Sleep restriction and testosterone concentrations in young healthy males: randomized controlled studies of acute and chronic short sleep.
Level 2 - randomized trial
Individual randomized controlled trials
PubMed 31416797 · doi:10.1016/j.sleh.2019.07.003
What was done
Two randomized controlled studies evaluated the effects of sleep restriction (SR) versus habitual sleep (HS) on plasma testosterone levels in healthy young men. Study 1 was an inpatient trial (n = 14) comparing acute severe SR (4 hours time in bed) against HS (9 hours time in bed) for 5 nights, measuring plasma testosterone at baseline and end point. Study 2 was an outpatient trial (n = 13) comparing mild chronic SR (habitual sleep reduced by 1.5 hours per night) against HS for 6 weeks, with testosterone measured at baseline, week 3, and week 6. Linear models were used to analyze changes in testosterone concentrations.
What was found
In Study 1, acute SR showed no significant sleep-by-time interaction (change during HS: 22.86 ± 163.79 ng/dL; change during SR: 43.73 ± 159.96 ng/dL; P = .41) and no significant main effect of sleep duration (P = .13). In Study 2, 6 weeks of mild SR showed a trend toward a sleep-by-time interaction (P = .067) and a significant main effect of sleep on testosterone concentrations (P = .0046), with testosterone concentrations being slightly lower overall but increasing over time with SR relative to HS.
Why it matters
The findings challenge earlier evidence suggesting that sleep restriction necessarily lowers testosterone in healthy young men.
Limits
The study is constrained by very small sample sizes (14 and 13 participants) and wide variance in testosterone changes. It was conducted exclusively in young, healthy males, precluding generalization to older men, women, or individuals with sleep disorders. Diurnal hormone rhythmicity and free versus total testosterone fractions were not detailed in the abstract.
Cited by
- contradicts Men who get less sleep exhibit lower testosterone levels and lower sperm counts.