Sui and colleagues found that adults over 60 who had higher levels of cardiorespiratory fitness, lived longer than adults who were unfit, independently of their body fat levels.
Scientists have shown that obesity and being physically inactive are strongly linked to higher risk of death in adults, but little was known about the risks in older adults, wrote the researchers.
The researchers looked at the links between cardiorespiratory fitness, measures of body fat (adiposity), and death among 2,603 participants aged 60 and above. The average age of the group was 64.4 years, and nearly 20 per cent were women. They were enrolled in a study called the Aerobics Center Longitudinal Study that lasted from 1979 to 2001.
Participants' fitness levels were measured using a treadmill exercise and body fat was assessed using Body Mass Index (BMI, the ratio of weight to height squared), waist size, and percentage of body fat.
The researchers defined low fitness as the bottom 20 per cent of fitness scores in the treadmill test for each of the male and female groups.
The results showed that:
- 450 of the participants died during the 12 years of follow up (up to December 2003; 31,236 person-years of exposure).
- The participants who died were older, less fit, and had higher cardiovascular risks than those who survived.
- But there were no sginificant differences in body fat measures between those who died and those who survived.
- Men and women with higher fitness levels mostly had fewer cardiovascular risks, eg for hypertension, diabetes, high cholesterol.
- They also had lower rates of death than unfit participants, regardless of body fat, except for two of the obesity categories.
- In most cases, rates of death for the most fit were less than half the rates of death of the unfit.
- Higher fitness was linked to lower risk of death due to all causes.
- This was true in both normal weight and overweight BMI groups, for participants with normal waist size, abdominal obesity, normal per cent body fat, and excessive body fat.
"In this study population, fitness was a significant mortality predictor in older adults, independent of overall or abdominal adiposity."
"Clinicians should consider the importance of preserving functional capacity by recommending regular physical activity for older individuals, normal-weight and overweight alike," they added.
Commenting on the results, the researchers wrote that:
"We observed that fit individuals who were obese (such as those with BMI of 30.0 to 34.9, abdominal obesity, or excessive percent body fat) had a lower risk of all-cause mortality than did unfit, normal-weight, or lean individuals."
"Our data therefore suggest that fitness levels in older individuals influence the association of obesity to mortality," they explained.
They also wrote that the new evidence shed significant light on the complex long term associations among fitness, body size and survival, and suggested it may be possible to bring down death rates due to all causes among older adults, including the obese, by encouraging them to take regular physical exercise.
Even brisk walking for 30 minutes nearly every day (burning about 8 kcal/kg per week) will help to keep most older adults out of the low fitness category, suggested the researchers.
"Enhancing functional capacity also should allow older adults to achieve a healthy lifestyle and to enjoy longer life in better health," they wrote.
"Cardiorespiratory Fitness and Adiposity as Mortality Predictors in Older Adults.
Xuemei Sui; Michael J. LaMonte; James N. Laditka; James W. Hardin; Nancy Chase; Steven P. Hooker; Steven N. Blair.
JAMA 2007 298: 2507-2516
Vol. 298 No. 21, December 5, 2007
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Written by: Catharine Paddock