The hypothalamic-pituitary-adrenal (HPA) axis in GF children shows no diurnal damping. Cortisol does not flatten at night. Instead, it begins its morning surge at 2 AM, reaching wake-up levels by 3:30 AM.
Researchers hypothesized that "germ-free" life might alter metabolic baselines, which in turn could influence sleep-wake cycles. Analysis of "Early Awakening" Phenomena early awakening report 14 and under 1973 germ free