To investigate the association between white blood-cell (WBC) count and the development of diabetes, independent of cigarette smoking.

We examined 2953 Japanese men who were office workers and between 35 and 59 years of age and who did not have impaired fasting glucose (IFG) (a fasting glucose concentration of 6.1–6.9 mmol/l), Type II (non-insulin-dependent) diabetes mellitus (a fasting glucose concentration of ≥ 7.0 mmol/l or more or receipt of hypoglycaemic medication), medication for hypertension, and a history of cardiovascular disease. Fasting glucose concentrations were measured at annual health examinations from May 1994 through May 2000.

After controlling for potential predictors of diabetes, the relative risk for IFG or Type II diabetes mellitus compared with a WBC count of less than 5.3 · 10⁹ cells/l was 1.2 (95 %-CI, 0.6–2.3), 1.6 (CI, 0.8–3.1), and 2.5 (CI, 1.2–5.1) among non-smokers (p for trend = 0.009): and 1.0 (CI, 0.4–2.5), 2.3 (CI, 1.0–5.1), and 3.1 (CI, 1.4–7.1) among ex-smokers (p for trend = 0.001) with WBC counts of 5.3–6.1, 6.2–7.2, and 7.3 · 10⁹ cells/l or more, respectively. Among current smokers, the respective multivariate-adjusted relative risks for IFG or Type II diabetes mellitus were 1.1 (CI, 0.6–2.1), 1.4 (CI, 0.8–2.4), and 1.2 (CI, 0.7–2.1) (p for trend = 0.460).

Although the selection of a rigorously normoglycaemic cohort might have had an influence on these observations, higher WBC counts seem to predict the development of IFG or Type II diabetes mellitus, primarily in non-smokers. [Diabetologia (2002) 45: 42–48]