Association among chronic kidney disease, airflow limitation, and mortality in a community-based population: The Yamagata (Takahata) study.

Chronic kidney disease (CKD) and chronic obstructive pulmonary disease (COPD) are known risk factors for mortality. In this study, we examined the overlap of CKD and airflow limitation (AFL) that characterises COPD and its effect on 10-year mortality in a community-based population. This study included 1,233 health check-up participants (mean age, 63.7 years; 46.7% men). We defined serum creatinine-based CKD (CKDcr) and serum cystatin C-based CKD (CKDcys) as glomerular filtration rate <60 mL/min/1.73 m2, estimated using serum creatinine or cystatin C, and/or dipstick proteinuria ≥1+. AFL was defined as forced expiratory volume in 1 s to forced vital capacity ratio <70% on spirometry. Compared with subjects without AFL, those with AFL showed a significantly higher prevalence of CKDcys but not of CKDcr. Cox proportional hazard analysis adjusted for confounders showed that the hazard ratio (95% confidence interval) for all-cause mortality was 1.45 (0.77–2.63) in subjects with CKDcys alone, 1.29 (0.60–2.54) in those with AFL alone, and 2.94 (1.33–6.12) in those with both CKDcys and AFL, with subjects without both AFL and CKD as the reference. This study showed that AFL and CKDcys are strongly associated and that their overlap is a significant risk factor for mortality in community-based populations.