Pre‐Transplant Obesity and Post‐Transplant Hypertension: Time‐Dependent Effect of Kidney Transplantation

Abstract

Background and Aims Obesity is associated with poor clinical outcomes including cardiovascular (CV) diseases, but it becomes protective for mortality in end‐stage kidney disease population as the so‐called reverse epidemiology. After successful kidney transplant (KT), association between obesity and transplant outcomes is conflicting. Hypertension (HTN) is one of the leading causes of CV morbidities and mortality in kidney transplant recipients (KTR). We aim to examine this association between pre‐KT obesity and post‐KT HTN over several post‐KT periods. Method This is a single center retrospective cohort including KTR who received KT between 2012 and 2015. The study population were divided into 3 groups: normal weight, overweight, and obesity based on pre‐KT body mass index (BMI) of <25, 25 ‐ <30, and ≥30 kg/m2, respectively. Association of the BMI categories with post‐KT systolic and diastolic HTN defined as SBP ≥130 and DBP ≥80 mmHg, respectively was examined by multivariable Cox proportional hazard regression analysis with a time‐dependent effect at 4, 12, 24, 36, and 48 weeks post‐KT. Results Of 105 patients, mean age±SD was 54±12 and 61% was female. Patients with normal weight, overweight, and obesity were account for 32%, 31%, and 36%, respectively and their corresponding mean BMI were 21.44±2.37, 27.32±1.38, and 34.27±3.53 kg/m2. There was no statistically significant difference in the risk of developing SHTN and DHTN at 4, 12, 24, and 36 weeks post‐KT. However, at 48‐week post‐KT, only obese, but not overweight had significant higher the risk for SHTN (HRobese 2.29, p 0.017, 95% CI 1.160, 4.51; HRoverweight 1.24, p 0.571, 95% CI 0.60, 2.56) after adjusted for age, gender, type of KT, and immunosuppression. For obesity‐DHTN association, both obese and overweight groups had 308% and 154% significantly greater risk for DHTN in multivariable analysis, respectively (HRobese 4.08, p 0.002, 95% CI 1.66, 10.00 and HRoverweight 2.54, p 0.046, 95% CI 1.02, 6.35). Conclusion Obesity at the time of KT was associated with increased risk of SHTN at the long‐term, but not short‐term post‐KT; whereas overweight increased risk of both SHTN and DHTN at the long‐term‐post‐KT. Immunologic or non‐immunologic during short‐term post‐KT may contribute to these associations and further studies are required to elucidate the mechanism.