Starting point
People who sleep badly sometimes try going to bed earlier, and then lie awake. This impulse starts at the other end of the night, at the time you get up. You cannot force the moment of falling asleep. You can set the alarm.
Why regularity makes sense
Two things govern sleep: sleep pressure, which builds up during time awake, and the body clock, which sets a daily rhythm for the body. A fixed getting-up time gives both the same starting point every day. Someone who sleeps in for a long time on Sunday is often not yet tired in the evening, and finds it harder to get into the new week.
The German guideline on insomnia lists the sentence “Get up at the same time every morning” as one of the rules of stimulus control [1]. Stimulus control is part of cognitive behavioural therapy for insomnia (CBT-I). According to the guideline, this therapy should be recommended to all people with insomnia as the first treatment option, at the highest strength of recommendation [1]. In the therapy, time in bed is also shortened for a while, and daytime sleep is avoided. That increases sleep pressure and steadies the sleep-wake rhythm [1].
Results
In two small laboratory studies with 11 and 12 young, healthy men, sleep was deliberately shortened. After six nights with only four hours in bed, glucose tolerance was lower than after a recovery period, so the body processed sugar less well. At the same time, the stress hormone cortisol was raised in the evening [2]. In the second study, after two days of shortened sleep, the satiating hormone leptin fell, the appetite-stimulating hormone ghrelin rose, and hunger and appetite increased, especially for high-calorie, carbohydrate-rich foods. Calorie intake was controlled [3]. Both studies point, under extreme conditions, to a possible mechanism. They do not answer what happens over years in everyday life.
There are also observational data. A meta-analysis of 10 studies with more than 100,000 people found that those who slept 5 to 6 hours or less, or who had trouble falling or staying asleep, developed type 2 diabetes more often. Very long sleep of more than 8 to 9 hours was also associated with a higher risk of diabetes [4]. A single large observational study from the United Kingdom, with about 61,000 people, measured sleep with movement sensors. People who slept more regularly had a lower risk of death, and regularity predicted this risk better than sleep duration [5]. Studies of this kind show associations. They do not prove that sleep is the cause.
Evidence moderate
CBT-I is well supported in insomnia. The guideline bases its recommendation on meta-analyses with the highest level of evidence [1]. The fixed getting-up time is one component among several there. Whether it helps people without a sleep disorder on its own cannot be inferred from the guideline. On metabolism there are small short-term studies and observational data [2, 3, 4, 5]. None of these studies has examined whether a fixed getting-up time lowers the risk of type 2 diabetes.
How to put it into practice
- Choose a fixed getting-up time for all seven days: pick a time you can also keep at the weekend, and set the alarm accordingly [1].
- Go to bed when you are sleepy, not by the clock. If you are still lying awake after 15 minutes, get up, do something pleasant, and go back to bed only when you are sleepy [1].
- After a bad night, still get up at the usual time and do not lie down during the day [1]. Good nights can follow bad ones again [1]. The method can make you tired for a while; if you feel sleepy, do not drive [1].
- Keep the evening calm. The rules in the guideline include, among other things: no drinks containing caffeine after lunch, no alcohol as a sleep aid, no heavy meals in the evening, and a personal ritual for falling asleep [1]. In insomnia, however, such rules on their own are not enough as treatment [1].
Type 2 diabetes and shift work
Someone living with type 2 diabetes can use the same steps and mention their own sleep at the next appointment, even without symptoms. If a new rhythm shifts the times for meals or medicines, discuss that with your treatment team. For people on shift work, a fixed getting-up time often does not fit, and an individual solution is needed. According to the guideline, there are indications that CBT-I could also work for sleep disorders linked to shift work [1].
When medical advice is useful
Have your sleep checked by a doctor if you snore loudly and irregularly, if someone notices breathing pauses at night, or if you nod off unintentionally during the day. These can be signs of sleep apnoea. The same applies if trouble falling or staying asleep continues for weeks and burdens daily life [1].
If you have epilepsy or bipolar disorder, are pregnant, or your work carries responsibility for others’ safety, discuss changes to your sleep pattern with a doctor first.