Obesity, Physical Activity, and Their Interaction in Incident Atrial Fibrillation in Postmenopausal Women
Does physical activity modify the relationship between obesity and atrial fibrillation (AF) in women?
The subjects of this study were 93,676 postmenopausal women (mean age 63.4 years, range 50-79 years) enrolled in the Women’s Health Initiative Observational Study. The intensity and amount of physical activity were assessed with detailed questionnaires and used to calculate metabolic equivalent task (MET) hours/week. Women with AF at baseline were excluded. New cases of AF were identified by serial questionnaires and review of Medicare claims or hospital records.
The prevalence of new AF during a mean follow-up of 11.5 years was 12%. Increasing body mass index was independently associated with higher risk of AF (hazard ratio [HR], 1.12 per 5 kg/m2 increase), as was lower physical activity (HR, 0.9 for 0 versus >9 MET hours/week). Higher levels of physical activity attenuated the increased risk of AF associated with obesity.
The authors concluded that physical activity lowers the risk of AF in postmenopausal women and attenuates the higher risk of AF associated with obesity.
Some studies have reported that strenuous physical activity in athletes is associated with a heightened risk of AF. Although the present study might seem to contradict the prior studies, it is important to note that the degree of physical activity considered strenuous is far less in postmenopausal women than in young athletes. There are several mechanisms by which obesity could promote AF: systemic inflammation, local inflammatory factors in pericardial fat, changes in autonomic tone, and left atrial dilatation. The beneficial effects of exercise on inflammatory factors and autonomic tone might explain why exercise modifies the effect of obesity on risk of AF.
Keywords: Athletes, Inflammation, Body Mass Index, Motor Activity, Dilatation, Atrial Fibrillation, Risk Factors, Hospital Records, Obesity, Metabolic Equivalent, Questionnaires, Medicare
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