Marlene Busko

March 07, 2016

PHOENIX, AZ — Postmenopausal women in the Women's Health Initiative who had a first MI and increased or maintained recommended levels of physical fitness and walking had a reduced risk of dying during an 8-year follow-up, in a new study[1].

Importantly, becoming more sedentary was also linked to a greater risk of dying during follow-up, Dr Anna M Gorczyca (Indiana University, Bloomington) reported at the recent American Heart Association (AHA) Epidemiology and Prevention and Lifestyle and Cardiometabolic Health (EPI/Lifestyle) 2016 Scientific Sessions.

Specifically, among the women who sat for less than 8 hours a day before their MI, every 1-hour/day increase in sitting time after their MI was associated with an 11% greater likelihood of dying during follow-up.

"We have known about the beneficial effects of cardiac rehab for years, but this study now adds information about sitting time," Gorczyca told heartwire from Medscape. The message for cardiologists is to encourage patients, especially those who are the least active, to get off the couch. "If patients can reduce their sitting time after an MI and get up and move and even replace it with light to moderate physical activity, we're really seeing beneficial effects," she said.

Session comoderator Dr Marie-France Hivert (Harvard Pilgrim Health Care Institute, Boston, MA) agreed. Instead of telling patients to "aim for 150 minutes of physical activity a week," clinicians should advise them to "just do a little bit; buy yourself a device to increase your physical activity a little bit," which would help get their heart rates up.

Sitting or Walking and Moving After a Heart Attack

Women are still 36% less likely than men to participate in cardiac rehabilitation after a first MI, Gorczyca noted. The researchers aimed to investigate how changes in physical activity, walking, and sitting, before vs after a heart attack affect survival.

They analyzed data from the Women's Health initiative, which enrolled 93,676 postmenopausal women who were 50 to 79 years old during 1994 to 1998 and followed them until 2014.

At baseline and each year until year 8, the women replied to questionnaires that asked about their walking and light, moderate, or strenuous physical activity. At baseline, year 3, and year 6, they also reported how many hours a day they usually spent sitting (while working, eating, watching television, driving or riding in a car, or talking).

From this, the researchers calculated metabolic equivalent [MET] hours/week for physical activity and walking. Being physically active was defined as doing at least 7.5 MET hours of physical activity a week (which corresponds to the current recommendations of at least 150 minutes of moderate/intensive activity a week). A high amount of walking was defined as more than 3.5 MET hours a week. A high sitting time was defined as sitting at least 8 hours a day.

The researchers examined the differences in these measures based on the questionnaire replies immediately before and after the MI.

Of the 3129 women who had a first MI during follow-up, 838 women had data about their physical activity and walking, and 514 women had data about sedentary time.

At baseline, the women with physical-activity data had a mean age of 67 and typically sat for 7.3 hours a day. Most women (306) were inactive before and after their MI; 118 went from being active to inactive; 120 went from being inactive to active; and 294 were active at both times.

Women who went from being inactive to active had a 57% lower risk of all-cause mortality, an 83% lower risk of CHD mortality, and a 67% lower risk of CVD mortality during follow-up, compared with women with consistently low levels of walking.

Similarly, women who went from low to high levels of walking had a 49% lower risk of all-cause mortality, an 88% lower risk of CHD mortality, and a 78% lower risk of CVD during follow-up, compared with women with consistently low levels of walking.

However, women who went from low to high levels of sitting did not have significantly increased survival, compared with those who remained highly sedentary.

But diving deeper revealed that among women who were not highly sedentary before their MI, each increase in hours spent sitting upped their mortality risk (HR 1.11; 95% CI 1.01–1.23).

Similarly, women who went from inactive to active had a 6% lower risk of all-cause mortality for each MET-hour/week increase in physical activity after their MI (HR 0.94; 95% CI 0.91–0.97).

And women who went from a low to high level of walking had a 13% lower risk of all-cause mortality for each MET-hour/week increase in walking after their MI (HR 0.87; 95% CI 0.80–0.95).

Although the study adjusted for confounders, women who were more sedentary after a heart attack may have been sicker, Gorczyca acknowledged. They plan to see whether their findings are confirmed in men and verified using an activity tracker.

Gorczyca has no relevant financial relationships. Disclosures for the coauthors are listed in the abstract.


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