Abstract
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.
Highlights
As population ageing progresses in developed countries, including Japan, the numbers of patients with chronic kidney disease (CKD) and chronic pulmonary obstructive disease (COPD) increase
These results indicate that the association of airflow limitation (AFL) with CKDcys seems to be stronger than their association with CKDcr
We showed for the first time that CKDcys and AFL are likely to overlap in community-based populations and that the overlap of AFL and CKDcys additively increases the risk of all-cause mortality
Summary
As population ageing progresses in developed countries, including Japan, the numbers of patients with chronic kidney disease (CKD) and chronic pulmonary obstructive disease (COPD) increase. For patients with lean muscle mass who have reduced serum Cr production, eGFRcr might overestimate renal function, resulting in failure to detect the presence of CKD. In such cases, it is recommended to use other markers of renal function, such as serum cystatin C (CysC) and CysC-based. The association between CKD evaluated using eGFRcr or eGFRcys and COPD among community-based populations is unknown In this cohort study, we examined the association between CKD and AFL that characterises COPD and the effect of their overlap on mortality in a community-based population using serum Cr and CysC as markers of renal function
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