Sex-related associations among anemia, body mass index, and kidney function in Koreans: A cross-sectional study with propensity analysis

The association between anemia and body mass index (BMI) in Koreans, considering kidney function, has not been clarified. Thus, we aimed to examine the association between anemia and BMI among Korean adults aged ≥19 years. This retrospective cross-sectional study evaluated male and female Korean adults aged ≥19 years who participated in the 5th, 6th, and 7th Korean National Health and Nutrition Examination Surveys (KNHANES) conducted between 2010 and 2017 were used. The participants were classified as underweight, normal weight, and overweight according to their BMI. Anemia was defined as hemoglobin levels of <13 g/dL for men and <12 g/dL for women according to the World Health Organization standards. Kidney function was evaluated according to the estimated glomerular filtration rate (eGFR), with abnormal kidney function in men defined as eGFR <60 mL/min/1.73 m(2). Clinicodemographic variables were analyzed using logistic regression adjusted for weight. After propensity score matching (PSM), 6596 study participants were divided into 2 groups of 3298 participants each. Additionally, subgroup analysis by sex and kidney function was performed. On PSM, similar distribution patterns were obtained between the anemia and non-anemia groups; significant differences in BMI; kidney function; level of hemoglobin, hematocrit, and serum creatinine; iron intake; and eGFR were also observed between these groups. Anemia and BMI showed a significant association in both crude and adjusted logistic regression models. In model 2, which was adjusted for age, sex, education level, household income, alcohol consumption, smoking status, and exercise period, underweight men with abnormal kidney function showed a significantly higher risk of anemia than did normal weight men (odds ratio [OR]: 3.27; 95% confidence interval [CI]: 1.25–8.57; P = .016). Meanwhile, overweight men showed a significantly lower risk of anemia than did normal weight men (OR: 0.48; 95% CI: 0.33–0.70, P < .001). Anemia is associated with BMI according to sex. Compared with normal weight men, underweight men with abnormal kidney function had a significantly higher prevalence of anemia after adjusting for kidney function and sex, thus highlighting their need for careful management for anemia.