Harlow, Sioban D., and Meekyong Park. "A Longitudinal Study of Risk Factors for the Occurrence, Duration, and Severity of Menstrual Cramps in a Cohort of College Women." PSC Research Report No. 95-341. November 1995.
This report describes how women's menstrual cramps vary from cycle to cycle over time. The authors examine the influence of weight and lifestyle factors on occurrence, duration, and severity of menstrual pain. The authors designed a one-year prospective menstrual diary study on 165 women, aged 17-19 years, entering a local university in 1985. They measured the occurrence, length, and maximum severity of pain during a menstrual period as well as missing an activity during a menstrual period. Menstrual pain occurred during 71.6% of observed menstrual bleeds, most commonly beginning the first day of menses. The median duration was two days. Sixty percent of women reported at least one episode of severe pain, while 13 percent reported severe pain more than half the time. Missing an activity, though experienced occasionally by many women, was an infrequent occurrence. Earlier age at menarche and long menstrual periods increased the occurrence, duration, and severity of pain. Smoking did not increase the probability of having pain, but given pain, smokers were more likely to have cramps last longer than two days and to use pain medication. Being overweight was an important risk factor for both the probability of having pain and longer duration of pain. Frequent alcohol consumption decreased the probability of having menstrual cramps, but given pain, increased duration and severity. Physical activity was not associated with any pain parameter. The authors conclude that the occurrence and severity of menstrual cramps is influenced by potentially modifiable host characteristics including weight, smoking, and alcohol consumption.