Association between long-term alcohol consumption and insomnia symptoms in civil servants: Aichi Workers' Cohort Study.

Objectives: The influence of habitual alcohol consumption on insomnia symptoms in healthy workers remains unclear. In this study, we evaluated the association between habitual alcohol consumption among civil servants and insomnia symptoms such as difficulty falling asleep, difficulty staying asleep, and tiredness after sleep, using longitudinal data. Methods: We enrolled civil servants in a prospective cohort study who completed questionnaires at baseline. Of those, 2861 participants were revaluated in a 5-year follow-up survey. Insomnia symptoms during the past month were assessed using self-reporting. Alcohol drinking habits were assessed by querying the frequency of drinking alcohol as well as the amount of alcohol usually consumed per one occasion. Results: Drinking alcohol every day was less likely to have difficulty falling asleep (odds ratio, 0.42 95% confidence interval, 0.20-0.89), and drinking alcohol 3 or more days a week was associated with difficulty staying asleep (odds ratio, 1.48; 95% confidence interval, 1.16-1.90). Conclusions: Drinking alcohol every day may produce subjective improvement in sleep onset. However, drinking alcohol 3 or more days a week may increase arousal during sleep, which contributes to reduced sleep quality. These results suggest the possibility that long-term daily habitual drinking may reinforce a sense of improvement in subjective sleep onset but may possibly induce sleep disturbance.