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

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.