Sweet Dreams was the title of a webinar by the International Longevity Centre. It provided a useful guide to whether we should worry about our sleep.

Sleep as an indicator of health.

It turns out that we use our perceived sleep quality to judge our health and wellbeing. It ranks as one of the top indicators. Perhaps this is why there is growing interest in the “sleep” function on the latest generation of fitness trackers (See Newsletter # 184 Do we Really Need a Fitness Tracker). Most people do not judge how well they are sleeping after a night of heavy drinking. We have all learned that alcohol may help us fall asleep, but it does no good to the quality of sleep thereafter. Instead, we all answer after a normal night.

Subjective sleep is a bad indicator. Dirk-Jan Dijk is a professor at the University of Surrey. His specialism is clinical research on sleep. He is also attached to their new Centre for Excellence in Ageing. He performed an interesting study in his sleep laboratory. He was able to track the details of an individual night’s sleep. How long it took to fall asleep. How much Rapid Eye Movement Sleep they had and how many times they woke up. How much of the important deep sleep they had. In the morning, he asked people how they slept.

It turns out that our assessment is based on only two things. It is negatively related to how many times we wake up. (Other studies have shown that many of these are only registered subconsciously). It was positively related to the amount of REM sleep. The important non-REM sleep was not part of the calculation. It is during this sleep that the brain is washed (See Newsletter #240 Brainwashing). It is this sleep that has been associated with the consolidation of our daily memories (See Newsletter #186 Sleeping on It). REM sleep represents only 20-25% of sleep in younger adults. In older people that can fall to 15%.

We should worry about changes in sleep patterns.

In the laboratory he was able to assess the impact of age on sleep. He asked respondents to remain in bed for 16 hours per day during the course of the experiment. This gave them ample opportunity to sleep for as long as they wanted. He used electrodes on the skull to track exactly when they fell asleep and woke. Across many subjects there were consistent patterns. The total amount of sleep goes down from 8.9 hours in the young to an average of 7.4 hours for the oldest group. REM sleep declines significantly with age and non-REM sleep goes down but not as much. If REM sleep is falling iy is not surprising that we think we are sleeping less well. Should we worry if we sleep longer or less?

The studies show that sleep deprivation is not good for cognitive ability. Apart from this, the current view is that we should only worry about significant changes in our sleep pattern. We all have a regular number of hours that we need to sleep to awake refreshed. If we continue to sleep 8.5 hours and have always done so, the fact that it is more than the 7.4 hours average is irrelevant. We know that older people will become more “morning” people. They will wake earlier. We may sleep less as the study shows. We may take short 30-minute naps in the afternoon (See Newsletter #194 New Year Naps). These changes are all normal

However it is other changes that are the potential warnings. Consistent extended sleep hours at night can be a warning of something else going on. Some studies have shown a relationship between sleeping longer and the onset of dementia. Longer naps in the daytime may be caused by an underlying physical illness. If the pattern changes it is worth consulting your doctor.

The Elders are not the Sleepy Ones.

It is common to assume that age brings with it sleepiness during the daytime. It is part of the ageing stereotype. Prof Dijk has proven the exact opposite. That is the young that are more likely to be tired in the day. He used two elegant studies. The first asked people of different ages to rate their tiredness at intervals during the day. Every two hours they completed the Karolinska Sleepiness Scale (KSS). This is a nine-point scale with “Extremely Alert” at one end. At the other end is “Fighting Sleep”. We have all been in a lecture or event and been forced to dig our nails into our palms to stop falling asleep. He could then plot the results against age as shown in the left hand chart. Clearly the 20-29 year olds felt more sleepy than any other group.His other study measures sleepiness by how easy it is for someone to fall asleep. At two hours intervals participants are asked to lie in a darkened room and try to sleep. Their sleep is tracked electronically. Asleep or still awake the exercise is ended after twenty minutes. Respondents return to their day until the next test. The chart on the right shows the result of this “multiple sleep latency test”. The results for each person are plotted against their age. The younger group found it easier to fall asleep, the older people took much longer.

Using either measure it is clear that older people are more awake. As the moderator of the session put it. “It you or your family are going on an over night bus trip it is better to choose the old driver”.

I hope my Newsletter did not put you to sleep. If it did, please Sleep Well.