Exercise May Shield Older Women From Afib

High-intensity exercise was tied to a reduced risk for atrial fibrillation in postmenopausal women and obese women in particular, researchers said.

According to an analysis of data from the Women's Health Initiative (WHI), women, ages 50 and up, engaging in 3 to 9 and more than 9 metabolic equivalent-hours (MET-hour) per week of physical activity had a 6% and 10% lower risk of atrial fibrillation, respectively, compared with sedentary participants, according to Marco Perez, MD, of Stanford University in Stanford, Calif., and colleagues.

Higher levels of physical activity reduced the risk conferred by obesity (P=0.033 for interaction), they wrote in the Journal of the American Heart Association.

The group also found that those who did more than 15 MET-hour per week of strenuous activity had a significant 9% reduction in atrial fibrillation risk.

In addition, increased body mass index (BMI) and reduced physical activity were independently associated with higher rates of the heart rhythm disorder after multivariate adjustment, they said.

Obesity is a well recognized risk factor for atrial fibrillation (AF), but Perez told MedPage Today that the impact of physical exercise on atrial fibrillation risk associated with obesity has not been widely studied in higher-risk populations such as postmenopausal women.

Action Points Note that this analysis of the Women's Health Initiative found a link between higher body mass index and new-onset atrial fibrillation. Be aware that regular exercise decreased the risk of atrial fibrillation, particularly among overweight and obese women.

"The nature of the association between higher physical activity levels and Afib risk is controversial," the researcher wrote. "Several studies have reported that strenuous physical activity is associated with increased risk of Afib." But those studies were done in mostly healthy young athletes or middle-age men with few cardiovascular risk factors who later developed atrial fibrillation, they added.

"If physical activity reduces the risk of Afib conferred by obesity in older women, it may have important implications for the primary prevention of Afib in this vulnerable population," the researchers wrote.

Study Details

The WHI was a prospective, observation study that included 93,676 postmenopausal women, ages 50 to 79, who were followed for an average 11.5 years. All the women were enrolled between 1994 and 1998.

Current study participants were excluded if they had an atrial fibrillation diagnosis at enrollment, had missing data, or were underweight. The final analysis by Perez and colleagues was done in 81,317 women.

Incident atrial fibrillation was identified using WHI-ascertained hospitalization records and diagnostic codes from Medicare claims. A multivariate Cox hazard regression model adjusted for demographic and clinical risk factors was used to evaluate the interaction between obesity and physical activity, and its association with incident atrial fibrillation.