Association between Insomnia Symptoms and Hemoglobin A(1c) 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.