Body mass index and serum uric acid level: Individual and combined effects on blood pressure in middle-aged and older individuals in China

Few studies on the individual and combined analysis between serum uric acid (SUA) and body mass index (BMI) and blood pressure (BP) were conducted in individuals aged ≥45 years. We aimed to assess the extent to which BMI and SUA and their interaction affect BP in Chinese middle-aged and older adults. Data were selected from the China Health and Retirement Longitudinal Study (CHARLS). A total of 5888 individuals aged 45 to 96 was included. Differences between BMI, or between categories of blood pressure were evaluated by t test or chi-square test. The trend of related variables according to four BMI categories was also tested using contrast analysis. The adjusted associations between various characteristics and BP status were first compared using linear regression models, as appropriate. Then, general linear models adjusting for related potential confounders were used to examine the synergistic effect of SUA and BMI level on BP for middle-aged and elderly individuals in China. Age-adjusted partial Pearson correlation coefficient showed that BMI was significantly and positively correlated with BP both in male and female, SUA positively correlated with both systolic blood pressure (SBP) and diastolic blood pressure (DBP) in males with BMI <24.0 kg/m(2) and females with BMI <24.0 kg/m(2). However, SUA level significantly and positively correlated with DBP, but not with SBP, in females with BMI ≥24.0 kg/m(2). Multiple linear regression analysis showed that BMI was independently associated with BP both in male and female, SUA significantly and positively associated with SBP in both males and females with BMI <24.0 kg/m(2), However, SUA level positively correlated with DBP in females with BMI <24.0 kg/m(2), but not with males with BMI <24.0 kg/m(2), independent of other confounding factors. A general linear model analysis adjusted for confounding factors did not reveal interaction between BMI, SUA levels and SBP (β=-1.404, P = .686 in males; β=-2.583, P = .575 in females) and DBP (β=-2.544, P = .263 in males; β=-2.619, P = .622 in females). No interaction between BMI, SUA levels, and BP was observed in either males or females; However, BMI was independently associated with BP both in male and female, SUA independently associated with SBP both in males and females with BMI <24.0 kg/m(2), and SUA independently associated with DBP in females with BMI ≥24.0 kg/m(2).