Lung function and measured glomerular filtration rate decline in the general population

Background The prevalence of chronic kidney disease (CKD) and respiratory diseases is rising. Reduced lung function contributes to hypoxia and low-grade inflammation, but its relationship to age-related decline in glomerular filtration rate (GFR) remains unknown. Methods In the Renal Iohexol Clearance Survey (RENIS), we repeatedly measured GFR (mGFR) using iohexol clearance over a median of 11 years in 1 837 individuals from the general population without self-reported diabetes, kidney disease, or cardiovascular disease. A linear mixed model examined the relationship between baseline lung function, measured by spirometry, and changes in mGFR. Logistic regression estimated the odds ratio (OR) for accelerated mGFR decline. Interval-censored Cox regression was used to estimate the hazard ratio (HR) for incident CKD. Results Lower %-predicted forced expiratory volume in 1 second (FEV1%) and %-predicted forced vital capacity (FVC%) were each associated with steeper mean mGFR decline. Per 10% decrease, the estimated difference in annual mGFR decline was − 0.05 mL/min/1.73 m²/year for FEV1% (95% confidence interval [CI] −0.09 to − 0.02) and − 0.05 mL/min/1.73 m²/year for FVC% (95% CI − 0.09 to 0.00). These associations were no longer significant after adjustment for smoking. In fully adjusted models, lower FVC% was associated with accelerated mGFR decline in men only (OR 1.32; 95% CI 1.11–1.57 per 10% decrease), and lower FEV1% was associated with incident CKD in men and women (HR 1.15; 95% CI 1.03–1.29). Conclusion Lower lung function was associated with steeper mGFR decline, largely attenuated after adjustment for smoking. Lower FEV1% remained associated with incident CKD.