- The amount of physical exercise a woman undertakes at any age has no consequence on the timing of her menopause, according to an extensive study
- On the other hand, the study seems to suggest that environmental factors like diet and smoking may play a role in early menopause
There is no association between the amount of physical activity and the risk of early menopause, according to the largest study conducted on this subject.
The study has been published in one of the world's leading reproductive medicine journals, Human Reproduction.
Dr Elizabeth Bertone-Johnson, Professor of Epidemiology at the University of Massachusetts, USA, who directed the research, said: "Our study provides considerable information in helping us understand the relationship between activity and timing of menopause; this is because of its size, its focus on early menopause specifically, and because of its prospective design, which limited the likelihood of bias and allowed us to look at physical activity at different time periods."
StudyThe team analyzed data from 107,275 female United States registered nurses aged 25-42 who enrolled in the Nurses' Health Study II in 1989.
The nurses were followed prospectively until 2011 by asking them to complete questionnaires about lifestyles and medical conditions every two years.
The main questions asked were related to the duration and intensities of recreational physical activities they did - activities involved were walking, running, cycling, racquet sports, swimming laps, aerobic exercises, yoga, weight training and high-intensity activities.
The researchers also gathered information on their age and education, the age of their first period, history of pregnancy, birth control measures and smoking, height and body mass index (BMI), diet and use of dietary supplements, race and ethnicity.
The researchers then multiplied the number of hours per week of each activity by its metabolic equivalent (MET) score to create total MET hours per week. One MET is equivalent to one kilogram calorie per kilogram per hour (kcal/kg/h) that is in turn equal to the amount of energy expended by sitting quietly for an hour.
The results of the 20-year follow-up study showed that 2786 women experienced natural menopause before the age of 45. The results obtained were independent of whether the exercise level of the women was less (less than three MET hours a week of physical activity) or more (42 or more hours a week equal to four or more hours of running or eight or more hours of brisk walking per week).
There was also no association between the amount of physical activity reported in their teenage years and the risk of early menopause.
The first author of the paper, Mingfei Zhao, a graduate student at the University of Massachusetts, said: "While our results do not suggest that more physical activity is associated with lower risk of early menopause, we would encourage premenopausal women to be physically active, as exercise is associated with a range of health benefits, such as a lower risk of heart disease, diabetes, breast cancer and other conditions. Our results in no way suggest that premenopausal women should not be physically active."
Dr Bertone-Johnson said that their work implies a role of environmental factors on early menopause. For example, high intake of calcium and vitamin D from dairy foods, and high intake of vegetable protein (and not animal protein) were associated with a lower risk. On the other hand, cigarette smoking and being underweight are linked to a higher risk. The researchers are still investigating other factors as well that could influence early menopause.
Although women self-reported their physical activity and menopausal status, the fact that the assessment was done repeatedly (every two years) the bias from self-reporting would be negligible. Also, although the majority of the participants were white, the researchers think ethnicity was unlikely to affect the physiological relation between physical activity and menopause.
- Mingfei Zhao, Brian W Whitcomb, Alexandra C Purdue-Smithe, JoAnn E Manson Susan E Hankinson, Bernard A Rosner, Elizabeth R Bertone-Johnson., "Physical activity is not related to risk of early menopause in a large prospective study" Human Reproduction (2018) https://doi.org/10.1093/humrep/dey267