Rationale & objective: Increasing evidence has linked ambient fine particulate matter (ie, particulate matter no larger than 2.5 μm [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 × 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, 1.58-1.85) per 10-μg/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.
Plain-language summary: Exposure to a form of air pollution known as fine particulate matter (ie, particulate matter ≤2.5 μm [PM2.5]) has been linked to an increased risk of chronic kidney disease (CKD), but little is known about how PM2.5 affects CKD in regions with extremely high levels of PM2.5 pollution. This longitudinal cohort study in China investigates the effect of PM2.5 on the incidence of CKD and whether temperature or humidity interact with PM2.5. Our findings suggest that long-term exposure to high levels of ambient PM2.5 significantly increased the risk of CKD in mainland China, especially in terms of cumulative average PM2.5. The associations of PM2.5 and incident CKD were greater in high-humidity environments. These findings support the recommendation that reducing PM2.5 pollution should be a priority to decrease the burden of associated health risks, including CKD.
Keywords: Air pollution; China; ambient temperature; chronic kidney disease (CKD); climate change; environmental risk factor; fine particulate matter (PM(2.5)); humidity; incident CKD; public health; renal function.
Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.