Any type of eating disorder can boost a woman’s likelihood of having irregular menstrual periods, a new study confirms.

Based on the findings, “when someone’s got irregular menstruation, eating disorders should be on the radar screen,” Dr. Cynthia M. Bulik of the University of North Carolina at Chapel Hill, the study’s lead author, told Reuters Health. Missing periods raises a woman’s risk of osteoporosis, Bulik noted, and may also impair fertility.

According to current diagnostic criteria, anorexia nervosa is the only eating disorder subtype associated with menstrual irregularities, Bulik said. A woman must have absence of menstrual periods for at least three months to be diagnosed with anorexia nervosa.

But in a survey of 1,705 women participating in a genetic study who met strict diagnostic criteria for eating disorders, Bulik and her team found menstrual irregularities including absence of periods, skipping periods, and very light periods among women with every subtype of eating disorder, including bulimia nervosa.

Nearly 80 percent of women with anorexia reported secondary amenorrhea, meaning they had begun having periods before age 16 but had stopped menstruating for at least three months in a row at least once. About 36 percent of women with bulimia nervosa had secondary amenorrhea. Among women who fell into the “eating disorder not otherwise classified” group, 30.4 percent reported secondary amenorrhea.

The factors most strongly associated with menstrual dysfunction included a person’s body mass index (BMI), her calorie intake, and her level of exercise. Women who menstruated normally had the highest maximum and minimum lifetime BMIs, the researchers note, but even some women of normal weight reported menstrual irregularities.

The findings suggest to Bulik and her colleagues that menstrual status “might not be an informative criterion to distinguish among eating disorder subtypes.”

Doctors currently only screen patients for eating disorders if they are underweight, Bulik said. But based on her findings, she added, “menstrual irregularities should be a red flag for all physicians to ask about eating disorders.”

SOURCE: International Journal of Eating Disorders, July 2007.