Sleep Duration and Disturbances Were Associated With Testosterone Level, Muscle Mass, and Muscle Strength--A Cross-Sectional Study in 1274 Older Men.

Background: Testosterone level follows a circadian rhythm. However, whether sleep duration and disturbances can affect testosterone level, muscle mass, and strength remains unknown.

Objective: To examine the relationship of sleep duration and disturbances to testosterone level, muscle mass, muscle strength, and walking speed.

Participants And Methods: We recruited 1274 community-dwelling men older than 65 years of age. Their early morning testosterone level was assayed by mass spectrometry. A sleep questionnaire was administered to enquire about their reported sleep duration, prolonged sleep latency (>0.5 hour), and subjective insomnia complaint. Muscle mass was measured by dual-energy x-ray absorptiometry. Testosterone level, muscle mass, handgrip strength, and walking speed were tested against sleep duration and disturbances.

Results: Testosterone increased with increasing sleep duration up to 9.9 hours, after which it decreased, giving rise to an inverted U-shaped relationship (P for quadratic trend <.05). A similar inverted U-shaped relationship occurred between sleep duration and muscle mass and function. Earlier go-to-bed time, despite being associated with a higher testosterone level (P < .05), was associated with weaker grip strength (P < .05). Earlier wake-up time was associated with higher muscle mass (P < .05) but neither grip strength nor walking speed. Neither prolonged sleep latency nor insomnia was associated with testosterone levels. However, prolonged sleep latency was associated with lower muscle mass (P < .05), weaker grip strength (P < .05), and slower walking speed (P < .001). Insomnia, on the other hand was associated with weaker grip strength (P < .05) and slower walking speed (P < .001) but not muscle mass.

Conclusions: Sleep duration and disturbances can affect testosterone level, muscle mass, and its function. Whether optimization of sleep can ameliorate age-associated decline in sex hormone and muscle performance warrants further studies.