June 13 (HealthDay News) -- Having delayed sleep phase syndrome (DSPS) appears to be linked to irregular menstrual cycles and increased premenstrual symptoms in women, according to a new report.

DSPS occurs when your internal clock is naturally out of sync with real time, so that staying up late and having difficulty waking early is your norm. It is unlike such conditions as jet lag, because external factors (time zone change, noise, light) do not cause your internal clock to desynchronize.

According to the new findings, women with delayed sleep phase syndrome were twice as likely to report an irregular menstrual cycle compared to control subjects. The frequency climbed to three times as many if the DSPS woman was not using birth control.

Cramps, mood swings and other premenstrual issues were reported by 69 percent of the women with delayed sleep phase syndrome, compared with almost 17 percent of those without the condition.

"While the data is preliminary, these results suggest that women with delayed sleep phase syndrome may be at increased risk for menstrual irregularity associated with circadian misalignment," study author Kari Sveum, of Northwestern University in Chicago, said in a prepared statement. "Further investigation with a larger group of subjects using prospective diary data would be useful to further establish the effects of circadian disruption on reproductive cycles in women with delayed sleep phase syndrome."

The results of the study, which analyzed questionnaires completed by 13 women with delayed sleep phase syndrome and 13 healthy women without DSPS, were presented this week at the annual meeting of the Associated Professional Sleep Societies in Baltimore.

SOURCE: American Academy of Sleep Medicine, news release, June 10, 2008