Association of hemoglobin levels with metabolic syndrome and its components in older korean males: A nationwide population-based cross-sectional study

Metabolic syndrome (MetS) is a cluster of metabolic abnormalities associated with an increased risk of cardiovascular disease, type 2 diabetes mellitus, and mortality. Hemoglobin levels have been suggested to be associated with metabolic disorders and cardiometabolic risk factors; however, evidence regarding their relationship with MetS remains inconsistent, particularly in older populations. This study aimed to investigate the association between hemoglobin levels, MetS, and its components in older Korean males. This study analyzed data from the sixth Korea National Health and Nutrition Examination Survey (2013-2015). A total of 1680 men aged ≥ 60 years with normal hemoglobin levels (13-17 g/dL) were included, after excluding participants with cancer, chronic kidney disease, insufficient fasting time, or missing data. Participants were categorized into tertiles according to their hemoglobin levels. MetS was defined according to the modified National Cholesterol Education Program Adult Treatment Panel III criteria with Korean-specific waist circumference cutoffs, as the presence of at least 3 of the following components: abdominal obesity, elevated blood pressure, high fasting plasma glucose, high triglyceride levels, and low high-density lipoprotein cholesterol. Weighted logistic regression analyses were performed to evaluate the associations between hemoglobin tertiles and MetS and its components. The prevalence of MetS increased across hemoglobin tertiles (33.8%, 38.3%, and 48.8%, respectively). Participants in the highest tertile had significantly higher odds of having MetS (adjusted odds ratio [OR], 1.78; 95% confidence interval [CI], 1.28-2.47). Higher hemoglobin levels were also associated with abdominal obesity (OR, 2.03; 95% CI, 1.39-2.97), high fasting plasma glucose (OR, 1.71; 95% CI, 1.22-2.41), and high triglyceride levels (OR, 2.30; 95% CI, 1.64-3.22), but were not significantly associated with elevated blood pressure or low high-density lipoprotein cholesterol. Higher hemoglobin levels were significantly associated with an increased prevalence of MetS and several of its components in older Korean males. These findings suggest that hemoglobin levels may serve as a simple and accessible marker for identifying older adults at increased metabolic risk.