Study design and participants

This cross-sectional investigation analyzed baseline data collected for a prospective cohort study. Briefly, a total of 2560 asymptomatic participants with no history of CV and cerebrovascular disease, neurological abnormalities, or malignancy took part in baseline health examinations in the Seoul area between April 2010 and November 2012 [11]. All participants were stratified into four groups based on Hb quartiles, as follows: ≤ 12.8 g/dL (group I), 12.9–13.6 g/dL (group II), 13.7–14.5 g/dL (group III), and ≥ 14.6 g/dL (group IV). Hypertension was defined as a systolic blood pressure (BP) of ≥ 140 mmHg and/or a diastolic BP of ≥ 90 mmHg, or use of anti-hypertensive medications. Hyperlipidemia was defined as a total cholesterol level of ≥ 240 mg/dL or treatment with lipid-lowering agents. Diabetes was defined as a fasting glucose level of ≥ 126 mg/dL or use of anti-diabetic medications. MetS was defined as present when three or more of the following criteria were satisfied: (a) systolic B p ≥ 130 mmHg or diastolic B p ≥ 85 mmHg, or use of anti-hypertensive medications; (b) abdominal obesity based on a waist circumference of ≥ 90 cm in men or ≥ 80 cm in women; (c) high-density lipoprotein cholesterol (HDL-C) level of < 40 mg/dL in men or < 50 mg/dL in women; (d) fasting triglycerides ≥ 150 mg/dL; and (e) fasting glucose ≥ 100 mg/dL or use of anti-diabetic medications [7].