Exercise Intensity Not Linked To Mortality Risk In Older Adults

Harder workouts won't cut older lives short, a new study finds.

In an analysis of data from more than 1,500 seniors randomly assigned to moderate or intense exercise for 5 years, or to a control group, researchers found that intense exercise did not raise the risk of mortality, according to the report published in The BMJ.

"This is the first randomized, controlled study examining the long-term aerobic exercise on all-cause mortality compared to controls being asked to follow the physical activity guidelines in a general population of older adults," said study coauthor Ulrik Wisloff, a professor in exercise physiology at the Cardiac Exercise Research Group at The Norwegian University of Science and Technology in Trondheim, Norway.

"Importantly, our data demonstrate larger health benefits in those that undertook mainly high intensity exercise compared to those that mainly undertook exercise with moderate intensity," Wisloff said in an email. "We therefore suggest that future guidelines for physical activity, at least for older adults, should be more specific in requiring at least part of the physical activity should be performed with high intensity."

To look at the impact of exercise intensity on mortality, Wisloff and his colleagues asked all inhabitants of Trondheim, Norway, who were aged 70 to 77 to participate in their study. The researchers excluded seniors if they had uncontrolled hypertension (untreated systolic blood pressure >220 mmHg or diastolic blood pressure >110 mmHg); symptomatic valvular disease; hypertrophic cardiomyopathy; unstable angina pectoris; primary pulmonary hypertension; heart failure; severe arrhythmia; diagnosed dementia; cancer that made participation impossible; chronic communicable infectious diseases, illness, or disabilities that precluded exercise; or participation in other exercise trials.

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Ultimately, 1,567 Trondheimians (790 women) were included at baseline screening and invited for follow-up screening after one, three and five years. In total, 87.5% reported good overall health and 80% reported a medium or high level of physical exercise.

Participants were randomly assigned to high intensity, moderate intensity or to follow the Norwegian guidelines for physical activity (the control group), which meant 400 would participate in two weekly sessions of high intensity interval training (HIIT), 387 would engage in moderate intensity continuous training (MICT) and 780 would follow the Norwegian guidelines for five years.

The average exercise intensity during supervised HIIT and MICT was 90% and 72% of peak heart rate, respectively.

After 5 years, the overall mortality rate was 4.6% (72 participants). That rate "was only half of what was predicted overall in the general population during the study period," Wisloff said.

When the researchers compared the three groups, they found no difference in all-cause mortality between the control group and the HIIT and the MICT group. They also found no differences in cardiovascular disease or cancer between the control group and the combined HIIT and MICT group.

There were hints, however, that the HIIT group was healthier at the end of 5 years.

At that point, there was a non-significant 1.7% absolute risk reduction in all-cause mortality in the HIIT group compared to the control group and a 2.9% absolute risk reduction in all-cause mortality in the HIIT group compared to the MICT group. Peak oxygen uptake after one, three and five years was higher in the MICT and HIIT combined group compared to the control group.

The new study is "unique in that the length of follow-up is longer than most randomized controlled trials," said Nancy Glynn, an associate professor of epidemiology at the University of Pittsburgh Graduate School of Public Health who specializes in physical activity epidemiology with a focus on older adults.

"It would have been valuable for (the researchers) to present intermediate outcomes, such as whether physical function improved over time by intervention type," Glynn said in an email.

The Norwegians in the study might not be comparable to the average American, Glynn said.

"I was struck by the high self-reported activity levels of this population, with less than 10% of their participants engaging in physical activity once a week or less at baseline, compared to national U.S. data that indicate 32% of adults age 65 and older reported no leisure time physical activity in the past month."

—Linda Carroll

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