Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 50, Issue 4 M222-M226, Copyright © 1995 by The Gerontological Society of America
Higher plasma IGF-1 levels are associated with increased delta sleep in healthy older men
PN Prinz, KE Moe, EM Dulberg, LH Larsen, MV Vitiello, B Toivola and GR Merriam
Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, USA.
BACKGROUND. Sleep quality declines with age, with less time in deep or slow
wave sleep (SWS) and reduced amplitude of the delta waves that characterize
it. Age-related declines also occur in lean body mass, growth hormone (GH),
and insulin-like growth factor 1 (IGF-1). These changes in sleep quality
and anabolic status may be related, as administration of GH or growth
hormone releasing hormone (GHRH) can enhance SWS and decrease awakenings in
young men. Here we examine the relationship between plasma IGF levels and
delta sleep quality in older men. METHODS. The sleep EEG of 30 healthy
elderly men (64 +/- 6 yrs; range 50-75) was recorded on the second of 2
consecutive nights. Plasma samples were drawn within 3 weeks of EEG
recording, and IGF levels were assayed by RIA after acid extraction.
RESULTS. IGF explained 28% (semi- partial correlation coefficient r = .53;
p = .003) of the variance in average delta energy per epoch of SWS, after
age-related variance was removed. Higher IGF was associated with higher
average delta energy. Similar results were obtained for total delta energy
during SWS (r = .37, p = .04) 4nd time spent in SWS (r = .42, p = .02).
Other measures of sleep quality (e.g., wakefulness, REM sleep) were not
correlated with IGF. The IGF delta relationship was minimally influenced by
moderator variables such as thyroxine (T3, T4), and/or body mass index
(BMI). CONCLUSION. We conclude that age-adjusted IGF levels in healthy
senior men co-vary significantly with SWS and the delta energy that
characterizes it.
