Sleep, fatigue, recovery, and depression after change in work time control: a one-year follow-up study.

OBJECTIVE: We examined how change in work time control was associated with sleep and health 1 year later. METHODS: Work time control, sleep, fatigue, recovery, and depression were assessed at baseline (T1) and at follow-up (T2) for 2382 daytime workers. The change in work time control from T1 to T2 was classified into four groups: low to low, low to high, high to low, and high to high. RESULTS: A repeated-measures analysis of covariance showed significant decreases in the frequency of insomnia symptoms and depressive symptoms from T1 to T2 for the low to high group, which were similar to the high to high group. Significantly lower fatigue was found for these two groups at T2. CONCLUSION: An increase in work time control, in addition to its stable high level, may produce beneficial effects upon sleep and health.