The decrease in slow-wave sleep (N3) from midlife to late life parallels a decrease in which hormone?

• A. Growth Hormone
• B. Cortisol
• C. Melatonin
• D. Adrenaline

Answer: (A)

Slow-wave sleep is the deepest sleep stage where much of the body's restorative processes occur. Growth hormone is released primarily during slow-wave sleep, especially in the early part of the night, and both slow-wave sleep and growth hormone secretion decline with age. That parallel—less deep sleep accompanied by less growth hormone—explains why the decrease in N3 mirrors a decline in growth hormone. Cortisol follows a separate circadian pattern and is not driven by the depth of sleep, adrenaline isn’t tied to sleep stages, and while melatonin also drops with age, its changes are more about circadian timing than the depth of N3.