Secondhand Smoke Tied to Higher Risk of Incident AF

BERLIN, Germany—People who are exposed to secondhand tobacco smoke appear to have a greater risk of developing atrial fibrillation (AF), according to an analysis of data from the UK Biobank.

Those with any level of exposure had an incident AF risk that was a relative 6% higher through long-term follow-up compared with those who were unexposed (adjusted HR 1.06; 95% CI 1.03-1.10), Kyung-Yeon Lee, MD (Seoul National University Hospital, Republic of Korea), reported here at the European Heart Rhythm Association Congress 2024.

That relationship was even stronger among individuals who had a genetic predisposition to AF.

“Minimizing secondhand smoke exposure, especially in individuals with a heightened genetic susceptibility to AF, may hold potential benefits for reducing the future risk of AF,” Lee concluded.

Although prior studies have shown an association between secondhand tobacco smoke and a greater susceptibility to arrhythmias, including AF, the epidemiologic link between secondhand smoke exposure and incident AF remains controversial, Lee said.

To further explore the question, she and her colleagues turned to the UK Biobank. After exclusion of individuals with a prior diagnosis of AF and current smokers, the analysis included 400,493 people (mean age 56.5 years; 55.2% women). Roughly one-fifth of participants reported exposure to secondhand smoke on a questionnaire (mean 2.2 hours per week).

During a median follow-up of 12.5 years, 5.9% of individuals received a new diagnosis of AF, with the risk being higher among those who had reported secondhand smoke exposure after adjustment for various potential confounders. The relationship was consistent irrespective of whether the exposure occurred in the home (adjusted HR 1.10; 95% CI 1.03-1.17) or outdoors (adjusted HR 1.06; 95% CI 1.02-1.09).

The relationship was dose-dependent, with the risk rising along with hours of exposure. Those who reported being around secondhand smoke for an average of 7.7 hours per week, for instance, had an 11% greater risk of developing the arrhythmia compared with their unexposed peers (adjusted HR 1.11; 95% CI 1.03-1.20).

Moreover, individuals with the greatest genetic susceptibility to AF based on a polygenic risk score had an even higher risk of incident AF related to secondhand smoke exposure.

Commenting for TCTMD, Juhani Junttila, MD, PhD (Medical Research Center Oulu, Finland), co-chair of the moderated poster session at which Lee presented the results, called the findings interesting but noted that there are many potential confounders in large, population-based analyses like this one.

In this case, he suspects secondhand smoke exposure is serving as a marker of lower socioeconomic status, which itself has been associated with environmental and acquired factors tied to AF in the general population.

Still, Junttila said, “smoking is bad for you, of course, and secondhand smoking needs to be taken into account also when you’re thinking about this factor. But also for all cardiovascular risk factors, secondhand smoking is important, so that’s something that we need to keep in mind.”

Junttila also indicated that this analysis highlights the continuing importance of population-based studies like the UK Biobank, saying, “It’s really nice to see that these really large registries are used.”