Changes in testosterone with differing sleep schedules

Lindsey Ann Tompkins

Testosterone is the focus of several studies in sleep research. This study examined the effect of split sleep in comparison to consolidated daytime and consolidated nighttime sleep on plasma testosterone prior to and at the end of a 5-day work week. This was part of a larger study designed to detect sleep schedule-related perturbations in physiological parameters relevant to chronic illness. Fifty-three healthy males (26.6±4.0y) participated in a controlled laboratory experiment. Participants underwent 2 baseline days (10h; time in bed (TIB) 22:00-08:00) before being randomized to a 5-day work week with either a daytime sleep (N=17; TIB 10:00-20:00), split sleep (N=17; split-shift with morning and afternoon sleep; TIB 03:00-08:00 and 15:00-20:00) or nighttime sleep (N=19; TIB 22:00-08:00). After the workweek, subjects then had recovery sleep of 10h TIB (22:00-08:00). Total sleep opportunity per day was equal (10 hr) for the three sleep iv conditions during the workweek. However, in the 24 hours prior to the second series of blood draws, the daytime sleep condition had 15 hours of sleep opportunity vs. 10 hours for the nighttime and split sleep conditions. Blood was taken by intravenous catheter on study days 2 and 9 at 09:00, 10:00, 12:00, 14:00, 16:00, 18:00, and 20:00. Plasma samples were assayed for testosterone by Quest Diagnostics. A linear mixed-effects model was used to examine the effect of sleep condition (daytime, split, nighttime), work week (pre, post) and time of day on testosterone, controlling for age and body mass index (BMI). Sleep condition did not differentially affect testosterone (F[2, 47.95]=2.33, p=0.10). There was a main effect of time of day on testosterone, with highest levels at the 09:00 draw for all sleep conditions (F[6,157.17]=67.02,p<0.001). There was a significant interaction of condition by week (F[2,561.43]=10.08, p<0.001) with testosterone higher in the daytime sleep condition after the work week. Our finding is best explained by the daytime sleep group having a longer sleep opportunity in the 24 hours prior to the second blood draw. These data confirm and extend previous findings that testosterone is highest post sleep, falls during waking, and is responsive to acute changes in sleep/wake history.

Changes in testosterone with differing sleep schedules

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