Ethnic differences in the duration and amount of menstrual bleeding during the postmenarcheal period.

In 1989, 125 African-American and 123 European-American girls aged 12-14 years living in Durham, North Carolina, were enrolled in a 2-year study in which they maintained a menstrual calendar, recording the date and amount of menstrual bleeding. Weight, exercise, and stress during the previous week were recorded at the start of the menstrual cycle. Ethnicity was the strongest determinant of the duration of menstrual bleeding and of the probability of heavy bleeding. The mean duration of bleeding was 5.1 days for African-American girls and 5.6 days for European-American girls. Low body mass index, high stress, and dieting also influenced bleed duration, but the effects of low body mass index and stress were modified by ethnicity. european-American girls were less likely to have an episode of heavy bleeding (odds ratio = 0.48) than were African-American girls, while high stress increased the risk of having heavy bleeding episode (odds ratio = 1.51). Further investigation of potential ethnic differences in menstrual bleeding characteristics and of the role of stress in provoking heavy bleeding is warranted.