Which statement best describes the overall trend in slow-wave sleep across early adulthood to midlife?

• A. It decreases
• B. It increases
• C. It remains unchanged
• D. It fluctuates

Answer: (A)

Slow-wave sleep is the deepest, most restorative stage of sleep (N3) and is strongest in younger adults. As people move from early adulthood into midlife, the amount of deep sleep typically declines. This shows up as shorter periods of N3 and reduced delta power, reflecting aging-related changes in brain structure and sleep-regulating systems. Because of these long-term changes, the overall trend is a decrease in slow-wave sleep. Short-term variability can happen from night to night, but the general pattern across this age span is downward.