Figure 2.

Entrained Rest-Activity and Urinary 6-Sulphatoxymelatonin Rhythms in Two Blind Subjects

The daily activity rhythm (black) and light (lux) exposure (yellow) patterns of the female (A) and male (B) subjects, recorded at home for 3–4 weeks with wrist actigraphy (Actiwatch-L, Minimitter, New York). Data are double-plotted, with consecutive days plotted next to and beneath each other. The gray bars represent an arbitrary “night” from 23:00–6:00 hr for visual reference.

Analysis of actigraphy data indicated that both the female and male subject had sleep onset (mean ± standard deviation [SD] sleep onset = 21:50 ± 1:09 hr and 23:22 ± 0:24 hr, respectively) and sleep offset (8:38 ± 1:29 hr and 6:31 ± 0:26 hr, respectively) times that fell within the range of actigraphically derived sleep times for blind subjects with previously confirmed normally phased circadian sleep and urinary 6-sulphatoxymelatonin rhythms (mean ± 2SD sleep onset = 23:31 ± 2:26 hr, sleep offset = 7:11 ± 2:24 hr) [3, 14]. The urinary 6-sulphatoxymelatonin (aMT6s) rhythm peak time (○) in the male subject confirmed the presence of a normally phased nighttime 24 hr rhythm (mean ± SD = 3:00 ± 1:17 hr) that exhibited a normal phase angle (3:38 hr) with respect to the sleep/wake cycle based on previous studies in entrained blind subjects (mean ±2SD phase angle, sleep onset − aMT6s peak = 4:38 ± 2:28 [3, 14]). The raw urinary data are shown in [C] with the normal peak-time range for the aMT6s rhythms shown in gray (1:42–6:36 hr) [3].