Intraregional differences in renal function in the Northern Netherlands: The Lifelines Cohort Study

BACKGROUND: Although the interregional disparity in chronic kidney disease (CKD) prevalence has been reported globally, little is known about differences in CKD prevalence within a region. We aimed to study the intraregional distribution of renal function in the Northern Netherlands and identify determinants of geographical differences in renal function. METHODS: We included 143,735 participants from the Lifelines population-based cohort in the Northern Netherlands. Spatial analysis was performed to identify regional clusters of lower eGFR (cold spots) and higher eGFR (hot spots) at the postal code level, without and with adjustment for clinical risk factors. Multivariate logistic regression was used to identify the contribution of neighborhood-level health-related behaviors, socioeconomic status, and environmental factors (air pollution parameters, urbanity) to regional clustering of lower eGFR. RESULTS: Significant spatial clustering of renal function was found for eGFR as well as for early stage renal function impairment (eGFR<90 ml/min/1.73 m(2)), (p<0.001). Spatial clustering persisted after adjustment of eGFR for clinical risk factors. In adjusted cold spots, the aggregate eGFR was lower (mean ± SD: 96.5±4.8 vs. 98.5±4.0 ml/min/1.73 m(2), p = 0.001), and the prevalence of early stage renal function impairment (35.8±10.9 vs. 28.7±9.8%, p<0.001) and CKD stages 3–5 was higher (median (interquartile range): 1.2(0.1–2.4) vs 0(0–1.4)%, p<0.001) than in hot spots. In multivariable logistic regression, exposure to NO(2) (Odd ratio [OR], 1.45; 95% confidence interval [95% CI], 1.19 to 1.75, p<0.001) was associated with cold spots (lower renal function), whereas proportion of fat intake in the diet (OR, 0.68; 95%CI, 0.48–0.97, P = 0.031) and income (OR, 0.91; 95%CI, 0.86–0.96, p<0.001) for median level income) were inversely related. CONCLUSIONS: Significant intraregional clustering of renal function, early renal function impairment and CKD were observed in the Northern Netherlands even after adjustment for renal function-related clinical risk factors. Environmental (air pollution), neighborhood-level socioeconomic factors and diet are determinants of intraregional renal function distribution. Spatial analysis might be a useful adjunct to guide public health strategies for the prevention of CKD.