Sleep-related risk of occupational injuries in Japanese small and medium-scale enterprises

A cross-sectional study evaluated the contribution of daily sleep habits to occupational injuries. A self-administered questionnaire solicited answers about sleep, symptoms of depression, occupational injury, demographics, presence of diseases and lifestyle factors from 2,903 workers between the ages of 16-83 (mean 45) yr in small and medium-scale enterprises. Eight sleep habits were queried and dichotomized: 1) less or more than 6 hr of daily sleep, 2) taking more or less than 30 min to fall asleep (Difficulty initiating sleep; DIS), 3) awakening during sleep more or less than 3 times/wk (Difficulty maintaining sleep; DMS), 4) early morning awakening more or less than 3 times/wk (EMA), 5) definitely/somewhat difficulty waking up or not, 6) sleeping very poorly/not so well at night or not, 7) definitely/somewhat insufficient nightly sleep or not, and 8) difficulty in breathing during sleep more than once/week or less. Occupational injury was assessed by asking subjects 'Have you ever been injured during your work, including minor scratches and cuts (Yes/No)?' Both sleep and injury were assessed over the previous one year period. One-third of workers answered that they had experienced injury. Workers with sleep features of DIS, sleeping poorly at night, insufficient sleep, and insomnia had a significantly higher prevalence for injury after adjusting for multiple confounders. The findings suggest that poor nocturnal sleep habits are associated with self-reported occupational injury.