Abstract

PIP: To test the hypothesis that artificial light can be used to regularize the human menstrual cycle, 16 women with histories of menstrual irregularity and/or abnormally long cycles were studied. It was assumed that a 29-day cycle is the "normal" length. Thus, light exposure was begun on the evening of day 14, with the expectation that ovulation would be triggered by day 15 and menstruation on day 30. The light regimen was continued for 2-3 nights more. Temperature graphs indicated all subjects were ovulating. 41 control and 41 matching experimental cycle lengths were obtained. The experimental cycle lengths were less variable than the control lengths and showed a sharp peak at 29 days. In the 11 subjects exposed to light for more than 1 cycle, 9 showed a decrease in the range of cycle length (3.3% level of significance difference between control and experimental groups in terms of cycle length). It is concluded that these data provide evidence that photic stimulation can regularize menstrual cycle length and thus influence the time of ovulation, thereby facilitating use of the rhythm method of birth control. Further studies involving larger samples and more sophisticated measurements of ovulation in relation to photic stimulation are recommended.