New research has identified some of the differences between men and women when it comes to their risk of developing A-fib.
The results of the Biomarker for Cardiovascular Risk Assessment in Europe (BiomarCaRE) Consortium study have been published in the journal Circulation.
Atrial fibrillation (A-fib) is a type of irregular heartbeat, or arrhythmia. It is a condition in which the atria — or the upper chambers of the heart — quiver or flutter as they pump blood into the lower chambers, or the ventricles.
Untreated A-fib is linked to a five times higher risk of stroke, and it is also known to raise the risk of dying from a heart-related condition. In the new study, the researchers found that it tripled the risk of death.
A-fib is thought to affect up to 6.1 million people in the United States. This number is expected to rise as the population ages: it affects around 9 percent of people aged 65 and over and around 2 percent of people under that age.
Need for better prevention
"It's crucial to better understand modifiable risk factors of atrial fibrillation," explains lead author Dr. Christina Magnussen, a specialist in medicine at the University Heart Center in Hamburg, Germany. "If prevention strategies succeed in targeting these risk factors, we expect a noticeable decline in new-onset atrial fibrillation."
Fewer people would get sick and die prematurely, and there would be significant cost savings, she adds. Every year in the U.S., around 750,000 people are admitted to hospital because of A-fib, while 130,000 die of a condition related to it. The annual costs amount to around $6 billion.
For their study, the team analyzed records of 79,793 people aged between 24 and 97 participating in four European community studies in the BiomarCaRE consortium. The participants, 51.7 percent of whom were women, did not have A-fib when they enrolled.
Although some participants were followed for as long as 28.2 years, the median follow-up period was 12.6 years. During this time, 4.4 percent of the female participants and 6.4 percent of the male participants were diagnosed with A-fib.
Sex differences in A-fib risk
When they analyzed the results, the team found that by the age of 90, around 24 percent of the participants had developed A-fib.
However, there were some marked differences between men and women. For instance, rates of A-fib diagnosis rose steeply from age 50 in men and age 60 in women.
Also, the risk of developing A-fib was higher in men who had higher blood levels of the inflammation marker C-reactive protein.
In addition, while an increase in body mass index (BMI) was tied to raised risk of A-fib in both men and women, in men it raised the risk by 31 percent compared with 18 percent in women.
Dr. Magnussen and colleagues note that "[a]mong the classic risk factors, body mass index explained the largest proportion of AF [A-fib] risk."
They were surprised to find that — especially for women — having a higher total cholesterol level appeared to lower their risk of A-fib. Higher total cholesterol is a known risk factor for heart disease, and the researchers say that it is not clear why the study showed this result.
'Weight control is essential'
The study was not designed to explore the reasons why A-fib appears to develop differently in men and women. The team does highlight that a possible weakness of their study is that some participants may have had A-fib when they enrolled but it was not diagnosed.
They also note that it is possible that there may have been some "misclassification" of cases during the follow-up period. This "may have led to a lower incidence and a weakening of the associations of classical risk factors with incident AF and mortality."
However, a notable strength of the study is that it investigated A-fib in the general population and tracked individuals over a long period.
The participants were from northern and southern Europe, so the researchers suggest that while their findings can be generalized to other Caucasian populations, they may not apply to other groups.
The exception appears to be the link between higher BMI and risk for A-fib: this was so strong that the team suggests that it is likely to apply to all groups.
"We advise weight reduction for both men and women. As elevated [BMI] seems to be more detrimental for men, weight control seems to be essential, particularly in overweight and obese men."
Dr. Christina Magnussen