What Good Sleep Does for Body and Mind – the Research

The most-cited recommendation comes from an 18-member expert panel of the American National Sleep Foundation: 7 to 9 hours for adults aged 18 to 64, and 7 to 8 hours from 65 onwards. The right reading matters – this is a scientific consensus guideline, not a rigid rule; individual needs vary. If you are awake and productive during the day without artificial aids, you are usually getting it right.

The most striking single finding comes from a study in which 164 healthy adults were exposed to a cold virus under controlled conditions after a week of measured sleep: those who had slept 6 hours or less fell ill around four times more often than people with more than 7 hours of sleep. A comprehensive review in Physiological Reviews puts this in context: sufficient sleep is associated with lower infection risk and better vaccine responses, while chronic sleep deprivation is associated with persistent low-grade inflammation. The authors also stress that causality in humans has not been conclusively proven – these are strong associations, not guarantees.

Among the best-replicated findings of sleep research is sleep's role in memory: newly learned material is reactivated primarily during deep sleep and transferred into long-term storage – researchers speak of active system consolidation. On the other side stands the risk of sleep deprivation: a meta-analysis of 17 studies puts the accident risk when drowsy at the wheel at around two and a half times. Cardiovascular associations are documented as well – both very short and very long sleep are associated in prospective studies with an increased risk of coronary heart disease and stroke, though the authors explicitly describe sleep duration as a marker, not a proven cause.

How relevant the topic is in Switzerland is shown by the figures from the Bundesamt für Statistik (Swiss Federal Statistical Office): in the Swiss Health Survey 2022, around a third of the population reported sleep disorders – 26 percent moderate and 7 percent pathological. Women, at 37 percent, are affected more often than men at 29 percent, and the share has risen since 1997. Persistent sleep problems belong in medical evaluation – they can have many causes, from stress to sleep apnoea to illness.

A bed cures nothing, and anyone promising otherwise leaves the ground of science. What the sleep environment can do is create good conditions. It is documented that sagging, poorly supporting sleep systems impair sleep, that trapped heat and moisture increase wake phases and reduce deep sleep, and that a medium-firm, individually fitted sleep surface performs best on average. If you give your sleep 7 to 9 hours and a well-fitted bed with a comfortable climate, you have laid the foundations you can influence – the rest is down to lifestyle, health and sometimes medical help.