Cigarette smoking is linked to between 80 and 90 percent of lung cancer deaths in the United States, according to the CDC. Because ties between vaping and lung cancer are still developing — and it's often (perhaps incorrectly) assumed that vaping is healthier than smoking cigarettes — vapers may feel they're sidestepping some of that risk.
But the lungs are only part of the story: An estimated one in five smoking-related deaths are due to heart disease. And when it comes to heart disease, a growing pile of research suggests that a vaper's heart is still vulnerable.
A study published Tuesday in the Journal of the American Heart Association found that smoking and vaping are both harmful to heart health. The team found that smokers and vapers has similar measures of arterial stiffness. Jessica Fetterman, the study's first author and an assistant professor at Boston University, explains this kind of arterial stiffness is a precursor of heart disease.
"Stiffening of the arteries can cause damage to the small blood vessels, including capillaries, and puts additional stress on the heart, all of which can contribute to the development of heart disease," she says.
The heart never ends up drenched in flavored vapor, but nevertheless — it may bear the brunt of vaping's long-term cost.
Numerous studies suggest that vaping extracts a high toll on the heart. One March 2019 survey of 96,000 vapers found that vapers were 34 percent more likely to have a heart attack and 25 percent more likely to have coronary artery disease than non-vapers.
This study, though, drills a bit deeper than a survey.
The scientists investigated arterial stiffness in four groups: smokers (285 people), vapers (36 people), dual users (52 people), and people who neither smoked, nor vaped (94 people). The dual users had the stiffest arteries followed by the cigarette smokers, then the vapers, and finally the non-vapers.
Still, the authors report that the augmentation index – a measure of arterial stiffness – was "similar" between the vapers and the non-vapers. The difference between the two groups was not statistically significant. That suggests vaping and smoking both have harmful effects on arterial stiffness.
It's important to note that all the vapers in this study had previously been cigarette smokers, so it's hard to tease apart the effects of vaping alone from this study. Fetterman tells Inverse that she focused on vapers who used to be smokers because "the vast majority of adult e-cigarette users are former or current traditional cigarette smokers."
That said, it doesn't spell good news for those who turn to vaping to help quit smoking, hoping to sidestep a litany of long-term health effects.
Why does vaping appear to affect heart health? — This study points towards a few reasons that vaping could contribute to heart conditions later on, especially when combined with earlier work.
Past research suggests that vaping can change the way blood moves through the body, even when nicotine isn't in the picture. A 2019 Radiology paper found that after 31 adults had a heavy vaping session, blood flow to the femoral artery (a large artery in the thigh) slowed by 25.8 percent. They also found that dilation of that artery, which opens it up to blood flow, decreased by 34 percent.
Those changes were temporary and went back to normal after the session was over. But the concern is that, over time, those changes could cause lasting changes to blood vessels, as Inverse reported previously.
Since that study has come out, more research has suggested that vaping can alter blood pressure. Another new study, which was slated to be presented at the 2020 Experimental Biology conference before it was canceled due to the coronavirus, focused on 15 young, healthy non-smokers who JUULed while scientists monitored their blood pressure. As they vaped, they either received a non-nicotine e-liquid or a nicotine-laden e-liquid.
When they got doses of nicotine (which are extremely high in JUUL pods), blood pressure and heart rate spiked significantly, compared to the placebo. Blood pressure remained elevated, even after the vapers were allowed to step away from their JUULs to cool down for 10 minutes.
The authors concluded that even non-smokers who JUUL place themselves at higher risk for high blood pressure.
In context with those studies, Fetterman's study offers a deeper look at what is happening within the cells of a vaper (or smoker) that might contribute to these changes in blood vessels. This is because her team specifically analyzed cell samples.
In turn, the team found that cell samples from vapers and dual users produced lower levels of nitric oxide, a compound that allows blood vessels to remain flexible and dilate in response to blood flow — Fetterman calls it a "heart-protective" compound that can inhibit inflammation, prevent blood clots from forming and help blood vessels to redirect blood flow.
They also found that their cells were produced reactive oxygen species, rogue chemicals which can cause DNA damage or cell death.
Together, a lack of nitric oxide and an abundance of reactive oxygen species could be causing arterial stiffness, says Fetterman.
"It is likely that the loss in nitric oxide production and increased oxidative stress contributes to the arterial stiffness in tobacco users. Reactive oxygen species themselves can deplete the amount of nitric oxide available to maintain healthy blood vessels," she explains.
Still, like many of these studies, the limiting factor is time. We're still looking at vaping in terms of months or years, not necessarily decades. Then effects on the heart may become more clear, but for now, we're starting to get a hazy glimpse of that future. Meanwhile, evidence suggests that vaping might not be a safer alternative to cigarettes, at least when it comes to the heart.
Methods and Results: We examined the association of e-cigarette use with measures of vascular function and tonometry, preclinical measures of cardiovascular injury. As part of the Cardiovascular Injury due to Tobacco Use (CITU) study, we performed non-invasive vascular function testing in individuals without known cardiovascular disease (CVD) or CVD risk factors who were non-smokers (N=94), users of combustible cigarettes (N=285), e-cigarettes (N=36), or dual users (N=52). In unadjusted analyses, measures of arterial stiffness including carotid- femoral pulse-wave velocity (PWV), augmentation index, carotid-radial PWV and central blood pressures differed across the use groups. In multivariable models adjusted for age, sex, race, and study site, combustible cigarette smokers had higher augmentation index compared to non- users (129.8 ± 1.5 vs 118.8 ± 2.7, P=0.003). The augmentation index was similar between combustible cigarette smokers compared to sole e-cigarette (129.8 ± 1.5 vs 126.2 ± 5.9, P=1.0) and dual users (129.8 ± 1.5 vs 134.9 ± 4.0, P=1.0). Endothelial cells from combustible cigarette smokers and sole e-cigarette users produced less nitric oxide in response to A23187 stimulation compared to non-smokers, suggestive of impaired eNOS signaling.
Conclusions: Our findings suggest that e-cigarette use is not associated with a more favorable vascular profile. Future longitudinal studies are needed to evaluate the long-term risks of sustained e-cigarette use.