Asthma, especially if poorly controlled, may increase the risk of atrial fibrillation (AF), JAMA Cardiology reports.

In a study which included 54,567 adults, 10.9 per cent reported ever having asthma, 7.2 per cent had been diagnosed with asthma and 4.6 per cent had active asthma. During a mean follow-up of 15.4 years, 3.8 per cent developed AF. Moreover, 5.4 per cent reported controlled asthma, 3.3 per cent partly controlled asthma and 1.0 per cent uncontrolled asthma.

Allowing for potential confounders, people who reported ever having asthma were 27 per cent more likely to develop AF than controls without asthma. Those people with diagnosed asthma were 38 per cent more likely to develop AF, while active asthma increased the risk by 76 per cent.

The 16 per cent increased risk of AF was not significantly different in people with controlled asthma compared to controls, but people with partly controlled and uncontrolled asthma were 40 and 74 per cent more likely to develop AF.

Several factors could link the conditions. For instance, high levels of systemic inflammation are common in uncontrolled asthma and AF, while beta-2 adrenergic agonists influence heart rate and increase the risk of arrhythmias. Statistical analysis, however, suggested that cardiovascular risk factors or co-morbidities did not account for the relationship.

The authors also “found no clear evidence” that either beta- 2 agonists or high-sensitivity C-reactive protein (hsCRP) levels, a marker of inflammation, mediated the association.

Further studies – including more detailed investigations of medication use and inflammation – need to clarify the mechanisms. In the meantime, the authors say that “given the high prevalence of asthma, clinicians should be aware of this connection and closely examine AF risk factors in this patient group”.

(doi:10.1001/ jamacardio.2018.1901)