Context

Although levels of physical activity and aerobic capacity decline with age and the prevalence of obesity tends to increase with age, the independent and joint associations among fitness, adiposity, and mortality in older adults have not been adequately examined.

Objective

To determine the association among cardiorespiratory fitness ("fitness"), adiposity, and mortality in older adults.

Design, Setting, and Patients

ohort of 2,603 adults aged 60 years or older (mean age = 64.4 [SD = 4.8] years; 19.8% women) enrolled in the Aerobics Center Longitudinal Study who completed a baseline health examination during 1979-2001. Fitness was assessed by a maximal exercise test, and adiposity was assessed by body mass index (BMI), waist circumference, and percentage body fat. Low fitness was defined as the lowest fifth of the sex-specific distribution of maximal treadmill exercise test duration. The distributions of BMI, waist circumference, and percentage body fat were grouped for analysis according to clinical guidelines.

Main Outcomes Measure

All-cause mortality through December 31, 2003.

Results

Four hundred fifty deaths were reported during a mean follow-up of 12 years and 31,236 person-years of exposure. Death rates per 1,000 person-years, adjusted for age, sex, and examination year were 13.9, 13.3, 18.3, and 31.8 across BMI groups of 18.5-24.9, 25.0-29.9, 30.0-34.9, and >= 35.0, respectively (P = .01 for trend); 13.3 and 18.2 for normal and high waist circumference (>=88 cm in women; >=102 cm in men; P = .004); 13.7 and 14.6 for normal and high percentage body fat (>=30% in women; >=25% in men; P = .51); and 32.6, 16.6, 12.8, 12.3, and 8.1 across incremental fifths of fitness (P < .001 for trend). The association between waist circumference and mortality persisted after further adjustment for smoking, baseline health status, and BMI (P = .02), but not after additional adjustment for fitness (P = .86). Fitness predicted mortality risk after further adjustment for smoking, baseline health, and either BMI, waist circumference, or percentage body fat (P < .001 for trend).

Conclusions

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.

Editor's Comment. This is another set of interesting data from the epidemiologists at the Aerobics Center. In these data, Sui et al attempt to sort out the relationship between fitness and fatness. They used a standard maximal treadmill test to assess physical fitness. While others have attempted to explore this interesting relationship, none have reported data in a sample of older adults. The sample size of 2,603 adults (nearly 20% women) older than 60 years indicates that increased fitness (note, this is not "physical activity," rather physical fitness) is an independent predictor of mortality, even in overweight groups. This means that there is a "mortality advantage" to being more fit, even if you are overweight or obese. There are some other interesting results contained in this article. For example, older adults with a BMI of more than 30.0 had a lower incidence of all-cause mortality than unfit, normal weight, or lean individuals. This article merits close reading by those interested in the associations among physical activity, physical fitness, and mortality.-JLR