Residential altitude, aerosol optical depth, and diagnostic composition of biopsy-confirmed renal diseases: a single-center renal biopsy study from Yunnan, China.

BACKGROUND

Residential altitude may influence human physiology and reflect broader environmental gradients, but its relationship with the diagnostic composition of biopsy-confirmed renal diseases remains unclear.

METHODS

We retrospectively studied patients undergoing native kidney biopsy at The First People's Hospital of Yunnan Province, China, between February 2023 and February 2026. Residential altitude was derived from geocoded permanent addresses and analyzed using altitude quartiles and continuous models per 500-m increase. Restricted cubic spline analyses were performed as exploratory analyses. Environmental exposures were assigned according to geocoded residential coordinates and matched to the calendar year of kidney biopsy. Logistic regression and Firth penalized logistic regression compared biopsy-confirmed ANCA-associated renal vasculitis with other biopsy-confirmed renal diagnoses, with an additional sensitivity analysis using an expanded clinical-or-pathological ANCA outcome.

RESULTS

Among 1,602 patients, 1,593 had available altitude data. The overall distribution of renal pathological diagnoses did not differ across altitude quartiles. Exploratory restricted cubic spline analyses showed no significant altitude association for most major diagnoses, whereas ANCA-associated renal vasculitis demonstrated an inverse overall association without evidence of nonlinearity. In the selected multivariable model adjusted for age, sex, BMI, and ethnicity, each 500-m increase in altitude was associated with lower odds of biopsy-confirmed ANCA-associated renal vasculitis relative to other biopsy diagnoses (OR 0.51, 95% CI 0.34-0.77; P = 0.001). Similar results were observed in Firth penalized logistic regression. The association was attenuated after additional adjustment for distance to Kunming and AOD.

CONCLUSIONS

In this single-center biopsy-based cohort from Yunnan, residential altitude was not associated with broad differences in the overall spectrum of renal pathological diagnoses. Biopsy-confirmed ANCA-associated renal vasculitis accounted for a lower relative proportion of biopsy diagnoses at higher residential altitude, but this association was attenuated after accounting for geographic and environmental factors. These findings suggest that altitude-related patterns in renal biopsy diagnoses may reflect combined geographic, environmental, and referral-related gradients and should be interpreted within the context of a hospital-based biopsy population.