Key points
- A moderate dose of caffeine disrupts sleep even when taken 6 hours before bed[3].
- Alcohol helps you fall asleep but disrupts the second half of the night[4].
- In one study, reading on a light-emitting screen in the evening delayed sleep and the body clock[5].
- On its own, sleep hygiene is not a treatment for chronic insomnia[1][2].
Coffee and other sources of caffeine
In a study carried out at home, a moderate dose of caffeine (400 mg, the equivalent of several cups of coffee) disrupted sleep whether it was taken at bedtime, 3 hours or even 6 hours before. The authors conclude that it is best to avoid a large intake of caffeine for at least 6 hours before bed[3].
Coffee isn't the only source: tea, cola, energy drinks and chocolate contain it too. Sensitivity varies a great deal from one person to another, so the simplest approach is to observe how it affects you.
Before and after 2 pm
The ReSomnia diary records your cups of coffee, tea or cola before and after 2 pm. After a few weeks, it shows whether your nights are worse after a late coffee.
Alcohol
A review of all the studies carried out in healthy volunteers shows that, at all doses, alcohol shortens the time it takes to fall asleep and consolidates the first half of the night, but disrupts the second[4]. That's the trap of the “nightcap”: you fall asleep faster, but you wake more often towards the end of the night.
Screens and evening light
In a study comparing reading on a light-emitting e-reader with reading a printed book before bed, reading on a screen delayed sleep, reduced evening sleepiness and the secretion of melatonin (the sleep hormone), shifted the body clock and lowered alertness the next morning[5].
In practice: soft lighting in the evening, and a printed book rather than a screen when you are winding down.
Regular hours
Getting up at the same time every day, weekends included, helps your body clock settle. In CBT-I, this fixed wake-up time is the anchor of sleep restriction. Long or late naps, on the other hand, reduce your drive to sleep in the evening.
Why it isn't enough
The American Academy of Sleep Medicine guideline advises against using sleep hygiene as the only treatment for chronic insomnia (a conditional recommendation)[1]. And within CBT-I, the analyses comparing the components find no specific effect from it[2].
If you've already tried everything
Many people with insomnia already follow this advice without results. This is not a personal failure: chronic insomnia is kept going mainly by time spent awake in bed and worry about sleep. That is where CBT-I comes in, with sleep restriction and stimulus control.