Long-term exposure to air pollution and chronic kidney disease incidence in adults: The Danish Nurse Cohort.
TL;DR
Positive associations between long-term exposure to NO2 and CKD incidence were greater in never smokers than in ever-smokers, and stronger associations among never-smokers suggest that environmental exposures may independently influence kidney health.
Abstract
Background
Air pollution is an established risk factor for cardiovascular and metabolic diseases, but evidence on chronic kidney diseases (CKD) remains limited.
Objective
We aim to examine the association between long-term exposure to air pollutants and CKD incidence.
Methods
We followed 24,581 female nurses from the Danish Nurse Cohort, recruited in 1993 or 1999, for their first-ever hospital contact with a primary or secondary CKD diagnosis until 2018. We estimated annual mean levels of particulate matter with a diameter < 2.5 µm (PM2.5) and 10 µm (PM10), nitrogen dioxide (NO2), and black carbon (BC) at nurses' residential addresses using the DEHM/UBM/AirGIS modeling system. We used Cox regression models to examine the association of 14-year running means of air pollutants with CKD incidence and to explore the effect modification of this association by lifestyles.
Results
Over 521,211 person-years of follow-up, 429 nurses developed CKD. We found positive associations of modest magnitude between long-term exposure to air pollutants and CKD, with hazard ratios (95% confidence intervals) per interquartile range: 1.18 (0.93-1.50) per 2.86 µg/m3 for PM2.5, 1.14 (0.93-1.40) per 3.33 µg/m3 for PM10, 1.13 (0.99-1.28) per 8.09 µg/m3 for NO2, and 1.09 (1.00-1.20) per 0.34 µg/m3 for BC. The associations between long-term exposure to NO2 and CKD incidence were greater in never smokers than in ever-smokers. Associations with NO2 and BC remained unchanged in two-pollutant models, whereas those with PM10 and PM2.5 attenuated.
Significance
Our study adds important new findings to the growing evidence suggesting that air pollution may be associated with CKD incidence. IMPACT STATEMENT This study provides longitudinal evidence that long-term exposure to ambient air pollution contributes to chronic kidney disease (CKD) incidence, even in a relatively healthy occupational cohort and at comparatively low pollution levels. Although effect sizes were modest, consistent positive associations, particularly for NO2 and black carbon, highlight traffic-related pollution as a potential renal risk factor. Stronger associations among never-smokers suggest that environmental exposures may independently influence kidney health. These findings reinforce the need to integrate air pollution into CKD risk assessment and prevention strategies. Strengthening air quality policies and reducing long-term residential exposure could help lower CKD burden and protect kidney health at the population level.