Public Release: 

Brisk walking/physical activity of similar intensity may lower risk of death among older women

New study finds larger health benefit from physical activity than previously reported

Brigham and Women's Hospital

Boston, MA-- Lack of exercise or physical activity is estimated to cause as many deaths each year as smoking. Current guidelines recommend at least 150 minutes a week of moderate intensity physical activity, or 75 minutes a week of vigorous-intensity aerobic physical activity (or a combination of the two), and muscle-strengthening exercises two or more days a week.

A new study led by investigators at Brigham and Women's Hospital published in Circulation on November 6, 2017, investigated physical activity of women measured over seven days using a wearable device called a triaxial accelerometer, and found that more physical activity and higher intensities of physical activity could decrease the risk of death in older women from any cause. Moderate to vigorous intensity physical activity (e.g. brisk walking) was associated with 60-70 percent lower risk of death at the end of the four-year study among the most active women, compared to the least active.

"The fact the physical activity lowers mortality rate is nothing new - we have many studies showing this. However, previous studies have primarily relied on self-reported physical activity, and self-reports tend to be imprecise. Based on these self-report studies, we know that physical activity is associated with a 20-30 percent reduction in mortality rates, comparing the most with the least active. Using device-measured physical activity in the present study, we observed a 60- 70 percent risk reduction larger than previously estimated from self-report studies. For context, non-smokers have about a 50 percent reduction, compared with smokers," stated I-Min Lee, MBBS, ScD, associate epidemiologist at Brigham and Women's Hospital, and first author of the study. "This study supports current guidelines for physical activity, such as those from the federal government and the American Heart Association, that emphasize moderate-intensity physical activity. It also adds to existing evidence that can inform upcoming physical activity guidelines over time."

This is one of the first studies to investigate physical activity, and a clinical outcome, using the newer generation triaxial wearable devices which have increased sensitivity to recognize physical activity and are capable of more precise measurements than the previously used uniaxial devices, or studies relying on self-reports only.

"We used devices to better measure not only higher intensity physical activities, but also lower intensity activities and sedentary behavior, which has become of great interest in the last few years," stated I-Min Lee, MBBS, ScD.

Data were analyzed from 16,741 participants (average age 72) from the Women's Health Study who wore the device for at least 10 hours a day, on at least four out of seven days.

Light physical activity, such as slow walking, was not associated with lower death rate during the study. Researchers note that light activity may be beneficial for other health outcomes not reported in this paper. Researchers are continuing this study to examine other health outcomes and to examine details of how much and what kinds of activity are healthful.

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The study is supported by National Institutes of Health grants CA154647, CA047988, CA182913, HL043851, HL080467, and HL099355.

Brigham and Women's Hospital (BWH) is a 793-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare. BWH has more than 4.2 million annual patient visits and nearly 46,000 inpatient stays, is the largest birthing center in Massachusetts and employs nearly 16,000 people. The Brigham's medical preeminence dates back to 1832, and today that rich history in clinical care is coupled with its national leadership in patient care, quality improvement and patient safety initiatives, and its dedication to research, innovation, community engagement and educating and training the next generation of health care professionals. Through investigation and discovery conducted at its Brigham Research Institute (BRI), BWH is an international leader in basic, clinical and translational research on human diseases, more than 3,000 researchers, including physician-investigators and renowned biomedical scientists and faculty supported by nearly $666 million in funding. For the last 25 years, BWH ranked second in research funding from the National Institutes of Health (NIH) among independent hospitals. BWH is also home to major landmark epidemiologic population studies, including the Nurses' and Physicians' Health Studies and the Women's Health Initiative as well as the TIMI Study Group, one of the premier cardiovascular clinical trials groups. For more information, resources and to follow us on social media, please visit BWH's online newsroom.

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