Do women who work at night or on rotating shifts have less chance of becoming pregnant? According to one study it would be likely, at least they have shown with mice that circadian rhythm negatively influences fertility.
Recall that circadian rhythms (from the Latin circa, which means 'around' and dies, meaning 'day') or biological rhythms are oscillations of biological variables at regular intervals of time, regulated by sunlight and temperature.
A study recently published in "PLoS ONE" demonstrates for the first time the association between the disruption of circadian rhythms and the physiology of reproduction. The work is titled "Environmental Perturbation of the Circadian Clock Disrupts Pregnancy in the Mouse" ('The disturbance of the circadian clock environment alters pregnancy in the mouse').
Researchers led by Fred W. Turek of the Northwestern's Center for Sleep and Circadian Biology studied three groups of female mice that had mated during the 21 days that these animals usually last.
One of the groups, considered control (composed of 12 rats), lived according to the normal circadian rhythm, 12 hours of light versus 12 of darkness. Transferred to women, this group would correspond to those who work or sleep at a normal time.
The second, called 'advanced phase' and composed of 18 animals, also experienced 12 hours a day of light but, five days a week, the light stage began six hours earlier than the other days. This group would correspond to women who work at night, Monday through Friday.
The last group, of delayed phase and also of 18 mice, lived in rotating shifts: every five days, their daylight hours were delayed six hours, experienced four different circadian rhythms during the study. They would be the women who work in rotating shifts that change every week.
The study authors point out that they were surprised at the results obtained, since they exceeded their expectations regarding greater degree of infertility in altered cycles. Specifically, the control group reached 90% of pregnancies, compared to 22% of the second group or 50% of the rotating shifts group.
What the authors observed, and report in the scientific journal, is that the chances of conceiving were reduced "considerably" according to exposure to light. According to them, these data have implications for the reproductive health of women who work in shifts, but also for those who have sleep disorders associated with circadian rhythms or those who have interrupted sleep for other reasons.
Now studies in people are needed to check if the woman's circadian rhythm could influence her chances of achieving pregnancy. Infertility could add to the problems associated with these dysfunctions in the rhythm of life of some people.
