Menstrual Phase Response to Nocturnal Light

Abstract

The aims of the study were to test whether nocturnal white light can normalize menstrual cycles in oligomenorrheic women, and whether the phase of the menstrual cycle in which light is given is important for the shortening effect. Twenty-five women with long menstrual cycles (35.9-53.4 days on average) were treated for 1-3 cycles, each of which was preceded and followed by at least two untreated cycles. Treatments were 100 watt bedside lights administered for 5 consecutive nights. They centered at three different phases of the menstrual cycle: 6-7th, 14-17th or 23-25th days of the treated cycle (early, middle or late treatment, respectively). On average, the treatment cycle lengths were modestly, but significantly reduced compared to the duration of baseline cycles (more than 11%). The difference in the effects of the early, middle and late treatment was not significant. However, if middle or late treatments were administered in the latter half of the interval between the menstrual cycle onset and probable time of ovulation, reductions of the treated cycle length were substantial (more than 20%, resulting in cycles less than 33 days on average; p < 0.001). Other treatments produced only weak (up to 7%), if any, cycle reductions. Moreover, we found a strong correlation (p < 0.001) between the duration of baseline cycle and differential effect of middle treatment (compared to early or late treatment). Middle treatments reduced treated cycle duration to the normal range in the subjects with shorter mean baseline cycles (<42 days), while in the subjects with longer duration of baseline cycle the shortening effect was produced by late treatments (p = 0.005 and p = 0.001, respectively). The results support the suggestion that a bedside lamp used on nights prior to ovulation can cause reduction of long menstrual cycles.

Stimulatory Effect of Morning Bright Light on Reproductive Hormones and Ovulation: Results of a Controlled Crossover Trial

“…We did not find a significant shortening of the menstrual cycle following light exposure. Whilst this was also the case in the last menstrual cycle study of the San Diego group [8], in previous studies the shortening effect had been shown consistently [3–7,9]. The cause of this discrepancy is unclear.…”

“…Both the baseline and follow-up investigations were planned to be performed in follicular phase before ovulation, because the dominant follicle ruptures and the hormonal profile changes very considerably on ovulation and this might confound consistency of our results, especially if not all cycles are ovulatory. On the other hand, light exposure is most effective when administered around the days of presumed ovulation [7]. Therefore, the approximate day for entering the study was calculated as minimal cycle length (for a particular woman) minus 14 d (usual duration of the luteal phase) and minus 7 d (duration of the light treatment).…”

“…Forty years ago it was asserted that light might regulate the menstrual cycle and ovulation [2]. A series of six studies—one in the Boston area, four in San Diego, and one in Novosibirsk (1965–1995)—have shown that the menstrual cycle shortened in women with long menstrual cycles after bedside light administered overnight around the days of presumed ovulation [3–7]. Two subsequent studies found an increased rate of ovulation determined with a home dip-stick test detecting an ovulatory surge of LH in urine ([8], Putilov et al, unpublished data].…”

“…Women with slightly lengthened menstrual cycles were selected with a view to shortening the cycle, i.e., a sort of treatment since in woman with normal cycles this shortening could be undesirable [9]. On the other hand, women with very long menstrual cycles (mean >42 d) are only slightly responsive to light exposure [7], suggesting that significant hormonal abnormalities are not subject to a relatively subtle intervention such as light therapy.…”

Weak evidence of bright light effects on human LH and FSH

“…In men, an increase in testosterone production might lead to increased fertility in some younger men, and palliation of loss of libido, erectile dysfunction, and muscle wasting among older men. In women, light stimulation might promote fertility as well as regularize the menstrual cycle [ 55 , 61 ]. In both genders, bright light augmentation of gonadotropins might be one aspect of the antidepressant benefits [ 62 - 64 ].…”