Long-Term Exposure to Air Pollution and Increased Risk of Membranous Nephropathy in China

Abstract

The effect of air pollution on the changing pattern of glomerulopathy has not been studied. We estimated the profile of and temporal change in glomerular diseases in an 11-year renal biopsy series including 71,151 native biopsies at 938 hospitals spanning 282 cities in China from 2004 to 2014, and examined the association of long-term exposure to fine particulate matter of <2.5 μm (PM_2.5) with glomerulopathy. After age and region standardization, we identified IgA nephropathy as the leading type of glomerulopathy, with a frequency of 28.1%, followed by membranous nephropathy (MN), with a frequency of 23.4%. Notably, the adjusted odds for MN increased 13% annually over the 11-year study period, whereas the proportions of other major glomerulopathies remained stable. During the study period, 3-year average PM_2.5 exposure varied among the 282 cities, ranging from 6 to 114 μg/m³ (mean, 52.6 μg/m³). Each 10 μg/m³ increase in PM_2.5 concentration associated with 14% higher odds for MN (odds ratio, 1.14; 95% confidence interval, 1.10 to 1.18) in regions with PM_2.5 concentration >70 μg/m³ We also found that higher 3-year average air quality index was associated with increased risk of MN. In conclusion, in this large renal biopsy series, the frequency of MN increased over the study period, and long-term exposure to high levels of PM_2.5 was associated with an increased risk of MN.

Keywords: air pollution; membranous nephropathy; renal biopsy.

Figure 1.

Trends in frequency of the most common glomerulopathies in China from 2004 to 2014. Open circles represent the unadjusted disease proportions among all glomerulopathies. Solid lines indicate the disease proportions estimated from generalized additive logistic models adjusted for age, gender, clinical syndromes, hospital type, pathologic laboratory, and region and weighted by regional population. Red lines and the corresponding gray zones, specify the ORs of the disease and their 95% CIs estimated from the generalized additive model with year 2009 as the reference.

Figure 2.

PM_2.5 was associated with odds for MN. (A) Two-dimensional smoothed map of the age- and gender-adjusted proportion of MN in 2014. Dots represent the locations of the hospitals performing the renal biopsies. (B) Map of 10-year average of PM_2.5 derived from satellite AOD. (C, E, and F) Smooth curves of the odds for MN along AOD-based PM_2.5 (C), ground-based PM_2.5 in 2014 (E), and average AQIs during 2012–2014 (F), respectively. The gray zones denote the 95% CI. (D) Average annual increases in odds for MN stratified by levels of PM_2.5 slope (rate of annual PM_2.5 increase), as estimated from the generalized additive models with adjustment for age, gender, clinical syndromes, hospital level, and pathologic laboratory, and with or without adjustment for region.