Table 1.
Circadian period estimates
| Subject | Age, years | Gender | τOBSm, hr ± SD | (95% CI), hr | τm, hr ± SD | τt, hr ± SD |
|---|---|---|---|---|---|---|
| T cycle = 24.0 h | ||||||
| 18G6 | 20 | M | 23.97 ± 0.03 | (23.92–24.02) | 23.88 ± 0.01 | 23.88 ± 0.04 |
| 1814 | 24 | M | 23.96 ± 0.02 | (23.91–24.01) | 23.92 ± 0.01 | 23.91 ± 0.05 |
| 1842 | 38 | M | 23.98 ± 0.04 | (23.89–24.06) | — | — |
| 1983 | 38 | F | 24.02 ± 0.05 | (23.92–24.12) | 24.06 ± 0.03 | 24.08 ± 0.07 |
| 19A4 | 24 | M | 24.06 ± 0.04 | (23.98–24.14) | 24.12 ± 0.02 | 24.14 ± 0.04 |
| 18G1 | 31 | M | 24.27 ± 0.03 | (24.21–24.32) | 24.36 ± 0.01 | 24.48 ± 0.05 |
| T cycle = 23.5 h* | ||||||
| 2029 | 28 | M | 23.89 ± 0.09 | (22.79–24.99) | — | — |
| 19F8 | 44 | M | 24.14 ± 0.02 | (24.05–24.22) | — | — |
| 2028 | 26 | M | 24.19 ± 0.03 | (23.76–24.62) | — | — |
| T cycle = 24.6 h | ||||||
| 1916 | 37 | M | 23.87 ± 0.03 | (23.82–23.92) | 23.77 ± 0.01 | 23.77 ± 0.04 |
| 18J5 | 31 | M | 24.02 ± 0.03 | (23.96–24.07) | 23.93 ± 0.01 | 23.95 ± 0.07 |
| 1715 | 27 | M | 24.35 ± 0.01 | (24.33–24.37) | — | — |
| 1922 | 33 | M | 24.34 ± 0.03 | (24.28–24.39) | 24.16 ± 0.01 | 24.07 ± 0.05 |
| 19A9 | 40 | F | 24.34 ± 0.03 | (24.29–24.39) | 24.20 ± 0.03 | 24.16 ± 0.08 |
| 1947 | 41 | F | 24.40 ± 0.03 | (24.35–24.45) | 24.23 ± 0.01 | 24.22 ± 0.09 |
| Range 20–44 | 23.77–24.36 | 23.77–24.48 | ||||
Observed plasma melatonin rhythm (τOBSm) during imposed 24.0-, 23.5-, and 24.6-h days and 95% confidence intervals; intrinsic circadian period as estimated by melatonin (τm) and core body temperature (τt) rhythms during forced desynchrony (T = 28 h). For each subject, the periods of the (τm) versus the (τt) rhythms during forced desynchrony were strongly correlated (Pearson correlation: r = 0.97; P < 0.0001). Period estimates were not available in five subjects because the forced desynchrony protocol was not conducted.
*
Because of the few data points collected, observed periods estimates and 95% CI for T = 23.5 h were derived from linear fits of melatonin onsets during CRs and day 14 (Fig. 1a).