Exercise Lowers Risk of AF in Older, Obese Women

In a recent report published in the Journal of the American Heart Association, Azarbal and colleagues from Stanford University were able to identify exercise as a modifiable risk factor for the development of atrial fibrillation (AF) in 93,676 postmenopausal women followed for 11.5 years.

In this prospective observational substudy of the Women’s Health Initiative, subjects were excluded if they had preexisting AF, incomplete data, or low BMI, leaving 81,317 in the final study sample. Incident AF developed in 12% of these women (≈1.1% per year) over the duration of follow-up, as assessed by WHI-ascertained hospitalization records and diagnostic codes from Medicare claims. Physical activity was assessed at study enrollment by self-reported questionnaires. This cohort had a mean age of 63.4 years, 25.1% were obese, 3.9% had diabetes, and 42.6% had hypertension. Hispanic and African American women were underrepresented (3.6% and 7.8%, respectively).

After adjusting for other risk predictors (including age and race) as well as level of physical activity, increased BMI (per 5 kg/m² increase) was associated with a 12% increased hazard ratio (HR) for incident AF (95% CI, 1.10-1.14) compared with normal BMI; the highest strata of physical activity (more than 9 MET hours/week) was associated with a 10% lower HR for incident AF (95% CI, 0.85-0.96) compared with sedentary women. Increased physical activity favorably modulated the increased risk associated with obesity (interaction P=.033). The increased risk associated with obesity was highest in younger, diabetic women.

As the incidence of AF continues to increase, the importance of attention focused on modifiable risk factors will increase as well. In this relatively young cohort, there was a 1.1% risk of AF annually. Primary care physicians are confronted every day by obesity and inactivity-conjoined and stubborn behavioral/medical barriers to wellness-that each confer independent risk for incident AF. They are, however, modifiable.

This study demonstrates that: (1) physical activity is associated with lower incidence of AF and (2) the increased risk associated with obesity can be attenuated with an increase in physical activity. Education and counseling are essential for sedentary overweight or obese women, in whom the risk for AF may be compounded by the presence of multiple other independent risk factors for the arrhythmia (eg, hypertension, diabetes, sleep apnea). Whether physical activity modifies the risk for AF associated with some of these other comorbidities remains to be explored in future studies. But for now, one word sums it up best: Exercise!

References:

Azarbal F, Stefanick ML, Salmoirago-Blotcher E, et al.  Obesity, physical activity, and their interaction in incident atrial fibrillation in postmenopausal women.J Am Heart Assoc. 2014;3:e001127.