Change in Body Mass Index and Attributable Risk of New-Onset Hypertension Among Obese Living Kidney Donors.

ABSTRACT

OBJECTIVE: To examine whether body mass index (BMI) changes modify the association between kidney donation and incident hypertension. BACKGROUND: Obesity increases hypertension risk in both general and living kidney donor (LKD) populations. Donation-attributable risk in the context of obesity, and whether weight change modifies that risk, is unknown. METHODS: Nested case-control study among 1558 adult LKDs (1976-2020) with obesity (median follow-up 3.6 years; interquartile range 2.0-9.4) and 3783 adults with obesity in the Coronary Artery Risk Development in Young Adults (CARDIA) and Atherosclerosis Risk in Communities (ARIC) studies (9.2 y; interquartile range 5.3-15.8). Hypertension incidence was compared by donor status using conditional logistic regression, with BMI change investigated for effect modification. RESULTS: Overall, LKDs and nondonors had similar hypertension incidence [incidence rate ratio (IRR) 1.16, 95% confidence interval (95% CI) 0.94-1.43, P =0.16], even after adjusting for BMI change (IRR 1.25, 95% CI 0.99-1.58, P =0.05). Although LKDs and nondonors who lost >5% BMI had comparable hypertension incidence (IRR 0.78, 95% CI 0.46-1.34, P =0.36), there was a significant interaction between donor and >5% BMI gain (multiplicative interaction IRR 1.62, 95% CI 1.15-2.29, P =0.006; relative excess risk due to interaction 0.90, 95% CI 0.24-1.56, P =0.007), such that LKDs who gained weight had higher hypertension incidence than similar nondonors (IRR 1.83, 95% CI 1.32-2.53, P <0.001). CONCLUSIONS: Overall, LKDs and nondonors with obesity had similar hypertension incidence. Weight stability and loss were associated with similar hypertension incidence by donor status. However, LKDs who gained >5% saw increased hypertension incidence versus similar nondonors, providing support for counseling potential LKDs with obesity on weight management postdonation.