“Sleep is a non-negotiable biological state for the maintenance of human life… our needs for sleep parallel those for air, food and water”1

It is only recently that we have been able to understand the importance of sleep. When we sleep our metabolic waste products are moved out of our brains. During non-Rapid Eye Movement sleep our brain is literally washed with cerebrospinal fluid( See Newsletter #186 for a decription of different types of sleep). The brain can show reduced performance after just one night of sleep deprivation. Studies have shown the buildup of beta-amyloid proteins in the brains of young heathy people, after one night. These are the same proteins considered as a precursor to Alzheimer’s Disease.

How Much Sleep Do We Need?

Researchers have looked at both the length of sleep and its regularity. In one longitudinal study of eight thousand people, they looked at sleep patterns. They followed people for over twenty five years. They looked at sleep duration between the ages of 50 and 60 and whether people subsequently developed dementia. People sleeping six hours or less had a 30% higher chance than those sleeping 7 hours or more.

More sleep does not necessarily bring more benefits. There is an optimal amount of sleep. Beyond 7-8 hours the curve reverses. More sleep has a negative impact on cognition and mental health. There are huge differences between countries on sleep. Using sleep trackers, the researchers compared 1.1 m people across the UK, the Netherlands and the USA. The US came out the worst. 30-40% of people slept less than 7 hours per night.

Regularity of sleeping patterns turns out to be as important. Using the UK Biobank researchers have looked at regularity and non-cognitive symptoms. They had nearly 100,000 people using sleep trackers. Regularity was measured by looking at the same time each night for two different times. Was the person awake or asleep and were they in the same kind of sleep. The looked over a week and created an index of regularity. The found that regularity reduced “all-cause mortality”. It was related to both “cardiovascular and cancer mortality”. Sleep is as important as food and air.

Sleep and Ageing

With age sleep patterns change for the worse. Our rhythms change, we wake earlier and need to go to bed earlier. (See Newsletter #049 "Early Birds and Night Owls".We could still make our 7 hours. Unfortunately, there are other changes. The proportion of non-REM sleep declines. It can be down by as much as 80-90%. At the same time, sleep efficiency drops. The percentage of time we are asleep when we are in bed falls. Our brainwasher is not nearly so efficient.

We know that heathy ageing requires sleep. At the same time ageing seems to be destroying sleep. Promoting better sleep is a growing issue. There are some things that are known to help. Going to bed and getting up at the same time works. So too does having a cool dark bedroom. The evidence for beds that maintain body temperature is however much patchier. Turning off blue light from computers is a must for young and old. Our biological clock is sensitive to blue light. Taking naps of less than an hour seems to have little effect on nighttime sleep (See Newsletter #194 "New Year Naps".

The jury is out on most pharmaceutical solutions. Melatonin has been subject to small scale trials. So too has magnesium. So far, few large-scale trials have been done or proved successful for sleeping pills. It does not matter whether they be pharmaceutical or “natural”. Talking therapies seem to help. “Cognitive behavioral therapy” seems to help. Unfortunately, it is very resource intensive and requires time and a trained therapist.

Will Your Smart Watch Help?

I have written about smart technology and trackers in other contexts.(Newsletter #184 "Do we really need a fitness tracker?" Measuring sleep poses the same issues. The systems can only measure certain things. Some use the accelerometer alone to assess the quality of sleep. How much we toss and turn in the night. Others add heart rate monitors, oxygen levels and even body temperatures. The key is the algorithm that combines these results to determine how much “good” sleep you have had. As feedback it might teach you that alcohol does not help sleep. Nor does a large meal before bed. It requires the user to link cause and effect. If not, the result can be a sleepless night worrying about what the sleep monitor is saying.

1. Michael Grander and Fabian'-Xose Fernandez “The translational neuroscience of sleep a contextual framework, Science, 374, 2021 568-73