quality dataset of ground-level air pollutants in China. Outcomes: Incident CKD during the interval between the baseline examination of each participant (2005-2017) and the end of follow-up through 2018. Analytical Approach: Cox proportional hazards models were used to estimate the independent association of PM2.5 with incident CKD and the joint association of PM2.5 with temperature or humidity on the development of PM2.5-related CKD. Restricted cubic splines were used to model exposure-response relationships. Results: Over a median follow-up of 3.79 (IQR, 2.03-5.48) years, a total of 2,188 participants with incident CKD were identified. PM2.5 exposure was associated with incident CKD with an adjusted hazard ratio of 1.71 (95% CI, 1.581.85) per 10-mu g/m3 greater long-term exposure. Multiplicative interactions between PM2.5 and humidity or temperature on incident CKD were detected (all P < 0.001 for interaction), whereas an additive interaction was detected only for humidity (relative risk due to interaction, 3.59 [95% CI, 0.97-6.21]). Limitations: Lack of information on participants' activity patterns such as time spent outdoors. Conclusions: Greater long-term ambient PM2.5 pollution is associated with incident CKD in environments with high PM2.5 exposure. Ambient humidity has a potentially synergetic effect on the association of PM2.5 with the development of CKD.