Parisa Vidafar, Elise M. McGlashan, Angus C. Burns, Clare Anderson, Ari Shechter, Steven W. Lockley, Andrew J. K. Phillips, Sean W. Cain
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引用次数: 0
Abstract
Women typically sleep and wake earlier than men and have been shown to have earlier circadian timing relative to the light/dark cycle that synchronizes the clock. A potential mechanism for earlier timing in women is an altered response of the circadian system to evening light. We characterized individual-level dose–response curves for light-induced melatonin suppression using a within-subjects protocol. Fifty-six participants (29 women, 27 men; aged 18–30 years) were exposed to a range of light illuminances (10, 30, 50, 100, 200, 400, and 2000 lux) using melatonin suppression relative to a dim control (<1 lux) as a marker of light sensitivity. Women were free from hormonal contraception. To examine the potential influence of sex hormones, estradiol and progesterone was examined in women and testosterone was examined in a subset of men. Menstrual phase was monitored using self-reports and estradiol and progesterone levels. Women exhibited significantly greater melatonin suppression than men under the 400-lux and 2000-lux conditions, but not under lower light conditions (10–200 lux). Light sensitivity did not differ by menstrual phase, nor was it associated with levels of estradiol, progesterone, or testosterone, suggesting the sex differences in light sensitivity were not acutely driven by circulating levels of sex hormones. These results suggest that sex differences in circadian timing are not due to differences in the response to dim/moderate light exposures typically experienced in the evening. The finding of increased bright light sensitivity in women suggests that sex differences in circadian timing could plausibly instead be driven by a greater sensitivity to phase-advancing effects of bright morning light.
期刊介绍:
The Journal of Pineal Research welcomes original scientific research on the pineal gland and melatonin in vertebrates, as well as the biological functions of melatonin in non-vertebrates, plants, and microorganisms. Criteria for publication include scientific importance, novelty, timeliness, and clarity of presentation. The journal considers experimental data that challenge current thinking and welcomes case reports contributing to understanding the pineal gland and melatonin research. Its aim is to serve researchers in all disciplines related to the pineal gland and melatonin.