The researchers suggest that older people who perform frequent and diverse exercise without high intensity can reduce the risk of premature death.
Ying Kuen Cheung, a professor in biostatistics at Columbia University's Mailman School of Public Health in New York, NY, and colleagues report their findings in the Journal of General Internal Medicine.
The team hopes the study will help healthcare providers give better, more specific advice to their older patients on how to stay active and healthy.
According to the American Heart Association, regular exercise has many health benefits for older people.
For example, it can help prevent bone loss and thus reduce the chances of fracture, and it lessens the risk of many aging-related diseases.
Regular exercise also increases muscle strength and can improve balance and coordination, which in turn reduces the risk of falls. It can help older people get up from a chair, do household chores, go out shopping, carry their bags, and generally maintain quality of life and independence.
For their study, Prof. Cheung and colleagues analyzed data on 3,298 stroke-free people from different ethnic groups who took part in the population-based Northern Manhattan Study (NOMAS).
Study looked at dimensions of physical activity
The team wanted to identify which dimensions of leisure-time physical activity might be linked to heart-related premature deaths in older people.
- Over 30 percent of Americans aged 65 and older report no leisure-time physical activity
- Active people with chronic diseases are less likely to die prematurely than inactive people with these conditions
- Older adults can work with healthcare providers to plan activities around limitations.
The authors note that previous studies have mostly used overall measures - such as total energy counts - and not looked at specific dimensions of physical activity, such as frequency, variety, and intensity of exercise.
The NOMAS data includes information that helps to evaluate medical, socioeconomic and other risk factors relevant to heart health in a group of people with no history of stroke.
The average age of the participants when they signed up to the study during 1993-2001 was 69 years.
After enrollment, they took part in yearly telephone interviews. The median follow-up was 17 years.
Every year, the participants answered questions about general health, plus frequency, intensity, and types of leisure time physical activity.
Examples of activity included walking, jogging, cycling, gardening, yard work, aerobics, water sports, tennis, golf, and squash.
Frequent, varied, but not intense
From the data, the researchers were able to assess frequency, variety, and intensity of physical activity, and compare them with heart-related and non-specific deaths. For exercise intensity, they used a measure called energy-to-duration ratio (EDR).
The analysis found that higher frequency of activity was linked to reduced rates of heart-related deaths, but it showed no link to non-heart-related deaths.
It also showed higher variety of activity (high number of activity types) appeared to be beneficial in protecting against death from any cause.
However, the team found a high EDR - frequent bouts of high intensity exercise - was linked to higher risk of heart-related deaths.
"Performing frequent and diverse exercise without high intensity in an elderly population such as ours is achievable and can reduce the risk of death," says Prof. Cheung.
He says taking part in a large number of different activities can be more strongly linked to cardio-respiratory fitness. This could explain why they found variety of exercise appeared to have a protective effect across the board.
"Our findings thus suggest that high frequency of high intensity exercise may undo the benefits of frequent exercise in terms of cardiovascular mortality. Given the ease of participating in low intensity but daily leisure time physical activity, our findings suggest that this can be incorporated in current recommendations provided to older people."
Prof. Ying Kuen Cheung