Smoking More Strongly Linked to Long-term Risks of PAD Than to Other Types of CVD

The well-known detrimental effects of smoking on cardiovascular health are greatest—and longest-lasting—when it comes to PAD, an analysis of the ARIC cohort shows.

Heavier smokers had elevated risks of coronary heart disease (CHD), stroke, and PAD over decades of follow-up, but the relationships were strongest for peripheral disease, lead author Ning Ding, MBBS (Johns Hopkins Bloomberg School of Public Health, Baltimore, MD), and colleagues report.

What’s more, even though quitting started to bring down those risks within 5 years, former smokers remained at risk for decades—up to 30 years for PAD and 20 years for CHD—compared with people who had never smoked.

Both of those findings—the strong association with PAD and the lingering effects of smoking even after kicking the habit—are important messages to convey to the public, especially younger people who might be considering whether to start smoking, senior author Kunihiro Matsushita, MD, PhD (Johns Hopkins Bloomberg School of Public Health), told TCTMD.

“Public health statements have been focusing on the impact of smoking on coronary heart disease and stroke, so I think our study suggests that future policy statements may want to consider the impact of smoking on peripheral artery disease so the message can be more comprehensive than the previous statements,” he said.

Smoking Harms, Any Way You Measure It

Matsushita noted that the link between smoking and CVD has been recognized for a long time, but no prior studies have assessed the impact of smoking on CHD, stroke, and PAD in a single study population.

Our study suggests that future policy statements may want to consider the impact of smoking on peripheral artery disease so the message can be more comprehensive. Kunihiro Matsushita

He and his colleagues did just that in this new study, published online ahead of the July 30, 2019, issue of the Journal of the American College of Cardiology. They further distinguished their effort by considering changes in smoking status over time as well as multiple measures of how much people smoked. Their cohort came from the Atherosclerosis Risk in Communities (ARIC) study and consisted of 13,355 people ages 45 to 64 who did not have atherosclerotic disease at baseline in 1987-1989; at that time, 25% were current smokers, 31% were former smokers, and 44% had never smoked.

Through a median follow-up of 26 years, dose-response relationships were seen between pack-years of smoking and risks of CHD, stroke, and PAD. The magnitude of the relationship was greatest for PAD, however. For example, compared with people who had never smoked, those who had at least 40 pack-years in their past were 3.68 times as likely to develop PAD, 2.14 times as likely to develop CHD, and 1.81 times as likely to have a stroke. Similar patterns emerged when looking at smoking duration or intensity (packs per day).

The strength of the link to PAD “seems quite striking,” Matsushita said, adding that more research is needed to nail down why it’s more tightly tied to smoking than CHD or stroke. “We suspect that it may be related to some kind of unique hemodynamics in the leg arteries, and also the atherosclerotic burden can be especially important in leg arteries,” he said.

Quitting smoking was associated with a lowering of the risks of all three atherosclerotic diseases, with the largest reductions seen for PAD. Still, risk among former versus never smokers persisted longer for PAD than for CHD or stroke.

Taking a Good Clinical History Is Key

Commenting for TCTMD, Jacob Udell, MD (University of Toronto, Canada), said it’s unclear why smoking would be particularly harmful in terms of PAD. “Perhaps it’s something to do with the small vessels. Perhaps it’s something to do with the lower extremities per se. We don’t really entirely understand why those vessels are more susceptible,” he said.

The study “just really underscores all the different ways that smoking characteristics can amplify not only coronary disease but [also] peripheral arterial disease in particular and how long the effects can last even after patients stop smoking,” he said.

Those findings highlight the importance of taking a good clinical history—including questions about smoking—in patients with PAD, according to Udell.

There are still demographic groups that are seeing a stubbornly pervasive use of smoking, and if we’re not asking the questions, I think clinically it’s pretty difficult then to target people for cessation and best yet would be prevention. Jacob Udell

“We sometimes stop at the amount of smoking and the amount of packs you smoke a day, but we don’t really get at when did you start smoking as well and the intensity in terms of how often they were smoking at the time because we can only be looking at the most recent proximal amount of smoking and not really consider their lifelong intensity,” he said.

Udell, who wrote an editorial for another study in the same issue of JACC that found that the relationship between low education level and subclinical atherosclerosis was largely mediated by increased smoking, offered some public health messages, too.

“Smoking still remains quite pervasive, particularly in the lower socioeconomic stratum. And now with smoking we’re starting to see an offset in terms of vaping, and we think vaping might be healthier but we really don’t know,” he said. Though overall rates of smoking are trending down, he added, “there are still demographic groups that are seeing a stubbornly pervasive use of smoking, and if we’re not asking the questions, I think clinically it’s pretty difficult then to target people for cessation and best yet would be prevention.”

In an editorial accompanying the ARIC analysis, Nancy Rigotti, MD (Massachusetts General Hospital, Boston, MA), and Mary McDermott, MD (Northwestern University Feinberg School of Medicine, Chicago, IL), say the findings “reinforce the existing public health message for smokers: it is never too early or too late to benefit from quitting. It is never too late because of the relatively rapid reversal of CVD risk after smoking cessation and never too early because complete risk reversal requires decades—even longer for PAD than for myocardial infarction or stroke, as this report demonstrates.”

The study also reminds clinicians about the importance of managing tobacco use in their patients, Rigotti and McDermott say, noting that the American College of Cardiology recently released an expert consensus decision pathway on tobacco cessation treatment to help guide that effort.