Discoveries
Behind the Findings: Why Do Women Gain More Benefit From Exercise Than Men?
Women tend to spend less time exercising than men do, even though public health officials recommend the same amount and intensity of physical activity each week for both sexes. However, new research from the Smidt Heart Institute at Cedars-Sinai suggests that women benefit disproportionately from regular exercise.
The study, published in the Journal of the American College of Cardiology, found that women only need to exercise about two and a half hours per week to obtain the same survival benefits that men achieve with five hours of exercise per week. The findings add evidence to the growing body of literature revealing fundamental and consequential physiological differences between the sexes.
Here, Smidt Heart Institute physician-leaders analyze the salient takeaways of their study in a roundtable discussion.
Director of Cardiovascular Population Sciences, Director of Public Health Research, Director of the Institute for Research on Healthy Aging, and the Erika J. Glazer Chair in Women’s Cardiovascular Health and Population Science
Director of Clinical Analytics and Associate Director of the Coronary Intensive Care Unit
Director of Preventive Cardiology, Associate Director of the Preventive and Rehabilitative Cardiac Center, Associate Director of the Barbra Streisand Women’s Heart Center, and the Anita Dann Friedman Chair in Women’s Cardiovascular Medicine and Research
Associate Medical Director of the Biomedical Imaging Research Institute
The public health message should be that everyone benefits from exercise and a small amount goes far in terms of a reduction in mortality. For women, finally we have some good news: You benefit a little more for every minute of exercise compared with men!”
— Dr. Martha Gulati
Men and women both achieved substantial reductions in all-cause and cardiovascular mortality with almost any level of exercise. How might unmeasured factors have played a role in the finding that women consistently obtained a greater survival benefit than men from the same amount of physical activity?
Martha Gulati, MD: Women at every age group report less physical activity than men, but it may be that they are being active and just not calling it “exercise.” It is really hard to know how much nonleisure activity may confound the results. Women do tend to take on more household responsibilities and caregiving duties for children and older parents, which may add up to a lot of unmeasured physical work.
Susan Cheng, MD: One of the reviewers for the article actually raised this issue of accuracy in measurement, and it turns out that, on average, women tend to underreport their exercise more than men. So, we did a secondary analysis accounting for this, and we still saw these interesting differences. We also adjusted for many known important covariates, such as age, whether someone smokes or has other comorbidities, and socioeconomic factors. There is potential for confounding—we cannot capture everything that happens in real life—but we were pretty compelled by the decreased mortality signal.
Alan Kwan, MD: The fact that women continue to benefit with additional exercise, whereas effects in men top out at a lower level, also suggests that there may be real physiological differences that are not just artifacts of the data.
Dr. Gulati authored the groundbreaking 2005 New England Journal of Medicine paper that redefined cardiac fitness and heart rate measures for women. What other important physiological differences between the sexes have emerged in cardiology since then?
AK: From an imaging standpoint, there are baseline differences between men and women in cardiovascular anatomy, the way our bodies react to aging and how we react to exercise. For example, women typically have smaller hearts and blood vessels, even when accounting for body size. As women age or exercise, the heart remodels differently, especially in terms of wall thickness and chamber size.
SC: We also see this dose-response relationship where women experience a comparatively beneficial effect from exercise. Unfortunately, other publications have reported the converse, where the same number of cardiometabolic risk factors in men versus women as they age results in differential trajectories of elevated blood pressure, with women getting the short end of the stick.
MG: Previous work showed that the fitness level of women was always lower than that of men when matched by age and that age-predicted fitness level is associated with mortality. Even the type of physical exercise affects our fitness level, and that may be playing out in the overall survival benefit observed in this study.
Joseph Ebinger, MD: We are so used to looking at static measures of strength and exercise capacity. For example, studies have shown that, in general, men tend to have higher lean muscle mass at the start of identical exercise programs. But when you look at changes over time, women will gain a relatively larger amount of muscle mass than men, and women have a relatively larger vasodilatory pattern. All of this indicates that, at a physiological level, the body responds differently between the two groups.
What other information is needed before exercise guidelines should be updated?
SC: Some current exercise recommendations are based on soft data. There is certainly an opportunity to improve upon the evidence base with new sets of studies like this one.
MG: Whenever we have guidelines that recommend the exact same thing for men and women, we should always question whether they are based on evidence. The public health message should be that everyone benefits from exercise and a small amount goes far in terms of a reduction in mortality. For women, finally we have some good news: You benefit a little more for every minute of exercise compared with men!
JE: As for changing guidelines, it is always best to have prospective results , but that would take a generation to gather. Continued work should further subcategorize who is going to benefit and by how much. It should also clarify what drives these differences. at the cellular and molecular levels That is going to be really important for convincing the broader medical community that there really is variation in how men and women experience and benefit from exercise.
SC: We encourage other investigators to look for similar findings in large datasets. If they obtain the same findings, the guideline committees could then decide on formal updates.
How can clinicians use these findings to improve the state of research and clinical care regarding the benefits of exercise?
AK: We need to emphasize this important message, and not just in doctor visits. People should find physical activity they enjoy that gets them moving to help improve heart health. This applies even to patients who already have coronary artery disease or are recovering from a heart attack, who are often afraid of starting activity. Through resources like our Cardiac Rehabilitation Program, we can help them start exercising in a safe and monitored setting.
JE: When we look at the age-stratified component of the study’s findings, really the biggest survival benefit comes in midlife. So it is important not to wait until you start to see adverse effects of inactivity. We need to encourage people to start exercising early in life.
MG: The one big, overarching takeaway is that we should always be looking for sex differences, because we know that there are biological differences between men and women. Women are highly understudied in so much of our cardiovascular field.
