To the Editor: Dr Sui and colleagues1 studied cardiorespiratory fitness and adiposity as mortality predictors in older adults. I have several questions about this study.
First, other studies have found that physical activity, even with some measurement errors, is associated with cardiovascular fitness with a beneficial association with cardiovascular disease and all-cause mortality.2 - 4 However, in this study, the rates of physical inactivity were virtually identical in survivors and decedents (25%). It is not clear why there would be an association of mortality with low fitness but not with physical inactivity.
Second, rather than enrolling participants within a narrow period of time as the baseline, the Aerobics Center Longitudinal Study is a continuous observational study of patients examined at the Cooper Clinic from 1979 to 2003. Therefore, a simple comparison of baseline values in some variables between decedents and survivors may be misleading. For example, decedents and survivors had similar body mass index measurements (26) (calculated as weight in kilograms divided by height in meters squared). However, hazards ratios for deaths were higher in those with obesity (1.31 for body mass index 30.0-34.9 and 2.29 for body mass index 35 or higher). Patients who visited the Cooper Clinic in the earliest years would be more likely to have died by the time of data analysis because of aging while they also would be more likely to have a low rate of obesity because the prevalence of obesity has substantially increased during the last 3 decades. Adjustment for examination year may not totally eliminate the bias but may reduce it.
Third, an analysis of cardiovascular disease mortality for this group of patients would be informative. Patients with diseases such as tuberculosis, AIDS, and hepatitis B and C may have relatively low fat and low fitness levels. Analysis of the relationship between obesity and cardiovascular disease may be more relevant.
Fourth, it would be valuable to have information about the validity and reliability for the fat measurements.
Financial Disclosures: None reported.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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