Underweight rather than overweight is associated with higher prevalence of hypertension: BP vs BMI in haemodialysis population

Background. Recent surveys have reported a higher prevalence of hypertension and obesity in the haemodialysis population, suggesting a possible link between these two parameters. Alternatively, malnutrition through proinflammatory and antiendothelial mechanisms may contribute to hypertension in malnourished, underweight patients on haemodialysis, whereas the converse may be true in overweight patients. Methods. The relationship between blood pressure (BP) and body mass index (BMI) was examined in 1010 patients on chronic haemodialysis using univariate and multivariate analyses. Results. Based on a systolic BP of >150 mmHg, 38% were hypertensive in the post-dialysis period. A similar figure for a diastolic BP of >90 mmHg was 21%. Unlike in the general population, there was no positive correlation between BP and BMI in simple regression analysis (r = −0.13, P = 0.0005). The percentage of patients with systolic hypertension was higher among the underweight (BMI 27.5) and were 35, 29 and 20%, respectively. Furthermore, a negative correlation, albeit weak, existed between systolic BP and markers of nutrition such as serum prealbumin (r = −0.10, P = 0.03) and serum creatinine (r = −0.12, P = 0.008), suggesting a plausible link between impaired nutrition and elevated BP. In multiple regression analysis, the lack of a positive correlation between BP and BMI persisted (r = −0.16, P = 0.0007) in spite of adjusting for case-mix characteristics and parameters related to BP and nutrition. Conclusions. We demonstrate for the first time that, unlike the general population, no positive correlation exists between BP and increasing BMI in haemodialysis patients. Further analysis is necessary to verify our observation and to test the possibility of whether nutritional improvement would aid in the better control of hypertension in dialysis patients.