People who use e-cigarettes have a high rate of visual impairment, researchers say, and that association is independent of and in addition to traditional cigarette use.
The statistical correlation doesn’t prove that vaping causes visual impairment. But it parallels earlier studies that link tobacco smoking to visual impairment, and vaping to lung damage. And it raises new questions about whether e-cigarettes are a safe alternative.
Tobacco smoking studies have shown associations with cataracts, neovascular age-related macular degeneration, thyroid eye disease and primary open-angle glaucoma, as well as their better-known harms.
Billed as a safer alternative, e-cigarettes have gained popularity since 2003, when they were released in their current form, with a heating element and atomizer, said the study’s first author, Abhinav Golla, MD, from the University of California, Los Angeles.
“Though e-cigarettes do not contain tobacco, they do share two really important similarities with traditional cigarettes,” said Golla at the virtual Association for Research in Vision and Ophthalmology 2021 annual meeting. “They both have nicotine and they are both shown to create oxidative stress and decrease antioxidants.”
In addition to nicotine, e-cigarettes contain flavorings and solvents such as propylene glycol or glycerin. Nicotine may increase the risk of glaucoma by constricting blood vessels supplying the optic nerve, Golla said. Propylene glycol and vegetable glycerin have killed human cells in laboratory studies.
To look for an association between e-cigarettes and visual impairment, Golla and his colleagues analyzed data from 1.1 million respondents to the Behavioral Risk Factor Surveillance System, a nationwide annual telephone survey administered throughout the United States from 2016-2018.
They tallied responses to three questions:
“Are you blind or do you have serious difficulty seeing, even when wearing glasses?”
“Have you ever used an e-cigarette or other electronic vaping product, even just one time, in your entire life?”
“Do you now use e-cigarettes or other electronic vaping products every day, some days, or not at all?”
They found that 4.6% of the respondents were current e-cigarette users. Of these, 6.2% reported visual impairment. Another 16.8% were former e-cigarette users, of whom 5.8% reported visual impairments. Of the 78.6% who reported never using e-cigarettes, 4.7% reported visual impairment.
Golla and his colleagues adjusted for multiple factors that could confound the association they were examining: tobacco cigarette use, age, sex, race/ethnicity, marital status, education, employment status, family income, heavy alcohol use, body mass index, physical activity, and mental health.
They then calculated that the risk of visual impairment was increased by 14% for people who had ever vaped (odds ratio [OR] 1.14; 95% CI, 1.06 – 1.22, P = .0002) and 34% for people who currently vaped (OR, 1.34; 95% CI, 1.21 – 1.48, P < .0001), compared with people who had never vaped.
The researchers noted that people who had vaped were five times more likely to have smoked tobacco than those who hadn’t vaped (OR, 5.24; 95% CI, 5.12 – 5.36). Given that strong association, they looked at the subgroups: 41,897 people who vaped but never smoked tobacco, and 620,136 people who had never smoked either.
Once again adjusting for other risk factors, the researchers now found that the risk of visual impairment for current e-cigarette users was almost double the risk for those who had never used e-cigarettes (OR, 1.96; 95% CI, 1.48 – 2.60, P < .0001). But the risk for former e-cigarette users was no longer statistically significant (OR, 1.02; 95% CI, 0.89 – 1.18; P = .7604).
“Importantly, this association between e-cigarette smoking and visual impairment was independent of and in addition to traditional cigarette use,” Golla said. The association with visual impairment was even higher for vaping than for tobacco smoking, he added.
An observational study such as this one can’t show cause and effect, Golla acknowledged. There might be confounding variables for which the researchers did not adjust. Or the sample of survey respondents might be somehow biased.
A randomized controlled trial would not be ethical. But a longitudinal study would at least show which came first — the visual impairment or the e-cigarette use, he said.
“It is important to note that this study used self-reported data to investigate the association between e-cigarette smoking and visual impairment,” said Kam Chun Ho, PhD, a research fellow at the Singapore Eye Research Institute, in an email to Medscape Medical News. Asking people if they had ever used even one e-cigarette in their entire lifetime might have resulted in a sample of people whose vaping was insignificant. Also, any future study should adjust for patients’ eye diseases. And it should include objective measures of visual impairment. Ho was not involved in Dr Golla’s study.
Studies analyzing the mechanism by which vaping could cause visual impairment would also be useful, said Andrew Iwach, MD, clinical spokesperson for the American Academy of Ophthalmology and associate professor at the University of California, San Francisco.
It’s too early for ophthalmologists to tell their patients definitively that vaping will harm their vision, Iwach told Medscape Medical News. But ophthalmologists should note e-cigarette use along with other risk factors such as tobacco smoking, diabetes, high blood pressure, and cholesterol.
If patients ask about the relative risks of vaping and smoking tobacco, it’s an opportunity to discuss their overall health and encourage them to broach the subject with their primary care providers. “Maybe some might think that there’s no risk at all with e-cigarettes, and that might not be the case,” said Iwach, who was not associated with the study.
He emphasized that everyone should get a baseline eye examination.
Golla, Ho, and Iwach have disclosed no relevant relationships.
Association for Research in Vision and Ophthalmology (ARVO) 2021 annual meeting: Abstract. Presented May 1, 2021.
Laird Harrison writes about science, health and culture. His work has appeared in national magazines, in newspapers, on public radio and on websites. He is at work on a novel about alternate realities in physics. Harrison teaches writing at the Writers Grotto. Visit him at www. lairdharrison.com or follow him on Twitter: @LairdH
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