What does a daytime nap do for your health?
A daytime nap improves alertness, memory and concentration, especially if you take it before 13:00 and keep it between 20 and 40 minutes. Longer naps also work, but expect around fifteen minutes of grogginess before you truly reap the benefits.
A short nap of 5 to 15 minutes produces an almost immediate sharpening of the mind and greater alertness, but the effect lasts only 1 to 3 hours. A nap of 30 to 40 minutes sustains those benefits for longer: accuracy on attention and arithmetic tasks improves throughout the entire afternoon, and mood, vitality and self-control also benefit.
Those with more time available can opt for a 90-minute nap. This restores activity in the memory regions of the brain and improves the ability to absorb new information. The downside: immediately after waking from a longer nap you initially feel groggy. Athletes are advised to wait at least 1 hour after a nap of an hour or more before competing, even though objective performance measures are not significantly worse at that point.
Broad research confirms that afternoon naps deliver benefits across multiple aspects of cognitive functioning: alertness, memory and processing speed. The strongest effect is on alertness. The benefits apply across different age groups and nap durations.
Timing matters. A nap taken before 13:00 appears to provide the greatest cognitive benefit, although this difference was not statistically significant in the research. People who nap regularly also appear to gain more from napping than those who rarely do, although the latter finding has not yet been studied sufficiently.
This answer draws on two broad analyses covering more than sixty nap studies in total, supplemented by smaller studies on specific nap durations and timing. The evidence for short-term cognitive benefits is reasonably consistent. The smaller studies, some with 15 participants or fewer, should be interpreted with caution. These sources say nothing about long-term effects on health, night-time sleep quality or outcomes other than cognition.
Is a daytime power nap healthy or not?
A power nap of less than 30 minutes taken early in the afternoon provides a modest but measurable boost to alertness and concentration, without the health risks associated with longer naps. For most people, such a short nap does not disrupt night-time sleep either.
Does walking outside during the day help me sleep better at night?
A daily walk of around half an hour outside helps improve your sleep, as shown by a randomised study. The surroundings matter little, but air pollution can dampen the effect.
How harmful is irregular sleep or shift work, and what can you do about it?
Shift work is demonstrably harmful to sleep, alertness and metabolism. The best approach combines a well-designed schedule with forward rotation, strategic use of light, melatonin and, where appropriate, cognitive behavioural therapy.
Does the timing of your meals affect how well you sleep?
Eating late is associated with taking longer to fall asleep and poorer sleep quality, although cause and effect have not always been proven. Try to have your last meal at least two to three hours before bedtime and limit evening snacks, especially if you already have difficulty sleeping.
Is it a problem that I often wake up during the night?
Regularly waking during the night affects your mood, concentration and, over time, your health. If it is a structural problem, it is worth doing something about it, starting with a proven behavioural approach to sleep.
Why am I wide awake in the evening when I feel tired during the day?
Your biological clock and your chronotype determine when your body wants to be awake. When that clock does not align with your daily schedule, you feel tired during the day and wide awake in the evening. Light exposure at the right time and a consistent sleep schedule are the most well-supported ways to correct this.