Atrial fibrillation, a condition characterized by an irregular heart rate, is the most common type of heart arrhythmia, affecting between 2.7 and 6.1 million people in the United States. People with this ailment may experience lightheadedness, extreme fatigue, chest pain, shortness of breath and heart palpitations. However, the number of these symptoms patients experience, and how the condition affects their general wellbeing, may vary depending on their sex, according to new research published in JAMA Cardiology .

“While there are well documented sex-based differences in treatment, health status, and other clinical outcomes in other cardiovascular diseases, these have been infrequently described in [atrial fibrillation],” researchers wrote.

The researchers from Duke University Medical Center combed through data regarding more than 10,000 patients who were part of the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation — a nationwide, multicenter outpatient registry of patients with the condition. The registry included information on patients’ quality of life, symptoms, daily activities, treatment concerns, and treatment satisfaction. Forty-two percent of the cohort were women, and their average age was a bit older than men’s (77 vs. 73 years old).

The data showed that women experienced more symptoms and functional impairment and had a worse quality of life, despite having less persistent forms of atrial fibrillation. Researchers found they also had a 40 percent higher risk of stroke, and were more likely to undergo atrioventricular node ablation, a surgical procedure that’s performed when medications do not work to control rapid heart rates. However, despite having a worse quality of life and a higher risk of experiencing adverse health events, women had a higher risk of survival and a lower risk of cardiovascular death than men.

Because the reasons for these sex differences are unclear, the researchers said there’s a need for further research that focuses on how treatment and interventions specifically affect cardiovascular outcomes in women and men with atrial fibrillation.

“The differences in therapies and response may shed light on important factors associated with disease progression and modification of risk,” researchers wrote. “For example, it is possible that rate and rhythm-control therapies affect disease progression and subsequent quality of life differently in men and women.” If that’s the case, then these differences will be considered in studies that also incorporate other characteristics that are more unique to the individual.

Previous studies had linked atrial fibrillation to depression. However, one limitation of the current study was that it failed to determine whether the sex differences in symptoms and quality of life were influenced by depression or caused by it — an important factor, considering women are nearly twice as likely to develop depression than men. Another limitation: the researchers failed to assess the extent to which the palpitations and other symptoms were actually caused by atrial fibrillation. You see, these symptoms aren’t always caused by atrial fibrillation, “thus, the extent to which these symptoms reflect true arrhythmia in women vs. men is also unknown.”

Source: Piccini J, Simon D, Steinberg B, et al. Differences in Clinical and Functional Outcomes of Atrial Fibrillation in Women and Men. JAMA Cardiology. 2016.