Parental Smoking Predicts Atrial Fibrillation Risk in Adult Offspring

Patrice Wendling

September 24, 2019

Secondhand exposure to tobacco smoke enhances the risk for atrial fibrillation (AFib) later in life, a Framingham Heart Study analysis affirms.

After examining data from 2816 Framingham offspring participants, the results show an 18% increase in adjusted AF risk for each pack per day increase in parental smoking.

Given the power of mimicry among children, unsurprisingly, offspring of parents who smoked were more likely to report a history of smoking than those parented by nonsmokers (48% vs 37%; <.001).

This added risk factor, however, explained only 17% of the relation between parental smoking and offspring incident AF, although the 95% confidence intervals were wide (1.5 - 103.3), the authors reported today in the Journal of the American College of Cardiology.

AF is recognized as one of the most common causes of stroke and may be an important cause of dementia, kidney disease, myocardial infarction, and sudden death, senior author Gregory Marcus, MD, MAS, University of California, San Francisco, told theheart.org | Medscape Cardiology.

"We do have improving tools to treat the disease, but there has not been a sufficient focus on prevention of atrial fibrillation precisely because we didn't understand why people were getting atrial fibrillation much of the time," he said. "So one of the implications of this is that smoking is modifiable and something we can start with as early as possible, and, especially as parents, modeling healthy behavior almost certainly can have good consequences for offspring."

The findings may also open up new ways of thinking about the pathophysiology of AF and how exposures or differences during development might have "meaningful effects on heart disease that doesn't manifest for several decades," observed Marcus.

Amid a Global Crisis

The results resonate at a time when concerns are rising globally over the use of electronic cigarettes and vaping products. Last week, the US Food and Drug Administration (FDA) launched a criminal investigation into the growing number of cases of severe lung injury and death linked to e-cigarette use, while India banned the sale of e-cigarettes entirely.

"Passive smoking or passive vaping, however you cut it, is still dangerous and I think people have to be cognizant about protecting their children," Dhanunjaya Lakkireddy, MD, executive medical director of the Kansas City Heart Rhythm Institute in Overland Park, Kansas, and chair of the American College of Cardiology Electrophysiology Council, told theheart.org | Medscape Cardiology.

Although smoking rates have declined, he argues that legislation is needed to eliminate smoking all together from the public sphere because of the association between passive smoking and higher risks for coronary artery disease and, now, AF.

"The legislation around smoking has to really become very important because of the long-term implications this has on the future health of the world and the financial and social implications of the premature onset of these diseases, which were once considered to be diseases of an aging population but are no longer," Lakkireddy said. "They have become diseases of younger and middle-aged people."

Marcus shared those sentiments: "The message is that smoking avoidance and absolute cessation is ultimately the best solution, and e-cigarettes and vaping should not be considered suitable alternatives."

Although there is a sense that everyone knows smoking is harmful, he noted that about 15% of all Americans still smoke and that a big proportion of these are of childbearing age and younger individuals.

"So we still have a long way to go to really convince everyone that both direct and secondhand smoke exposure are harmful and worth avoiding," he said. "I think this demonstrates the kinds of unanticipated downstream harms that smoking has. Even when regulators are considering the overall costs of smoking, these sorts of effects have not been taken into account previously."

Framingham Cohorts

Although cigarette smoking has been linked to incident AF in several epidemiologic studies, little has been published on secondhand smoking and AF, the authors note. The team previously reported that exposure to cigarette smoking in utero or as a child increased the odds of AF in adulthood by as much as 40% in the Health eHeart Study; however, cigarette smoking and AF were self-reported.

The present study took advantage of the Framingham Heart Study, in which participants and their offspring were evaluated every 2 to 8 years and underwent routine surveillance for cardiovascular outcomes. Participants were considered to have AF if an ECG ever demonstrated AF or atrial flutter. Cigarette-smoking status was determined using serial standardized questionnaires.

Of the 5124 offspring cohort participants, parental smoking status was available for 2816, or 55%, which is a key limitation of the study, according to both men. Also, the study was unable to hone in on smoking behaviors during pregnancy or variations in exposure among children of divorced or single parents or with others living in the household.

Although it's possible these limitations led to a spurious false positive, Marcus said, it's more likely that it "primarily limited our power to detect a difference; so it's possible that the magnitude of the difference is actually greater than what we were able to report."

Overall, 82% of the 2816 offspring participants were exposed to secondhand smoke during up to the age of 18 years. The median number of parental cigarettes smoked was 10 per day. Overall, 14.3% of offspring developed AF over a median follow-up of just 40.5 years.

The study was not designed to determine why the age of AF onset was so young, but the offspring of nonsmokers may have been smokers or there may be a relationship between AF that is independent of conventional risk factors, like hypertension, diabetes, and advancing age, Marcus said.

"That also would fit with the theory, which has yet to be proven, that smoke exposure in the lungs, the pulmonary veins, and left atrium may do something to the structure or function of those organs," he said.

Marcus said the results have spurred another study, in which AF and other cardiovascular outcomes will be evaluated as part of the Health eHeart Study among the offspring of participants in the Childhood Health and Development Study, which examined smoking specifically during pregnancy among 15,000 women in the 1950s and early 1960s.

In an editorial accompanying the present study, Alanna Chamberlain, PhD, MPH, Mayo Clinic, Rochester, Minnesota, says that "these findings are a reminder to clinicians to document every patient's tobacco use and secondhand smoke exposure at every visit, and to offer smoking-cessation treatment to every smoker, as recommended by the 2018 American College of Cardiology Expert Consensus Decision Pathway on Tobacco Cessation Treatment."

The study was supported by the American Heart Association and National Institutes of Health. The Framingham Heart Study was supported by the National Heart, Lung, and Blood Institute. Marcus reports research funding from Jawbone Health, Eight, and Medtronic; and serving as a consultant for and holding equity in InCarda. Chamberlain reports having no relevant conflicts of interest.

J Am Coll Cardiol. 2019;74:1658-1664, 1665-1666. Abstract, Editorial

Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org | Medscape Cardiology, join us on Twitter and Facebook.

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