WBC count predicts heart failure in diabetes and coronary artery disease patients: a retrospective cohort study

AIMS: White blood cell (WBC) count in healthy people is associated with the risk of coronary artery disease (CAD) and mortality. This study aimed to determine whether WBC count predicts heart failure (HF) requiring hospitalization as well as all‐cause death, acute myocardial infarction (AMI) and stroke in patients with Type 2 diabetes mellitus and established CAD. METHODS: We conducted this retrospective registry study that enrolled consecutive patients with Type 2 diabetes mellitus and CAD based on coronary arteriography records and medical charts at 70 teaching hospitals in Japan from 2005 to 2015. A total of 7608 participants (28.2% women, mean age 68 ± 10 years) were eligible. In the cohort, the median (interquartile range) and mean follow‐up durations were 39 (16.5–66.1 months) and 44.3 ± 32.7 months, respectively. The primary outcome was HF requiring hospitalization. The secondary outcomes were AMI, stroke, all‐cause death, 3‐point major adverse cardiovascular events (MACE) (AMI/stroke/death) and 4‐point MACE (AMI/stroke/death/HF requiring hospitalization). Outcomes were reported as cumulative incidences (proportion of patients experiencing an event) and incidence rates (events/100 person‐years). The primary and secondary outcomes were assessed using the Kaplan–Meier method and were compared using the log‐rank test stratified by the baseline WBC count. The association between the WBC count at baseline and each MACE was assessed using the Cox proportional hazard model and expressed as the hazard ratio (HR) and 95% confidence interval (CI) after adjusting for other well‐known risk factors for MACE. RESULTS: During the follow‐up, 880 patients were hospitalized owing to HF. The WBC Quartile 4 (≥7700 cells/μL) had significantly lower HF event‐free survival rate (log‐rank test, P < 0.001). The HRs for HF events requiring hospitalization with each WBC quartile compared with the lowest in the first WBC quartile were 1 for Quartile 1 (WBC < 5300 cells/μL), 1.20 (95% CI, 0.96–1.5; P = 0.1) for Quartile 2 (5300 ≤ WBC < 6400), 1.34 (95% CI, 1.08–1.67; P = 0.009) for Quartile 3 (6400 ≤ WBC < 7700) and 1.62 (95% CI, 1.31–2.00; P < 0.001) for Quartile 4 after adjusting for covariates. Similar findings were observed for the risk of AMI and death; however, no significant difference was found for stroke. WBC Quartile 4 patients had a significantly lower 3‐ or 4‐point MACE‐free survival rate (log‐rank test, P < 0.0001). CONCLUSIONS: A higher WBC count is a predictor of hospitalization for HF, all‐cause death and AMI but not for stroke in patients with concurrent Type 2 diabetes mellitus and established CAD.