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Effects of Body Mass Index and Exercise on Risk of Heart Failure
Abstract & Commentary
By Harold L. Karpman, MD, FACC, FACP, Clinical Professor of Medicine, UCLA School of Medicine. Dr. Karpman reports no financial relationship to this field of study.
Synopsis: Evaluation of the clinical course of the 21,094 eligible U.S. male physicians in the Physicians' Health Study revealed that an elevated BMI in both pre-obese and obese subjects was associated with an increased risk of CHF and that vigorous physical activity was associated with a decreased risk of CHF.
Source: Kenchaiah S, et al. Body mass index and vigorous physical activity and the risk of heart failure among men. Circulation 2009;119:44-52.
Excess body weight, sedentary lifestyle, and congestive heart failure (CHF) are recognized major public health problems in the United States and worldwide.1-3 Although BMI in the obese range (≥ 30 kg/m2) has clearly been demonstrated to be associated with an increased risk of CHF, the risk in overweight or pre-obese (25-29.9 kg/m2) individuals has been unclear.4 As a result, the Heart Failure Society of America has recommended that a BMI of < 30 kg/m2 should be the target for all individuals to prevent the development of CHF.5
Although physical activity has been recognized as a key determinant of body weight and an important component of weight reduction and weight maintenance6 and although numerous health benefits of physical activity have been reported,6 the effects of exercise on CHF risk has remained uncertain.7 As a result, Kenchaiah and his colleagues analyzed the impact of overweight or pre-obese status as well as the effects of physical activity on the risk of CHF between 1982 and 2007 in a large prospective cohort of men in the Physicians' Health Study (PHS).8 They analyzed the results in 21,094 men who were participants in the PHS and determined that higher BMI was associated with a greater risk of CHF and that this increased risk occurred in a linear fashion (lean to overweight to obese) without evidence of a threshold and was evident not only in obese, but also in the overweight or pre-obese men. Vigorous physical activity was associated with a graded reduction in the risk of CHF. Lean and active individuals had the lowest risk, whereas obese and inactive individuals had the highest risk of developing CHF.
Published studies have demonstrated a statistically significant increased risk of CHF among obese individuals,4,7 but increased risk had not previously been demonstrated in pre-obese men.4 Kenchaiah's analysis of the PHS data determined that there was a 49% increase in the risk of CHF among overweight men and that vigorous physical activity (defined as exercise to the point of breaking a sweat) performed at least 1-3 times a month conferred a 18% reduction in the risk of CHF.8 Also, elevated BMI was associated with a greater risk of CHF in all subgroups, though its effect was stronger in younger compared with older participants and in nondiabetic compared with diabetic subjects. The beneficial impact of vigorous physical activity was evident in all categories of baseline covariates except among diabetics in whom no association was noted; however, it is important to recognize that diabetics constituted a relatively small sample size in the group. Excess weight may contribute to CHF by altering cardiac structure and function, activating neuroendocrine pathways, predisposing to sleep-disordered breathing, promoting chronic kidney disease, and stimulating the development of atherogenic risk factors such as hypertension, insulin resistance, diabetes mellitus, and dyslipidemia.
The results obtained from the well-run observational PHS study will have to be confirmed by additional carefully controlled studies targeting improvements in BMI and physical activity levels to determine with absolute certainty whether intentional weight reduction to optimal levels in overweight and obese individuals together with improved physical activity would lessen the probability of the occurrence of CHF. For the time being, it should be recognized that in the United States, 37% of the population are pre-obese, 25% are obese, 38% do not achieve the recommended amount of physical activity, and 14% are essentially inactive.1 Since CHF continues to impose substantial morbidity, mortality, and financial costs,2 public health measures to curtail excess weight, maintain optimal weight, and promote regular physical activity are obviously needed to limit the risk of occurrence of CHF in both men and women.
1. Centers for Disease Control and Prevention. United States overweight and obesity prevalence estimates for 2006 and physical activity prevalence estimates for 2007. Available at: www.cdc.gov.
2. Global overweight and obesity estimates for 2005 and physical inactivity: A global public health problem. Geneva, Switzerland: World Health Organization. Available at: www.who.int/en/.
3. Rosamond W, et al. Heart disease and stroke statistics - 2008 update: A report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation 2008;117:e25-e146.
4. Kenchaiah S, et al. Obesity and the risk of heart failure. N Engl J Med 2002;347:305-313.
5. Heart Failure Society of America. HFSA 2006 Comprehensive Heart Failure Practice Guideline. J Card Fail 2006;12:e1-e2.
6. Haskell WL, et al. Physical activity and public health: Updated recommendations for adults from the American College of Sports Medicine and the American Heart Association. Circulation 2007;116:1081-1093.
7. Bahrami H, et al. Novel metabolic risk factors for incident heart failure and their relationship with obesity: The MESA (Multi-Ethnic Study of Atherosclerosis) study. J Am Coll Cardiol 2008;51:1775-1783.
8. Kenchaiah S, et al. Body mass index and vigorous physical activity and the risk of heart failure among men. Circulation 2009;119:44-52.