Six nights of four hours in bed were enough to push the glucose tolerance of eleven healthy young men sharply down. Their evening cortisol ran higher too (PMID 10543671). Sleep deprivation is more than feeling tired. It shifts things a laboratory can simply measure.
What strikes me about the Dutch search results: almost everything on page one comes from mattress retailers, bedding shops and supplement stores. Not one page names a primary source.
That is a shame, because the research exists. And it comes with numbers.
Below is what sleep deprivation did to cortisol, insulin sensitivity, testosterone, hs-CRP, leptin and ghrelin in controlled trials. Plus what you can have measured yourself.
What are the symptoms of sleep deprivation?
The best known are daytime sleepiness, a shorter fuse, trouble concentrating and a slower reaction time. On top of that come stronger cravings for sweet and fatty food, more frequent colds and a memory that keeps slipping. These complaints rarely arrive alone. They stack up over days.
The Hersenstichting, the Dutch brain foundation, describes sleep as the window in which your brain clears up and fixes memory traces. Sleep too little and that work stays half done.
You notice it in your attention first.
Reaction time is the most sensitive measure here. A few short nights in a row produce more moments in which you register nothing at all. You rarely notice those moments yourself.
- Daytime. Sleepiness, trouble concentrating, irritability and a slower reaction time.
- Appetite. More hunger, and a pull towards carbohydrate-rich and fatty food.
- Physical. Headaches, muscle soreness that lingers, a higher resting heart rate and sometimes a higher blood pressure.
- Mood. Low spirits, less patience, quicker emotional reactions.
If those complaints persist while you do log the hours, something else is probably in play. Our overview of causes of persistent fatigue and which blood values give insight walks through the options.
How do you know you are sleep deprived?
Three signals. How fast you fall asleep, how much longer you sleep at the weekend, and whether you wake without an alarm. If you drop off on the sofa within five minutes, sleep two hours longer on Saturday than on a weekday, and always need the alarm, you are running sleep debt.
Sleep debt is not a medical term, but it describes the situation well. Every night shorter than what you need puts something on the tab.
Most adults need seven to nine hours. A small group genuinely does fine on less, and that is genetics rather than willpower.
Six hours feels like enough to a lot of people. In performance tests it often is not. What too little sleep does in practice sits in the piece on whether six hours of sleep is enough.
Quality counts too. Eight hours of light, broken sleep is a different thing from eight hours with enough deep sleep. That is the subject of the article on how much deep sleep you need.
Which blood values change with sleep deprivation?
Mainly insulin sensitivity, evening cortisol, testosterone in men and inflammatory markers such as hs-CRP. Alongside those, leptin falls and ghrelin rises, the two hormones that steer hunger and fullness. These are group averages under tightly controlled conditions, not a result yours has to match.
Here is what those studies actually measured, value by value.
| Blood value | What happens with sleep deprivation | Source |
|---|---|---|
| Insulin sensitivity and glucose tolerance | After six nights of four hours, glucose tolerance fell and the early insulin response slowed in eleven healthy young men. | Spiegel, Lancet 1999 (PMID 10543671) |
| Morning and evening cortisol | Late-afternoon and evening cortisol ran higher, and the normal decline towards the evening was slower. | Spiegel, Lancet 1999 (PMID 10543671) |
| Testosterone (men) | One week of five hours of sleep went together with roughly 10 to 15 percent lower daytime testosterone in ten young men. | Leproult, JAMA 2011 (PMID 21632481) |
| hs-CRP and IL-6 | Sleep disturbance was associated with higher CRP and higher IL-6. Short sleep duration was associated with higher CRP, but not with IL-6. | Irwin, Biol Psychiatry 2016 (PMID 26140821) |
| Leptin and ghrelin | After two nights of four hours, leptin sat about 18 percent lower and ghrelin about 28 percent higher, with more hunger and stronger appetite for calorie-dense food. | Spiegel, Ann Intern Med 2004 (PMID 15583226) |
These numbers come from sleep laboratories, where participants followed a fixed schedule. Your own result also depends on your age, your training load, an infection you are recovering from and the time of the draw.
Take two men of 34 who both sleep six hours. One has an hs-CRP of 0.7 mg/L and a testosterone of 21 nmol/L. The other sits at 3.9 mg/L and 12 nmol/L, and trains hard four times a week on top of that.
Same sleep duration, very different result.
For the second man, training itself can push hs-CRP up temporarily, and a low testosterone value can belong to several things at once. One measurement on one morning does not settle that. A repeat a few weeks later, at the same time of day, says more.
