Association between White Blood Cell Counts within Normal Range and Hemoglobin A1c in a Korean Population

BACKGROUND: We examined whether white blood cell (WBC) count levels within normal range, could be associated with hemoglobin A1c (HbA1c) levels. METHODS: Among the 11,472 people (≥19 years of age) who participated in the 2011 to 2012 Korea National Health and Nutrition Examination, subjects with chronic disease or illness, including 807 patients with diabetes currently taking anti-diabetic medications and/or 1,149 subjects with WBC levels <4,000 or >10,000/µL were excluded. RESULTS: Overall, adjusted HbA1c levels increased across the WBC quartiles (5.55%±0.01%, 5.58%±0.01%, 5.60%±0.01%, and 5.65%±0.01%, P<0.001) after adjusting for confounding factors, such as age, gender, fasting plasma glucose, college graduation, smoking history, waist circumference, presence of hypertension, serum total cholesterol, serum triglyceride, and presence of anemia. The adjusted proportions (%) of HbA1c levels of ≥5.7%, ≥6.1%, and ≥6.5% showed significant increases across WBC quartiles (P<0.001, P=0.002, and P=0.022, respectively). Logistic regression analyses of WBC quartiles for the risk of HbA1c levels of ≥5.7%, ≥6.1%, and ≥6.5%, using the variables above as covariates, showed that the odds ratios of the fourth quartile of WBCs were 1.59 (95% confidence interval [CI], 1.35 to 1.89; P<0.001), 1.78 (95% CI, 1.31 to 2.42; P<0.001), and 2.03 (95% CI, 1.13 to 3.64; P=0.018), using the first quartile of WBCs as the reference. CONCLUSION: HbA1c levels were positively associated with WBC levels within normal range in a general adult population.