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Physical activity and cardiorespiratory fitness as underappreciated modulators of obesity-related risk of sudden cardiac death To the Editor We read with great interest the recent report by Adabag et al.1 Among a large cohort of middle-aged adults (n=14 491 African American and white men and women; 55% female), baseline measures of obesity, including body mass index (BMI), waist circumference and waist-to-hip ratio (WHR), were related to the incidence of sudden cardiac death (SCD, 253 cases) over a 12.6-year follow-up. BMI was indirectly associated with SCD through its adverse effects on cardiovascular risk factors, diabetes and heart disease, whereas abdominal obesity, measured by WHR, appeared to be the strongest predictor of SCD in nonsmokers. In contrast, the relation between measures of obesity and SCD were inconsistent in current smokers, perhaps due to the relatively small number of SCD cases in this population subset. It was suggested that this finding may reflect the ‘obesity paradox.’ Although the ARIC investigators attempted to adjust for potential confounding variables to clarify the impact of obesity per se on SCD, there was no mention of physical activity or cardiorespiratory fitness (CRF), potential mortality modulators in SCD cohorts. Adherence to a regular exercise regimen (≥30 min/day) is strongly and independently associated with a lower risk of SCD in women.2 Numerous previous studies

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have also shown that low fitness is an independent predictor of mortality in normalweight, overweight, and obese men and women, regardless of the risk factor profile.3 Similarly, we reported that CRF was inversely related to the risk of SCD in a populationbased long-term follow-up study.4 Hu et al5 examined whether higher levels of physical activity can counter the elevated risk of death associated with excess adiposity. During a 24-year follow-up of 116 564 women (30–55 years of age) free of known cardiovascular disease and cancer, there were 10 282 deaths. The relative risk of death of lean (BMI

Physical activity and cardiorespiratory fitness as underappreciated modulators of obesity-related risk of sudden cardiac death.

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