than women with regular or short cycles, reported Yi-Xin Wang, PhD, of Harvard TH Chan School of Public Health, Boston, and associates. This is particularly true in the presence of cardiovascular disease and a history of smoking.
In a peer-reviewed observational study of 79,505 premenopausal women enrolled in the Nurses’ Health Study II, the researchers sought to determine whether a life-long history of irregular or long menstrual cycles was associated with premature death. Patients averaged a mean age of 37.7 years and had no history of cardiovascular disease, cancer, or diabetes at enrollment.
Although irregular and long menstrual cycles are common and frequently linked with an increased risk of major chronic diseases – such as ovarian cancer, coronary heart disease, type 2 diabetes, and mental health problems – in women of reproductive age, actual evidence linking irregular or long menstrual cycles with mortality is scant, the researchers noted in the BMJ.
During the study, participants checked in at ages 14-17 years, 18-22 years, and 29-46 years to report the usual length and regularity of their menstrual cycles. Over 24 years of follow-up, a total of 1,975 premature deaths were noted, including 894 from cancer and 172 from cardiovascular disease.
Irregular cycles appear to bring risks
After considering other possible factors of influence, including age, weight, lifestyle, and family medical history, Dr. Wang and associates noted higher rates of mortality among those consistently reporting irregular cycles than women in the same age ranges with very regular cycles. Specifically, women aged 18-22 years and 29-46 years with cycles of 40 days or more were at greater risk of dying prematurely than were those in the same age ranges with cycles of 26-31 days.
Cardiovascular disease was a stronger predictor of death than cancer or other causes. Also included in the higher-risk group were those who currently smoked.
Among women reporting very regular cycles and women reporting always irregular cycles, mortality rates per 1,000 person-years were 1.05 and 1.23 at ages 14-17 years, 1.00 and 1.37 at ages 18-22 years, and 1.00 and 1.68 at ages 29-46 years, respectively.
The study also found that women reporting irregular cycles or no periods had a higher body mass indexes (28.2 vs. 25.0 kg/m2); were more likely to have conditions including hypertension (13.2% vs. 6.2%), high blood cholesterol levels (23.9% vs. 14.9%), hirsutism (8.4%
vs. 1.8%), or endometriosis (5.9% vs. 4.5%); and uterine fibroids (10.0% vs. 7.8%); and a higher prevalence of family history of diabetes (19.4% vs. 15.8%).
Dr. Wang and associates also observed – using multivariable Cox models – a greater risk of premature death across all categories and all age ranges in women with decreasing menstrual cycle regularity. In models that were fully adjusted, cycle lengths that were 40 days or more or too irregular to estimate from ages 18-22 and 29-46 expressed hazard ratios for premature death at the time of follow-up of 1.34 and 1.40, compared with women in the same age ranges reporting cycle lengths of 26-31 days.
Of note, Dr. Wang and colleagues unexpectedly discovered an increased risk of premature death in women who had used contraceptives between 14-17 years. They suggested that a greater number of women self-reporting contraceptive use in adolescence may have been using contraceptives to manage symptoms of polycystic ovary syndrome (PCOS) and other conditions such as endometriosis.
Relying on the potential inaccuracy inherent in patient recall of their menstrual cycle characteristics, and the likelihood for other unmeasured factors, may have affected study results. Study strengths included the significant number of participants who had a high follow-up rate over many years, and the availability of menstrual cycle data at three different points across the reproductive lifespan.
Because the mechanisms underlying these associations are likely related to the disrupted hormonal environment, the study results “emphasize the need for primary care providers to include menstrual cycle characteristics throughout the reproductive life span as additional vital signs in assessing women’s general health status,” Dr. Wang and colleagues cautioned.