title: Sleep Duration and Disturbances Were Associated With Testosterone Level, Muscle Mass, and Muscle Strength--A Cross-Sectional Study in 1274 Older Men.
abstract: 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.
  
  
  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.
authors.affiliation: Department of Medicine and Geriatrics, Pok Oi Hospital and Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China. Electronic address: auyeungtw@gmail.com.
authors.forename: Tung Wai
authors.initials: TW
authors.lastname: Auyeung
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Timothy
authors.initials: T
authors.lastname: Kwok
authors.affiliation: School of Public Health, The Chinese University of Hong Kong, Hong Kong, The Jockey Club Centre for Osteoporosis Care, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Jason
authors.initials: J
authors.lastname: Leung
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Jenny Shun Wah
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Centre for Bone and Arthritis Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Claes
authors.initials: C
authors.lastname: Ohlsson
authors.affiliation: Centre for Bone and Arthritis Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Vandenput
authors.affiliation: Department of Psychiatry, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Yun Kwok
authors.initials: YK
authors.lastname: Wing
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Jean
authors.initials: J
authors.lastname: Woo
mesh_terms: D000368:Aged; D000375:Aging; D003430:Cross-Sectional Studies; D006723:Hong Kong; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012890:Sleep; D012893:Sleep Wake Disorders / Q000209:etiology*; D011795:Surveys and Questionnaires; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone
keywords: Testosterone; muscle; old age; sleep