Inverse relationship between Body Mass Index (BMI) and Blood Pressure (BP) in patients on hemodialysis

BMI and BP may influence the mortality of patients on hemodialysis. In separate analysis, a high prevalence of hypertension (AJKD 28:737-40, 1996) and overweight (JASN 9:208A, 1998) were observed in our hemodialysis population. In general population, overweight is often associated with elevated BP. However, it is not known whether such a relationship exists in patients on hemodialysis. In this study, we analyzed the relationship between BP and BMI in 665 patients on chronic hemodialysis. BMI was calculated using the postdialysis weight. Mean BP was obtained by averaging the BP for an entire month. 89% of patients were Afro-American and the rest were Caucasian. Pre-and post-dialysis MAP were 110±14 (m+SD) and 102±13 mm Hg. Using a post-dialysis MAP of >100, 57% of patients were found to be hypertensive. Antihypertensive medications were prescribed in 48% of patients. The BMI for the population was 27±7. Overweight (OW, BMI>27.5) was found in 37% of patients, whereas underweight was noted in 12% (UW, BMI<20), with the remainder in the normal weight (NW) group. In simple regression analysis, MAP correlated negatively with BMI (r -0.22, p=0.004), which persisted across race and gender. A higher percent of UW patients compared to NW and OW patients were hypertensive and were receiving antihypertensive medications. In multiple regression analysis, the inverse relationship between BMI and MAP persisted after adjusting for age, duration on dialysis and Kt/V. Thus, unlike in general population, higher BMI is associated with lower BP in patients on hemodialysis. Proper nutrition and normal BMI may be important in maintaining normal BP in patients on hemodialysis.