Association between Insomnia Symptoms and Hemoglobin A1c Level in Japanese Men

Background The evidence for an association between insomnia symptoms and blood hemoglobin A 1c (HbA 1c ) level has been limited and inconclusive. The aim of this study was to assess whether each symptom of initial, middle, and terminal insomnia influences HbA 1c level in Japanese men. Methods This cross-sectional study examined 1,022 male workers aged 22–69 years with no history of diabetes at a Japanese company's annual health check-up in April 2010. High HbA 1c was defined as a blood level of HbA 1c ≥6.0%. Three types of insomnia symptoms (i.e., difficulty in initiating sleep, difficulty in maintaining sleep, and early morning awakening) from the previous month were assessed by 3 responses (i.e., lasting more than 2 weeks, sometimes, and seldom or never [reference group]). Results The overall prevalence of high HbA 1c was 5.2%. High HbA 1c was positively and linearly associated with both difficulty in maintaining sleep (P for trend  = .002) and early morning awakening (P for trend  = .007). More specifically, after adjusting for potential confounding factors, high HbA 1c was significantly associated with difficulty in maintaining sleep lasting more than 2 weeks (adjusted odds ratio, 6.79 [95% confidence interval, 1.86–24.85]) or sometimes (2.33 [1.19–4.55]). High HbA 1c was also significantly associated with early morning awakening lasting more than 2 weeks (3.96 [1.24–12.59]). Conclusion Insomnia symptoms, particularly difficulty in maintaining sleep and early morning awakening, were found to have a close association with high HbA 1c in a dose-response relationship.