Sleep Better

Lesson 1: Why sleep matters

Goal: understand what sleep does for you and what a little too little sleep, night after night, really costs.

Sleep isn’t the body switching off. It’s an active state in which the brain and body do maintenance work that can’t happen properly while you’re awake. Cut it short and the effects build up quietly, often without you noticing.

What sleep does

• Memory and learning. During sleep the brain replays and strengthens what you learned during the day. Deep sleep and REM sleep each seem to play a part. Practising something and then sleeping on it genuinely helps.
• Clearing the brain. A 2013 study in mice found that during sleep the spaces between brain cells widened by about 60%, letting fluid wash waste products out faster than during waking. This “glymphatic” clearance is still being studied in humans, but it’s one reason scientists describe sleep as housekeeping for the brain.
• Immunity. In a 2015 study, healthy adults were deliberately exposed to a cold virus. Those who had slept less than 6 hours a night the week before were 4.2 times more likely to catch the cold than those who slept more than 7.
• Mood and stress. Short sleep makes people more irritable, anxious and emotionally reactive. Ongoing insomnia is a known risk factor for depression.
• Appetite and metabolism. Short sleep shifts eating later into the evening and reduces how well the body handles sugar.

The cost creeps up on you

In a well-known 2003 experiment, volunteers were limited to 4, 6 or 8 hours in bed a night for two weeks. The 6-hour group’s attention and reaction times got steadily worse, until after two weeks they were as impaired as people who had stayed awake for one to two whole nights. The catch: they rated themselves as only slightly sleepy. You can’t trust how you feel to tell you how short of sleep you are.

Tired is like tipsy

Australian researchers compared tiredness with alcohol in the same people. After 17 to 19 hours awake (for most people, late evening after a normal day), performance on some tests was as bad as or worse than at a blood alcohol level of 0.05%, Australia’s legal driving limit. If you’ve been up since 6 am, a late drive home is not as safe as it feels.

Can you catch up at the weekend?

Partly. A lie-in pays back some of the debt, but a 2019 study found that weekend recovery sleep did not undo the metabolic effects of short weekday sleep, which returned as soon as short nights started again. Regular, enough sleep beats a weekly cycle of debt and repayment.

Try this

For the next three days, notice the time you first feel properly sleepy in the evening, and whether you feel rested in the first hour after waking. Don’t change anything yet; just notice.

Exercise 1

Write down two reasons that sleeping better matters to you personally (more patience with the kids, better training, a clearer head at work). You’ll come back to them in Lesson 14 when you set your plan.

Sources

• Xie et al. (2013), Sleep drives metabolite clearance from the adult brain, Science
• Prather et al. (2015), Behaviorally assessed sleep and susceptibility to the common cold, Sleep
• Van Dongen et al. (2003), The cumulative cost of additional wakefulness, Sleep
• Williamson & Feyer (2000), Moderate sleep deprivation produces impairments equivalent to legally prescribed levels of alcohol intoxication, Occupational and Environmental Medicine
• Depner et al. (2019), Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation, Current Biology

This course is general information, not medical advice. If you have ongoing sleep problems, loud snoring with pauses or gasping, or sleepiness that affects driving or work, see your doctor. In Australia, if you are struggling or feel unsafe, call Lifeline on 13 11 14.