RELATIONSHIP BETWEEN BMI IN ADOLESCENCE, BMI TRAJECTORIES IN ADULTHOOD AND CHRONIC KIDNEY DISEASE OUTCOMES: POPULATION-BASED COHORT STUDY

Abstract

Objective: We aimed to investigate the association of BMI in late adolescence and BMI trajectories in adulthood with chronic kidney disease (CKD), end-stage kidney disease (ESKD) and acute kidney injury (AKI) later in life. Design and method: Two cohort analyses were performed, firstly evaluating the link between adolescent BMI and CKD, ESKD and AKI throughout life, secondly assessing the link between BMI change from adolescence to midlife, and the risk of CKD, ESKD and AKI thereafter. Data from the Swedish Conscription Register, the Northern Sweden Health and Disease Study, the Swedish National Patient Register and the Cause of Death Register were included. Patients were stratified into quintiles of BMI in adolescence and BMI change until midlife. Data were analysed using Cox proportional hazards model. Results: 1 324 831 subjects met the inclusion criteria for BMI evaluation in late adolescence. The mean age at conscription was 18.3±0.8 years and the average BMI was 21.6±2.6 kg/m2. 5593 subjects developed CKD, 2358 developed ESKD and 8029 developed AKI. In the adjusted analyses, an increased risk of developing CKD and ESKD was seen from the fourth BMI quintile (HR 1.25, 95% CI 1.15-1.36 for BMI 21.9-23.6 kg/m2; HR 2.13, 95% CI 1.97-2.31 for BMI >23.6 kg/m2, for CKD), whereas the risk of AKI was increased already from the third BMI quintile (HR 1.15, 95%CI 1.15-1.24 for BMI 20.7-21.9 kg/m2). 32 221 subjects in a regional cohort had an additional BMI evaluation at mean age 42.1±8.6 years. The mean change in BMI between assessments was 4.8±3.2 kg/m2. We found that BMI increase of >7 kg/m2 from late adolescence to mid-life was associated with higher risk of CKD (HR 2.78, 95%CI 1.45-5.30) and AKI (3.49, 2.23-5.47) in non-adjusted analyses; only AKI persisted after adjustment (HR 2.60, 95%CI 1.58-4.28). Conclusions: To conclude, BMI in late adolescence is associated with CKD and ESKD, with increased risk from BMI levels >21.9 kg/m2. BMI increase during adulthood was only associated with an increased risk of AKI after covariate-adjustment, suggesting that adolescence is a critical period for the association between BMI and future kidney disease.