CHRONIC KIDNEY DISEASE IN PRIMARY CARE AND THE RISK OF CARDIOVASCULAR COMORBIDITY AND MORTALITY

Abstract BACKGROUND AND AIMS The prevalence of chronic kidney disease (CKD) is increasing globally. Often, the condition develops silently over time, with no or only a few symptoms in earlier stages. Therefore, early recognition in primary care may have an important role in ensuring diagnosis and proper intervention. We aimed to determine the prevalence and outcome of CKD in a large primary care cohort in Denmark. METHOD We performed an observational cohort study using data from individuals above age 40 followed in primary care in the greater Copenhagen area between 2000 and 2015 and linked them to Danish health registries. A run-in period of 3 months was included to ensure stable conditions and rule out acute changes in eGFR at baseline. The date of the second measurement of eGFR during the study period was considered the subject's index date (baseline). Outcomes were relevant diagnoses such as stroke, myocardial infarction (MI), hospitalisations for heart failure (HHF) and peripheral artery disease (PAD) (last update 2018), all-cause mortality and cardiovascular mortality. Kidney function (eGFR) was estimated by the CKD-EPI formula based on serum creatinine and expressed in mL/min/1.73 m2. Conventional CKD groups are used with CKD 1 and 2 (normal—eGFR > 60 mL/min/1.73 m2) as reference groups for the hazard ratio estimates. Outcomes were presented as the number of events/100 person-years (PY). We conducted survival (all-cause mortality outcome) and competing risk (rest of the outcomes) analyses using the Cox proportional hazards model to calculate the (cause-specific) hazard ratios for the outcomes according to CKD group. We further explored the continuous associations between kidney function and the outcomes examined by using eGFR as a continuous variable with penalised splines. All models were adjusted for known risk factors (age, gender, diabetes, hypertension, existing CVD, heart failure, LDL cholesterol, use of antihypertensive treatment). RESULTS We included a population of 171 133 individuals. As expected, the majority (n = 157002) was in CKD 1 or 2 at the index date, and only a small proportion (0.05%) was in CKD stage 5. In general, event rates were low in CKD stages 1 and 2 and rose with higher stages of CKD. In the adjusted analyses, we observed a stepwise increase in hazard rates for every outcome with every increment in CKD stage (Fig. 1). This was confirmed by the continuous analysis. Compared with CKD stage 1 + 2, individuals in CKD stage 4 had approximately double the hazard rate of PAD, MI, cardiovascular and all-cause mortality. CONCLUSION Our data from a large primary care cohort demonstrate an early increase in risk for adverse outcomes already at CKD stage 3. This provides the basis and underlines the importance of studying early intervention in primary care.