Physical fitness and activity as separate heart disease risk factors: a meta-analysis

Objective: Public health policies for physical activity presume that the gr eatest health benefits are achieved by increasing physical activity among t he least active. This presumption is based largely on studies of cardioresp iratory fitness. Tn assess whether studies of cardiorespiratory fitness are germane to physical activity :guidelines, we compared the dose-response re lationships between cardiovascular disease endpoints with leisure-time phys ical activity and fitness from published studies. Data Sources: Twenty-thre e ses-specific cohorts of physical activity or fitness (representing 1,325, 004 person-years of follow-lip. cited in Tables 4-1 and 4-2 of the Surgeon General's Report. Data Synthesis: Relative risks were plotted as a function of the cumulative percentages of the samples when ranked from least fit or active, to most fit or active. To combine study results, a weighted averag e of the relative risks over the 16 physical activity or seven fitness coho rts was computed at every 5th percentile between 5 and 100%. The analyses s how that the risks of coronary heart disease or cardiovascular disease decr ease linearly in association with increasing percentiles of physical activi ty. In contrast, there is a precipitous drop in risk occurring before the 2 5th percentile of the fitness distribution. As a consequence of this drop, then is a significant difference in the risk reduction associated with bein g more physically active or physically fit (P less than or equal to 0.04). Conclusions: Being unfit warrants consideration as a risk factor, distinctl y from inactivity. and worthy of screening and intervention. Formulating ph ysical activity recommendations oil the basis of fitness studies may inappr opriately demote the status of physical fitness as a risk factor while exag gerating the public health benefits of moderate amounts of physical activit y.