WASO: Why Does It Increase with Age?

Insomnia is a common sleep disorder, especially for seniors. WASO (time awake after sleep onset), a component of insomnia, tends to increase with age. There are also many variations in WASO for seniors. To better under-stand the nature of insomnia, an equation was developed to predict WASO using maximum oxygen uptake (VO 2max ) as a measure of fitness associated with aerobic exercise. Predictions from the equation matched measured values with an R 2 = 0.98. The results were highly significant (p < 0.001). A second equation was used to predict VO 2max as a function of age and relative fitness (a measure of aerobic fitness independent of age). The two equations were combined to predict WASO as a function of age, gender, and relative fitness. Based on these results, it appears that aerobic exercise to improve relative fitness can be used to reduce WASO. The WASO model explains the numerous reports of reduced WASO associated with long-term exercise pro-grams. The model also explains why WASO increases with age and why high WASO values associate with early death.