Does late morning waking-up affect sleep during the following night in patients with primary insomnia?

Night-to-night variability in sleep duration and schedule is common in patients with insomnia. Among the various sleep variables, waking-up time is focused upon as the important factor for cognitive behavioural therapy for insomnia. This study examined the effect of a single late waking-up episode on sleep in the immediate following night in patients with chronic insomnia, using data from a placebo group (380 patients) of a double-blind placebo-controlled study. Patients tended to wake up later and have a longer total sleep time on weekends than weekdays. It was suggested that patients who woke up late one morning (>= 60 min later than the individual's regular waking-up time) extended their sleep onset latency by 4.3min in the immediate following night. The effects of late waking-up on total sleep time and bedtime were not clear. The importance of keeping regular waking-up time is highlighted for better sleep in patients with insomnia.