T Nation

Sleep Duration/Quality Test Study

Thought people might like a look at this. . .

April 3, 2007 ? In a small cohort of men aged 64 to 74 years, the amount of nighttime sleep is linked with a significant variability in morning testosterone levels. The results of the study are reported in the April issue of Sleep.

“The circulating testosterone levels of healthy men decline with advancing age,” writes Plamen D. Penev, MD, PhD, from the University of Chicago in Illinois.

"This process is characterized by considerable inter-individual variability, the causes of which are of significant biological and clinical interest but remain poorly understood.

Since sleep quantity and quality decrease with age, and experimentally-induced sleep loss in young adults results in hormonal changes similar to those that occur spontaneously in the course of aging, this study examined whether some of the variability in circulating testosterone levels of older men can be related to objective differences in their sleep."

At a general community and university clinical research center, 12 healthy men aged 64 to 74 years provided 3 morning blood samples, which were pooled for measurement of total and free testosterone. Overnight laboratory polysomnography and wrist activity monitoring for 6 to 9 days were used to determine the amount of nighttime sleep both in the laboratory and in everyday life settings.

Primary outcome measures were total sleep time and morning testosterone levels. Sleep time in the laboratory was correlated with the usual amount of nighttime sleep at home (Pearson’s r, 0.842; P = .001).

Based on bivariate correlation and multiple linear regression analyses, the amount of nighttime sleep measured by polysomnography independently predicted the morning total (β 0.792; P = .017) and free (β 0.741; P = .029) testosterone levels.

“Objectively measured differences in the amount of nighttime sleep are associated with a significant part of the variability in the morning testosterone levels of healthy older men,” the author writes.

Study limitations include the decision to monitor sleep after all blood samples for androgens were drawn and inclusion only of a small group of healthy older men who met the strict screening criteria and were willing to undergo 2 nights of laboratory sleep monitoring, thus limiting generalizability.

“For the time being, these findings suggest that complaints of poor or insufficient sleep in otherwise healthy older men can be associated with a more pronounced age-related androgen decline,” Dr. Penev concludes. “Eliciting such sleep complaints in the physician’s office may facilitate the judicious interpretation of lower testosterone levels in the older male patient.”

The American Federation for Aging Research and the National Institutes of Health supported this study.

Sleep. 2007;30:427-432.