RCTHumann = Study 1: n=14, Study 2: n=132019
Sleep restriction and testosterone concentrations in young healthy males: randomized controlled studies of acute and chronic short sleep.
Plain-language summary
This study looked at whether cutting sleep short changes testosterone in healthy young men, across two separate trials. In the first, 14 men had 4 hours in bed for 5 nights against 9 hours, and testosterone did not show a significant change. In the second, 13 men slept 1.5 hours less than usual for 6 weeks, and here sleep did have a significant effect, with testosterone slightly lower under restriction. So the severe short cut did nothing detectable and the mild long one did, which is the opposite of what most people would expect.
Key findings
- Severe short-term sleep restriction, 4 hours a night for 5 nights, did not show a significant change in testosterone.
- Mild long-term restriction, 1.5 hours less than usual for 6 weeks, did produce a significant effect, with testosterone slightly lower than under habitual sleep.
- The two trials point in different directions, and the longer, milder one is the one that moved testosterone.
How to analyze the study yourself
- Study type
- Randomized trials assign people to groups by chance, so differences between groups are unlikely to come from who chose what, but the small sample sizes here limit how broadly the findings can be applied.
- Population
- Healthy young men
- Funding
- NIH extramural
- Takeaway
- This study found that five nights of severe sleep loss did not show a significant change in testosterone, while six weeks of losing only 90 minutes a night did lower it slightly. If you are running a small sleep debt every night, the length of time you keep it up may matter more than how bad any single week gets.