Los Angeles—The conventional wisdom has long been that men are at greater risk for developing AFib than women. Now, a new study taking height into consideration finds the reality is just the opposite: Women actually have a 50% higher risk of developing abnormal heart rhythm disturbance when compared with men.

Authors of the report in the Journal of the American Medical Associate Cardiology emphasized that early interventions and prevention of AFib should be a priority for both female and male patients.

“This is the first study to show an actual flip in the risk of atrial fibrillation,” stated senior author, Christine Albert, MD, MPH, chair of the Department of Cardiology in the Smidt Heart Institute at Cedars-Sinai in Los Angeles. “In this population of 25,000 individuals without prior heart disease, after adjusting for differences in height, women were at higher risk for developing AF [AFib] than their male counterparts—upward of 50%.”

Dr. Albert pointed out that risk for AFib increases with height. Women have been previously seen as having lower risk because they tend to be shorter than men, when in actuality, they only have lower incidence.

“Our study, however, surprisingly suggests that if a man and a woman have the same height, the woman would be more likely to develop AFib,” Dr. Albert noted. “Now the question has changed: Instead of why women are protected, now we must seek to understand why women are at a higher risk.”

The study sought to examine sex differences in AFib incidence and whether risk factors differ by sex in a contemporary cohort of men and women without prevalent cardiovascular disease (CVD).

To determine that, the study team conducted a prospective, cohort analysis within the Vitamin D and Omega-3 Trial (VITAL) Rhythm Study—a randomized trial that examined the effect of vitamin D and omega-3 fatty acid supplementation on incident AFib among men aged 50 years or older and women aged 55 years or older without a prior history of prevalent AF, CVD, or cancer at baseline. Data were analyzed from September 29, 2020, to June 29, 2021.

Taken into consideration were sex, height, weight, BMI, body surface area (BSA), and other AFib risk factors at study enrollment. The researchers were looking for incident AFib as confirmed by medical record review.

The study included 25,229 participants (51% women) with a mean age of 67 years.

The researchers found that—over a median (IQR) follow-up of 5.3 (5.1-5.7) years—900 confirmed incident AFib events occurred among 12,362 men (495 events, 4.0%) and 12,757 women (405 events, 3.2%). After adjusting for age and treatment assignment, the study team determined that women were at lower risk for incident AFib than men (hazard ratio [HR], 0.68; 95% CI, 0.59-0.77; P <.001).

The inverse association between female sex and AFib persisted after adjustment for race, ethnicity, smoking, alcohol intake, hypertension, diabetes (i.e., type 1, type 2, gestational), thyroid disease, exercise, and BMI (HR, 0.73; 95% CI, 0.63-0.85; P <.001). On the other hand, female sex was positively associated with AFib when height (HR, 1.39; 95% CI, 1.14-1.72; P = .001), height and weight (HR 1.49, 95% CI, 1.21-1.82; P <.001), or BSA (HR, 1.25; 95% CI, 1.06-1.49; P = .009) were substituted for BMI in the multivariate model.

In stratified models, the study found that risk factor associations with incident AFib were similar for women and men.

“In this cohort study, findings suggest that after controlling for height and/or body size, women without CVD at baseline were at higher risk for AF [AFib] than men, suggesting that sex differences in body size account for much of the protective association between female sex and AF,” the authors concluded. “These data underscore the importance of AF prevention in women.

AFib is the most common type of abnormal heart rhythm and, without treatment, can lead to stroke or heart failure, which is more common in women than men.

The patients diagnosed with the condition can be treated with blood thinners and outpatient procedures such as cardioversion, ablation, or heart surgery; however, women are less likely to undergo invasive treatments for AFib such as ablation, the study noted.

“With incidence on the rise, it’s more imperative than ever to be offering preventive strategies and early diagnostic interventions to all patients,” Dr. Albert advised.

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