How sleep and blood values connect more broadly sits in poor sleep and your blood values.
How can too little sleep affect your blood sugar?
Roughly through two routes. Evening cortisol stays higher, and cortisol works against the uptake of glucose into your cells. At the same time your autonomic nervous system shifts towards the sympathetic side, which can dampen insulin release from your pancreas. Both routes push the same way.
One experiment shows that route nicely. Researchers held cortisol and testosterone artificially fixed in men during sleep restriction. The drop in insulin sensitivity that normally follows turned out smaller (PMID 34043794).
That makes these two hormones plausible as an intermediate step, not as the whole explanation.
What I like about it: it is one of the few studies that does not only show an association, but turns a dial to see what happens. That is a good deal more convincing than a correlation.
What does years of sleep deprivation do to you?
At group level, chronic sleep deprivation is associated with a higher risk of cardiovascular disease, type 2 diabetes and death. A meta-analysis of prospective studies found a modestly raised all-cause mortality risk with short sleep duration, around 12 percent (PMID 20469800). That is an association in large groups, not a prediction for you.
I think that distinction is worth repeating. A twelve percent increase in a cohort of hundreds of thousands of people says something about that group. About your coming year it says very little.
More practical is this: chronic sleep deprivation keeps the shifts in the table above in place. One short night is an outlier. Months of five-hour nights is a different situation.
Inflammatory markers show that well. The Irwin meta-analysis found its clearest associations with persistent sleep disturbance, not with a single bad week (PMID 26140821).
Your immune system belongs in this picture too. People who habitually sleep short report respiratory infections more often, although more than sleep alone plays a part there.
The NHG-Standaard Slaapproblemen en slaapmiddelen, the guideline Dutch GPs work with, treats long-standing insomnia as something that belongs in a conversation with your GP. That seems like the right place for it to me.
How long does it take to catch up on sleep debt?
Longer than one weekend. Your sleepiness usually settles within a few days of extra sleep, but attention and reaction time lag behind it. In the sleep laboratories that studied this question, several nights of normal length were needed before the measurements returned to baseline.
So catching up does work, just not one for one.
An eleven-hour lie-in on Saturday does not repair a week of five-hour nights. What tends to work better is raising the floor: half an hour earlier to bed every night, instead of one long night per week.
What the research says actually helps you sleep better sits in the article on sleeping better.
And if you do log the hours yet still wake up tired, sleep deprivation is probably not your main suspect.
What can you measure with chronic sleep deprivation?
The values that moved in the studies are ones a laboratory can simply run: fasting glucose, HbA1c, cortisol, testosterone in men, hs-CRP and your thyroid values. They do not prove sleep deprivation, and they do not make a diagnosis. They do show whether something else is contributing to your fatigue, which is exactly what mattress advice never gives you.
Ferritin and vitamin B12 belong on that list as far as I am concerned. Low iron produces complaints that look a lot like sleep deprivation, and you cannot feel the difference.
Practically: the fatigue panel covers most of those values. If you want glucose, HbA1c and your lipids alongside them, the extended health checkup is the broader option.
Give blood fasted and in the morning where possible, certainly if cortisol and testosterone are included. Both swing strongly across the day, and an afternoon draw makes the result hard to read.
Concretely: log your bedtime and your wake time for a week, and note how you felt at three in the afternoon. Take that list to your GP if the complaints persist. A week of real data is a better starting point than an estimate after the fact.
References
- Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. Lancet. 1999;354(9188):1435-1439. PMID 10543671.
- Spiegel K, Tasali E, Penev P, Van Cauter E. Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004;141(11):846-850. PMID 15583226.
- Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA. 2011;305(21):2173-2174. PMID 21632481.
- Irwin MR, Olmstead R, Carroll JE. Sleep disturbance, sleep duration, and inflammation: a systematic review and meta-analysis of cohort studies and experimental sleep deprivation. Biol Psychiatry. 2016;80(1):40-52. PMID 26140821.
- Cappuccio FP, D'Elia L, Strazzullo P, Miller MA. Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep. 2010;33(5):585-592. PMID 20469800.
- Clamping cortisol and testosterone mitigates the development of insulin resistance during sleep restriction in men. J Clin Endocrinol Metab. 2021. PMID 34043794.
- Hersenstichting, information on sleep and the brain, and the NHG-Standaard Slaapproblemen en slaapmiddelen.
This article is informational and does not replace medical advice. Blood values are a snapshot and say nothing about a diagnosis on their own. Every result at Vitalcheck is reviewed by a BIG-registered doctor. If your symptoms persist or get worse, contact your GP.
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