Menstrual cycle abnormalities in healthy women with low physical activity. The North-Trøndelag population-based health study.

Background: Menstrual dysfunctions are often found in athletic women. This study evaluated the association between leisure time physical activity (LTPA) and menstrual function in healthy nonathletic women.

Methods: During 1984-1986, a population-based health survey (HUNT 1) was conducted in Nord-Trøndelag, Norway, with follow-up (HUNT 2) in 1995-1997. Women < 45 years old in HUNT 2 were included in the current study. LTPA was assessed by questionnaire in HUNT 1 and HUNT 2, and menstrual function by questionnaire in HUNT 2.

Results: Adjusted odds ratios (OR's) for long cycles were increased in women who reported < 1 hour of light LTPA (OR = 1.4, 95% CI = 1.0-2.0) and 1-2 hours (OR = 1.3, 95% CI = 1.0-1.8) per week compared with women with ≥ 3 hours/week. Adjusted OR for irregular cycles was decreased in women constantly in the lowest tertile of LTPA index in HUNT 1 and HUNT 2 (OR = 0.4, 95% CI = 0.2-0.9). Adjusted OR for prolonged bleeding was 2.6 (95% CI = 1.3-5.4) for women with < 1 hour/week of light LTPA and 2.3 (95% CI = 1.3-4.3) for women with 1-2 hours, compared with ≥ 3 hours/week.

Conclusions: Very low physical activity may increase the risk of menstrual cycle disruptions. Moderate PA should be encouraged for optimum reproductive health.