Sex Differences in the Nonlinear Association Between BMI and LDL Cholesterol in Middle-Aged and Older Adults: Results from two Nationally Representative Surveys of China

Abstract

\n Background: The association between body mass index (BMI) and low-density lipoprotein cholesterol (LDL-C) in middle-aged and older man and women was understudied. We aimed to explore whether there were sex differences in this relationship in a large sample of Chinese adults.Methods: Participants in the China Health and Retirement Longitudinal Study (CHARLS, 2011-2012) (n=7485) and the China Health and Nutrition Survey (CHNS, 2009) (n=4788) were cross-sectionally investigated. Generalized additive models with a smooth function for BMI and a smooth-factor interaction for BMI with sex were performed and stratified by age and metabolic syndrome. Segment linear splines regressions were fitted to calculate the slopes with the different breakpoints.Results: Among the 12273 participants aged 45 to 75 years, 5780 (47.1%) were males. The nonlinear relationship between BMI and LDL-C was observed in females and males (P interaction <0.001). The slopes of the BMI and LDL-C association changed (P <0.001) at BMI 22.5 kg/m2 in females and 27.5 kg/m2 in males. Below these BMI breakpoints, LDL-C increased 2.14 (95% CI: 1.42 to 2.86) and 1.77 (95% CI: 1.43 to 2.11) mg/dL per kg/m2, respectively. In females, there was a plateau at BMI values of 22.5-27.5 kg/m2, and then gradually increased after a BMI of 27.5 kg/m2. However, LDL-C declined -1.84 (95% CI: -3.01 to -0.66) mg/dL per kg/m2 above BMI of 27.5 kg/m2 in males. The pattern of sex and BMI-LDL-C association was similar in all age groups but modified by the number of metabolic syndrome criteria.Conclusions: The BMI and LDL-C relationship was inverted U-shaped in males and approximately linear in females.