Recent guidelines for treatment of overweight and obesity include recommendations
for risk stratification by disease conditions and cardiovascular disease (CVD) risk
factors, but the role of physical inactivity is not prominent in these recommendations.
To quantify the influence of low cardiorespiratory fitness, an objective marker of
physical inactivity, on CVD and all-cause mortality in normal-weight, overweight,
and obese men and compare low fitness with other mortality predictors.
Prospective observational data from the Aerobics Center Longitudinal Study.
Preventive medicine clinic in Dallas, Tex.
A total of 25714 adult men (average age, 43.8 years [SD, 10.1 years]) who received
a medical examination during 1970 to 1993, with mortality follow-up to December 31,
1994.
Cardiovascular disease and all-cause mortality based on mortality predictors (baseline
CVD, type 2 diabetes mellitus, high serum cholesterol level, hypertension, current
cigarette smoking, and low cardiorespiratory fitness) stratified by body mass index.
During the study period, there were 1025 deaths (439 due to CVD) during 258781 man-years
of follow-up. Overweight and obese men with baseline CVD or CVD risk factors were
at higher risk for all-cause and CVD mortality compared with normal-weight men without
these predictors. Using normal-weight men without CVD as the referent, the strongest
predictor of CVD death in obese men was baseline CVD (age- and examination year-adjusted
relative risk [RR], 14.0; 95% confidence interval [CI], 9.4-20.8); RRs for obese men
with diabetes mellitus, high cholesterol, hypertension, smoking, and low fitness were
similar and ranged from 4.4 (95% CI, 2.7-7.1) for smoking to 5.0 (95% CI, 3.6-7.0)
for low fitness. Relative risks for all-cause mortality in obese men ranged from 2.3
(95% CI, 1.7-2.9) for men with hypertension to 4.7 (95% CI, 3.6-6.1) for those with
CVD at baseline. Relative risk for all-cause mortality in obese men with low fitness
was 3.1 (95% CI, 2.5-3.8) and in obese men with diabetes mellitus 3.1 (95% CI, 2.3-4.2)
and as slightly higher than the RRs for obese men who smoked or had high cholesterol
levels. Low fitness was an independent predictor of mortality in all body mass index
groups after adjustment for other mortality predictors. Approximately 50% (n = 1674)
of obese men had low fitness, which led to a population-attributable risk of 39% for
CVD mortality and 44% for all-cause mortality. Baseline CVD had population attributable
risks of 51% and 27% for CVD and all-cause mortality, respectively.
In this analysis, low cardiorespiratory fitness was a strong and independent predictor
of CVD and all-cause mortality and of comparable importance with that of diabetes
mellitus and other CVD risk factors.