The effects of sleep deprivation: what short nights do to attention, memory, mood and driving

In this article you will read what sleep deprivation does to attention, memory, mood and driving, how much of it comes back with catch-up sleep, and when sleeping badly is worth an appointment with your GP. That matters, because sleep deprivation has effects that stack up faster than the feeling of sleepiness does: in the best measured experiment, scored sleepiness levelled off while performance kept falling.⁠¹ The BioProfile sleep scan gives you an indication of where you stand today in the area of sleep, as one of the 11 health areas the full scan assesses. This is not a diagnosis. It is insight, to see where you stand today and to help you make better choices in your food and lifestyle. What this scan does not do: point out a cause or make a diagnosis. Only a doctor can do that.

How short is short, and how common it is

Most adults sleep 7 to 9 hours a night, and 7 or 8 hours at an older age.⁠³ In pooled data from 1.1 million people in the Netherlands, the United Kingdom and the United States, one in four slept less than the guideline for that age, and among teenagers 51.5% slept less than the recommended 8 to 10 hours.⁠⁴ In the Netherlands in 2024, just over one in four people aged 12 and older had trouble falling asleep or staying asleep, or woke too early, and that share rose in every age group between 2017 and 2024.⁠⁵ Of 3,695 Dutch adults followed for 20 years, 40% changed sleep pattern, and 43% of those became short sleepers.⁠⁶

Chronic sleep deprivation is usually a shift over years and rarely one bad week.

Effects of sleep deprivation on your attention

48 healthy adults were randomly assigned to 4, 6 or 8 hours in bed a night, 14 nights in a row. The 4 hour and the 6 hour groups built up dose-dependent deficits on every cognitive task, and 6 hours or less across those nights produced deficits that matched up to 2 nights of no sleep at all, while self-rated sleepiness rose only slightly and the 6 hour group did not separate from the 4 hour group.⁠¹

After a week of 6 hours, 6 hours feels normal, while the bill keeps running.

In a meta-analysis of 70 papers and 147 cognitive tests, all covering a single period of less than 48 hours without sleep, the largest effect was on lapses in simple attention (g = -0.776, 95% CI -0.96 to -0.60) and the smallest on the accuracy of reasoning (g = -0.125); only time awake predicted how much the outcomes differed between studies.⁠⁷

Attention goes before thinking: what falls away is seeing in time what happens right in front of you.

Mental effects of sleep deprivation: memory and mood

28 participants were randomly assigned either to a night without sleep, about 35 hours awake at the moment of the learning task, or to a normal night. On a recognition test 2 days later, with two nights of catch-up sleep in between, the group that had learned after the night awake scored 19% lower (d-prime 2.17 versus 2.58, P = 0.031), with lower activity in both posterior hippocampal regions during learning.⁠⁸

What you take in on the day after a night awake is stored less well.

Across 154 experiments, with 1,338 effect sizes and 5,717 participants aged 7 to 79, a whole night awake, shortened nights and nights broken by waking all gave lower positive mood (standardised mean differences of -0.27 to -1.14) and more anxiety symptoms (0.57 to 0.63).⁠²

Less pleasure in things and more worrying, with broken nights counting just as heavily as short ones. If you sleep long enough and still wake up exhausted, that is where it starts: what a sleep test measures about that is in why you wake up tired.

What lack of sleep does behind the wheel

Among 6,845 drivers in a representative sample of American crashes from 2005 to 2007, the chance of being held at fault, compared with drivers who had slept 7 to 9 hours in the past 24 hours, was 1.3 times as high after 6 hours, 1.9 times after 5 hours, 2.9 times after 4 hours and 15.1 times after less than 4 hours.⁠⁹

The step from 5 hours to less than 4 is where the line gets steep: after a night like that, you let someone else drive.

What catch-up sleep gives back

13 participants were followed for 21 days in a row: 4 days of normal life as a baseline, 10 days in which sleep was cut by 30% of their own sleep need, and 7 days of catch-up sleep. After those 7 days only the average reaction time on the Stroop task was back at baseline; accuracy on the task, the EEG measures, the event-related potentials and the actigraphy patterns all stayed below it.⁠¹⁰

A week of longer nights has you feeling better before the measurements follow: a long weekend makes a start on the bill, rather than settling it.

When to see your GP

Sleeping badly means trouble falling asleep, lying awake for a long time, or waking up too often or too early, with tiredness and less concentration during the day. Make an appointment with your GP if you want to talk about your sleep problems.⁠³ Worth checking first: even 1 or 2 cups of coffee make the quality of your sleep worse, and nicotine, alcohol and cannabis are named as causes too.⁠³

In summary

Short sleep is common and usually builds up over years.⁠^4,6 Two weeks of 6 hours a night leaves deficits comparable to up to 2 nights fully awake, while the feeling of sleepiness lets go of those deficits at a certain point.⁠¹ Simple attention takes the biggest hit, that day’s memory is weaker two days later, mood drops while anxiety symptoms rise, and the chance of being held at fault behind the wheel goes up as the night gets shorter.⁠^7,8,2,9 A week of catch-up sleep gives part of that back.⁠¹⁰ A sleep scan gives you your own starting value on all of it.