If your mom is anything like ours, she's been telling you to go to bed since you were five. "It's past your bedtime!" "Just five more minutes!" It turns out she had good reason. Here's how much sleep adults actually need, what happens when you don't get it, and fifteen reasons to turn in a little earlier tonight.
How much sleep do adults need?
The American Academy of Sleep Medicine and the Sleep Research Society agree that adults should sleep 7 or more hours a night on a regular basis. Regularly sleeping less than that is linked with a long list of health problems, which is why "I'm fine on five hours" deserves a second look.
What does lack of sleep do to your body?
- It strains your heart. In a meta-analysis of 15 prospective studies, short sleepers had a 48% higher risk of developing or dying from coronary heart disease.
- It raises stroke risk. The same analysis found a 15% higher risk of stroke with short sleep.
- It disrupts blood sugar. Short and poor-quality sleep both predicted a higher risk of developing type 2 diabetes.
- It's linked with weight gain. Short sleep is associated with higher odds of obesity in both children and adults.
- It makes you hungrier. After two nights of short sleep, healthy young men had 18% less leptin, 28% more ghrelin and 24% more hunger, with the biggest cravings for calorie-dense, carb-heavy foods.
- It affects your brain's clean-up. One night without sleep increased beta-amyloid in parts of the brain, the protein that builds up in Alzheimer's disease.
- It makes you more emotionally reactive. Sleep-deprived volunteers showed a stronger amygdala response to negative images and weaker connection to the brain's regulating prefrontal cortex.
- It weakens your defenses. When volunteers were exposed to a cold virus, those sleeping under 6 hours were more than four times as likely to catch a cold as those sleeping over 7.
- It's tied to inflammation. Across 72 studies, disturbed sleep was linked with higher CRP and IL-6, two markers of systemic inflammation.
- It impairs you like alcohol. After 17 to 19 hours awake, performance on some tests was as bad as, or worse than, at a blood alcohol concentration of 0.05%.
- It's dangerous on the road. Drowsiness while driving, unrelated to alcohol, is responsible for serious crash injuries and deaths.
- It makes it harder to learn and focus. Sleep deficiency can leave you struggling to learn, concentrate and react.
- It weighs on your mood. Sleep deficiency is linked with depression, along with high blood pressure and kidney disease.
- It's associated with a shorter life. In a meta-analysis of more than 1.3 million people, habitual short sleep was associated with a 12% higher risk of death. Very long sleep was too, so more is not always better.
- Disrupting your body clock carries risk. The World Health Organization's cancer agency classifies night shift work as probably carcinogenic to humans, because it repeatedly disrupts circadian rhythms.
What happens while you sleep?
Sleep is not one long, even state. Through the night you cycle through non-REM and REM sleep several times. In deep non-REM sleep your heart rate and breathing slow and your muscles relax. In REM sleep your brain becomes much more active, your eyes move quickly behind closed lids and most vivid dreaming happens. Both stages matter for waking up rested.
Do naps count?
A nap won't replace a full night, but it can help. In a study of people who had slept only five hours, a 10-minute afternoon nap improved alertness, fatigue and performance almost immediately, with benefits lasting up to 155 minutes. Naps of 30 minutes caused a period of grogginess first. If you nap, keep it short and early in the afternoon.
How can you get more sleep starting tonight?
- Keep the same bedtime and wake time, even on weekends.
- Stop caffeine by early afternoon, and put screens away before bed.
- Keep your bedroom cool, dark and quiet.
- Build a wind-down routine. Some people like a warm drink; others add magnesium. Magnificent, our 4-in-1 magnesium powder, is made to support sleep and muscle relaxation.
For more on why you might feel wiped out even after a full night, read why am I so tired all the time? and our tips for having more energy, naturally. If you snore loudly, wake up gasping or feel sleepy despite a full night, talk to your doctor: sleep disorders like sleep apnea are common and treatable.
So take this as your permission: go to bed.
