Age-related changes in slow wave sleep and REM sleep and relationship with growth hormone and cortisol levels in healthy men

Context In young adults, sleep affects the regulation of growth hormone (GH) and cortisol. The relationship between decreased sleep quality in older adults and age-related changes in the regulation of GH and cortisol is unknown. Objective To determine the chronology of age-related changes in sleep duration and quality (sleep stages) in healthy men and whether concomitant alterations occur in GH and cortisol levels. Design and Setting Data combined from a series of studies conducted between 1985 and 1999 at 4 laboratories. Subjects A total of 149 healthy men. aged 16 to 83 years, with a mean (SD) body mass index of 24.1 (2.3) kg/m(2), without sleep complaints or histories of endocrine, psychiatric, or sleep disorders. Main Outcome Measures Twenty-four-hour profiles of plasma GH and cortisol levels and polygraphic sleep recordings. Results The mean (SEM) percentage of deep slow wave sleep decreased from 18.9% (1.3%) during early adulthood (age 16-25 years) to 3.4% (1.0%) during midlife (age 36-50 years) and was replaced by lighter sleep (stages 1 and 2) without significant increases in sleep fragmentation or decreases in rapid eye movement (REM) sleep. The transition from midlife to late life (age 71-83 years) involved no further significant decrease in slow wave sleep but an increase in time awake of 28 minutes per decade at the expense of decreases in both light non-REM sleep (-24 minutes per decade; P<.001) and REM sleep (-10 minutes per decade; P<.001). The decline in slow wave sleep from early adulthood to midlife was paralleled by a major decline in GH secretion (-372 mu g per decade; P<.001). From midlife to late life, GH secretion further declined at a slower rate (-43 mu g per decade; P<.02). Independently of age, the amount of GH secretion was significantly associated with slow wave sleep (P<.001). Increasing age was associated with an elevation of evening cortisol levels (+19.3 nmol/L per decade; P<.001) that became significant only after age 50 years, when sleep became more fragmented and REM sleep declined. A trend for an association between lower amounts of REM sleep and higher evening cortisol concentrations independent of age was detected (P<.10). Conclusions In men, age-related changes in slow wave sleep and REM sleep occur with markedly different chronologies and are each associated with specific hormonal alterations. Future studies should evaluate whether strategies to enhance sleep quality may have beneficial hormonal effects.