highly significantp < 0.0001
Age and Sex Effects on 24-h Vigilance-State Profiles The age × hour interaction was highly significant for all four vigilance states by ML likelihood-ratio test: TDW (χ 2 (23) = 258.2, p < 0.0001), nTDW (χ 2 (23) = 151.6, p < 0.0001), NREM (χ 2 (23) = 110.4, p < 0.0001), and REM (χ 2 (23) = 81.7, p < 0.0001).