Podcast episode 62 (in German)
Sleep: the biggest longevity lever fact-checked
September 1, 2026
In almost 60 episodes of this series, sleep was always level one, to which everything else referred. This episode delivers on that: what actually happens at night, why it is the biggest longevity lever — and how to set it with craft instead of pills.
What it is about
The episode first describes the night as a shift schedule: deep sleep in the first half of the night for body maintenance and growth hormone, REM sleep in the second half for memory and emotion, alternating roughly every 90 minutes. Then there is the glymphatic system, the nightly flushing of the brain. Then the question of quantity and its modern correction that regularity counts more than the number of hours. After that, the episode uses three studies to show what sleep deprivation concretely does — immune system, metabolism, hormones — and builds from this the counter-program of 5 points of craft. Finally, it covers trackers, naps, waking at night and a seven-day protocol to try for yourself.
Key points
- Deep sleep and REM sleep alternate roughly every 90 minutes; the largest growth hormone pulse of the day falls in the deep sleep of the first half of the night.
- Maiken Nedergaard described the glymphatic system in 2013: in deep sleep the interstitial spaces in the brain widen by up to 60 percent, and cerebrospinal fluid washes out metabolic waste such as beta-amyloid.
- The large cohorts show a U-curve with the optimum around 7 hours; the practical message remains 7 to 8 hours of opportunity to sleep, consistently kept.
- UK Biobank analyses with real motion sensors found a 20 to 40 percent lower risk of death in the most regular sleepers than in the most irregular — with the same amount of sleep.
- In Prather’s cold study, volunteers who slept less than 6 hours caught colds about 4 times as often as the 7-hour sleepers, although all were exposed to the same virus.
- One week of 5-hour nights lowered testosterone in young men by 10 to 15 percent; just a few nights of 4 to 5 hours push healthy people towards prediabetes.
- The craft in numbers: bedroom closer to 18 than to 22 degrees Celsius, power nap 10 to 20 minutes and before 3 p.m., last coffee before 2 p.m. because of the half-life of 5 to 6 hours.
Addendum (as of October 6, 2026): The figures on regularity come from large observational data. In the UK Biobank, regularity predicted the risk of death better than sleep duration; whether fixed sleep times or targeted sleep optimization extend life has not yet been tested by any intervention study. The pages Sleep & sleep hygiene and Consistent sleep times summarize the current state.
Where the data stop
A few findings need a footnote. The U-curve also shows higher mortality with long sleep, but long sleep is often a symptom rather than a cause — sick people sleep a lot. Genuine short-sleeper genes exist, but they are extremely rare; most people who get by on 5 hours have got used to their own tiredness. And sleep trackers measure the stages only approximately: their strength lies in trends, not in grades for individual nights, and sleep medicine now has a term for the anxiety about one’s own app: orthosomnia.
Individual bad nights are meaningless; the body catches up on deep sleep by itself, and composure is genuinely part of the therapy here. What, on the other hand, does not belong on an episode page: chronic sleep disorders, snoring with breathing pauses and leaden daytime sleepiness. Behind these there is often sleep apnea, which should be medically investigated and treated.
Listen (in German)
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Published on September 1, 2026.
The topic in the database
- Fixed times, a dark room, few late stimuli: sleep hygiene measurably improves insomnia complaints, but less than cognitive behavioral therapy. That targeted sleep optimization extends life in healthy people is not established.Sleep & sleep hygiene
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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-10-06.