By CAFMI From JAMA
Prevalence of Low Cardiorespiratory Fitness in US Youth and Adults
Low cardiorespiratory fitness (CRF) is recognized as a significant risk factor for cardiovascular disease (CVD) in adults, yet detailed data on its prevalence among adolescents and adults has been limited until recently. A comprehensive cross-sectional study utilizing the National Health and Nutrition Examination Survey (NHANES) data from 1999 to 2002 examined CRF levels in a representative sample of 3896 adolescents aged 12 to 19 and 4982 adults aged 20 to 49. CRF was estimated through a submaximal treadmill exercise test, focusing on those falling in the lowest 20th percentile of estimated maximal oxygen consumption (VO2 max), thus classified as having low fitness. The study revealed that approximately 40.4% of adolescents and 41.5% of adults in the United States have low CRF, indicating a substantial portion of the population may be at increased risk for cardiovascular conditions.
Associations Between Low Fitness and Cardiovascular Risk Factors
The findings further revealed strong correlations between low CRF and several established cardiovascular risk factors. Among adolescents, low fitness was markedly associated with obesity, showing an odds ratio (OR) of 3.5, indicating these individuals were 3.5 times more likely to be obese compared to their fitter peers. Additional associations included hypertension (OR 2.0) and elevated triglycerides (OR 2.0). In adults, low CRF correlated with obesity (OR 3.4), hypertension (OR 2.2), dyslipidemia (OR 1.7), diabetes (OR 1.9), and smoking (OR 1.3). These associations highlight that low fitness is not only prevalent but also tightly linked with multiple cardiovascular risk factors across age groups, which can compound to increase the likelihood of developing heart disease over time.
Clinical Implications and Call for Early Intervention
For primary care clinicians, these findings underscore the importance of assessing fitness levels as part of routine health evaluations, especially in younger patients who may exhibit early risk factors. Given the high prevalence of low CRF in both adolescents and adults, early lifestyle interventions promoting physical activity could have substantial benefits in reducing future CVD risk. Strategies might include counseling for physical activity, weight management, smoking cessation, and regular monitoring of blood pressure and lipid levels. Early identification and management of low CRF and its associated risk factors can contribute significantly to preventing the progression of cardiovascular disease and improving long-term patient outcomes.
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