LACK OF SLEEP AFFECTS HORMONES
The changes in sleep quality that often come with age seem to trigger shifts in the endocrine system, altering hormone levels and metabolism. Researchers say that this study shows that a good night’s sleep may be a natural form of hormone therapy, particularly for older adults.
- Researchers studied 149 men, aged 16 to 83, and found that age-related changes in sleep quality were linked to specific changes in several hormones.
- As sleep quality and quantity declined levels of the adrenal hormone cortisol increased, while levels of Growth Hormone (GH) declined.
- After the age of 25, men experience a decline in deep sleep that accompanied by a drop in GH production. GH deficiency is related to reduced muscle mass and strength, increased fat tissue, weakened immunity to infection, and other health declines.
- In later years, a new sleep pattern emerges, in which men get less sleep overall and levels of cortisol go up. Elevated cortisol may underlie a host of mental and metabolic problems, including memory loss and insulin resistance — a precursor to diabetes.
The lower quality of sleep that the aging men experienced was evident though the measurement of several parameters.
- The average percentage of time spent in deep slow wave sleep decreased from 18.9% during early adulthood (age 16-25 years) to 3.4% during mid-life (age 36-50 years).
- This lost deep sleep was replaced by lighter sleep (stages 1 and 2) without other significant changes.
- The transition from mid-life to late life (age 71-83 years) involved no further significant decrease in deep slow wave sleep but an increase in time awake of 28 minutes per decade at the expense of decreases in both light non-REM (rapid eye movement) sleep and REM sleep.
These sleep pattern changes accompanied some changes in hormonal activity.
- The decline in slow wave sleep from early adulthood to mid-life was paralleled by a major decline in GH secretion (-372 µg per decade).
- From mid-life to late life, GH secretion further declined at a slower rate (-43 µg per decade).
- Independently of age, the amount of GH secretion was significantly associated with slow wave sleep.
- Increasing age was associated with an elevation of evening cortisol levels (+19.3 nmol/L per decade) that became significant only after age 50 years, when sleep became more fragmented and REM sleep declined.
These connections between hormones and shifting sleep patterns suggest that maintaining sleep quality throughout life may have important health benefits, according to Dr. Eve Van Cauter of the University of Chicago, Illinois, and colleagues.
Currently, studies are looking at whether GH replacement therapy might combat some of the effects of aging. Researchers note that their findings of a GH dip after age 25 suggest that such therapies “should target a younger age range than currently envisioned.”
The Journal of the American Medical Association August 16, 2000;284:861-868, 880-881.