Intense Exercise Tied to 65% Lower Death Risk in Older Women

Marlene Busko

November 08, 2017

BOSTON, MA — Older women who engaged in the greatest amount of moderate to vigorous physical activity, such as brisk walking, were found to have a 65% lower risk of all-cause mortality compared with women who performed the least amount of such exercise, a new study reports[1].

The researchers examined women in their early 70s in the Women's Health Study (WHS) who wore a triaxial accelerometer for 7 days to measure physical activity. The findings, by Dr I-Min Lee (Brigham and Women's Hospital, Boston, MA) and colleagues, were published November 6, 2017 in Circulation.

It's been known for a long time that physical activity is associated with lower mortality rates, Dr Lee told theheart.org | Medscape Cardiology. However, "what's really interesting and important to me is the size of this risk reduction," she said.

In previous studies based on self-reports, people who reported they engaged in at least 150 minutes of moderate to vigorous physical activity a week—as recommended by the guidelines—had a 10% to 30% lower risk of short-term death. In comparison, nonsmokers have a 50% lower risk of this outcome than smokers.

Now that physical activity can be better measured using a research-grade triaxial accelerometer, the magnitude of the reduced risk of short-term death with recommended amounts of moderate to vigorous physical activity can be seen to be as strong as not smoking, Lee said.

"Many physicians are not recommending physical activity to their patients," she noted, but the current findings "reinforce that they should dutifully do this every opportunity they get, because . . . this is as strong a protective factor as not smoking."

This study "reinforces the message that adults should strive to meet physical activity guidelines of 150 minutes of moderate or 75 minutes of vigorous exercise per week," Dr Alpa Patel (American Cancer Society, Atlanta, Georgia) who recently published a related article that showed benefits from walking[2] told theheart.org | Medscape Cardiology.

The current study highlights "the consistency in the inverse relationship between volume of moderate or vigorous physical activity with lower risk of death, in a setting where the physical activity is objectively measured."

Sensitive Accelerometers to Detect Movement

Current guidelines for physical activity are primarily based on studies of self-reported moderate to vigorous physical activity, Lee and colleagues write.

They aimed to examine how time spent in sedentary behavior, light physical activity, and moderate to vigorous physical activity measured with a sensitive accelerometer correlated with short-term all-cause mortality in women in the Women's Health Study.

From 2011 to 2015, 18,289 of 29,494 living women (63%) in the Women's Health Study agreed to participate in the current study. Participants were younger and healthier than nonparticipants.

The researchers excluded women who could not walk unassisted outside the home. The remaining 17,708 women were mailed a research-grade triaxial accelerometer (ActiGraph GT3X+, ActiGraph Corp) and asked to wear it on their hips for 7 days (but to take it off when sleeping or swimming) and then mail it back.

This device measures acceleration on 3 planes―up and down, side to side, and front to back―so it is sensitive for picking up small movements, Lee explained. The Fitbit uses similar technology.

The women spent a median of 8.4, 5.8, and 0.5 hours/day being sedentary, doing light physical activity, and doing moderate to vigorous physical activity, respectively.

"The least active quartile were doing 8 minutes a day of moderate to vigorous . . . physical activity," Lee said, which was typically "brisk walking, anything that gets your heart rate up a little bit, gets you to sweat a little bit." The most active quartile did about 68 minutes/day of moderate to vigorous physical activity.

During an average follow-up of 2.3 years, 207 women died.

The total amount of physical activity was inversely related to the risk of all-cause mortality during follow-up, after adjustment for age and time spent wearing the device (model 1, P=0.002).

The relationship was still significant after further adjustment for smoking; alcohol; intakes of saturated fat, fiber, fruits, and vegetables; hormone therapy; parental history of MI; family history of cancer; general health; history of cardiovascular disease; history of cancer; and cancer screening (model 2, P=0.0002).

Compared with women in the lowest quartile of moderate to vigorous physical activity, those in the highest quartile had a 65% lower risk of death during follow-up (HR 0.35; 95% CI 0.20–0.61) in the fully adjusted model.

Light physical activity was inversely associated with risk of death during follow-up after adjustment for age and time spent wearing the device, but the risk was no longer significant after adjustment for the other confounders.

Similarly, increased sedentary behavior was associated with an increased risk of death, but not after adjustment for the confounders in model 2.

Although this study does not support increasing light physical activity or reducing sedentary physical activity, light physical activity may become helpful "as these women grow older" and may be good for their overall function, mental health, and quality of life, Lee said; the researchers are currently studying this possibility.

She would like to see the study replicated in men and in minority women, since these were mainly white women.

In the meantime, the study supports current guidelines, and physicians can advise their patients that "whatever it is you are doing, whether you are walking or playing with your grandchildren or walking the dog, if you can still talk to someone but you cannot sing, that's moderate intensity, so it gives you some idea of how hard you are working."

The study was supported by grants from the National Institutes of Health. The authors have disclosed no relevant financial relationships.

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