Sleep helped people remember to do planned things, though the effect may be overstated.

The review

1. 01

   Who took part

   The studies covered 165,432 people aged 15 to 93 from 10 countries. They were healthy people, and some had sleep disorders.

2. 02

   What they did

   Ten studies were experiments. In them, people slept or stayed awake after learning what they had to do later, or were kept from sleeping. Ten other studies compared memory in people with different sleep habits or sleep disorders.

3. 03

   What happened

   Overall, people who slept remembered planned actions better than people who stayed awake or slept less. The effect was small to medium, and it shrank to a small one once the paper allowed for missing studies. Sleep did not clearly slow people's other tasks.

What the review found

1. HelpedProcrastination

   Across 24 studies, sleep helped people remember planned actions more than being awake or sleeping less did.

   Pooled analysis of 24 studies with 165,432 people · vs people who stayed awake or slept less · ⚠ signs that small negative studies went unpublished; the studies disagreed a lot; mixes trials with other kinds of study

2. No differenceFocus

   Across 6 studies, sleep did not make people slow their other task to watch for their plans.

   Pooled analysis of 6 studies · vs people who stayed awake · behaviour was recorded · ⚠ mixes trials with other kinds of study

3. HelpedProcrastination

   Across 3 studies, sleep helped people remember more when a cue was likely to bring the plan to mind.

   Pooled analysis of 3 studies · vs people who stayed awake on the same tasks · behaviour was recorded · ⚠ mixes trials with other kinds of study

4. No differenceProcrastination

   Across 7 studies of people aged 40 to 93, sleep made no clear difference to remembering.

   Pooled analysis of 7 studies · vs people who stayed awake · ⚠ mixes trials with other kinds of study

Source