Corrected BMJ Study Now Shows No Recent Change in Teen Smoking in US, Canada

By Lisa Rappaport

July 29, 2020

(Reuters Health) - The BMJ has issued a correction for a 2019 study on the prevalence of teen vaping and smoking in Canada, the U.S., and the UK to reflect government data released after publication that impacted the weighted prevalence estimates.

The original study indicated that smoking among youth 16 to 19 years old might have increased in Canada from 2017 to 2018. At the time, smoking rates among 15- to 19-year-olds in Canada had not declined from 2015 to 2019 - in an apparent end to several decades of steady decline, the researchers note in their update, published with the correction on July 10, 2020.

Subsequently, Health Canada released data from the Canadian Student Tobacco, Alcohol and Drugs Survey (CSTADS), which found no increase in teen smoking from 2016 through 2019, the researchers report in their updated analysis with new weighted estimates for teen smoking based on the new CSTADS data as well as updated data from the U.S. National Youth Tobacco Survey (NYTS).

The original paper reported a statistically significant increase in past 30-day smoking prevalence in Canada, from 10.7% in 2017 to 15.5% in 2018. But after reweighing the data to include the new CSTADS data, the researchers found there was no significant change in smoking from 2017 to 2018, with a shift from 10.7% to 10.0% in Canada.

"We have used this data to 're-weight' our published BMJ estimates, as the government survey represents the gold standard," said David Hammond of the School of Public Health at the University of Waterloo in Canada, who led the study.

"This doesn't mean that we conducted an 'error' in our calculations; indeed, at the time of our paper, two other national surveys indicated no decrease in smoking in Canada," Hammond said by email. "Our update does, however, recognize that the governments' survey is the authority and its estimates are the most authoritative indicators of smoking in Canada."

For U.S. teens, the corrected paper also reported new figures for teen smoking prevalence updated to reflect new NYTS data, although there was no significant change in U.S. teen smoking prevalence in the original paper or the corrected manuscript. In the original, rates went from 11.0% in 2017 to 12.2% in 2018, and in the corrected manuscript, the change is from 11.0% to 11.7%.

Reuters Health reported on the original study last year, but didn't report on the smoking data, focusing instead on data related to youth vaping. The increase in teen vaping, which did not have any data revised in the corrected manuscript, suggests that the availability of e-cigarettes with more nicotine may partly explain the trend.

The original study examined data on smoking and vaping by youth in Canada, England and the U.S. and found that between 2017 and 2018, the proportion of 16- to 19-year-olds who reported vaping in the past 30 days rose by almost 50% in the U.S. and nearly doubled in Canada, while remaining relatively constant in the UK.

The proportion of teens who said they had vaped in the previous 30 days rose in Canada from 8.4% in July - August 2017 to 14.6 % in August - September 2018, and in the U.S. from 11.1% to 16.2% while remaining stable at just under 9% in the UK.

"2018 marked the point at which new vaping technology started to take over the market, led by JUUL," Hammond said at the time the original study was published.

"The vapor from these products has a different chemistry that allows them to deliver very high levels of nicotine, similar to regular smoked cigarettes," Hammond said. "However, England has set maximum limits on nicotine concentrate, which cuts the nicotine level in half compared to the same brands sold in Canada and the U.S., and England has also more strict rules on advertising of e-cigarettes than the other two countries."

JUUL debuted its e-cigarettes in the U.S. in 2015 and "now commands more than half the market," the researchers noted in their original 2019 report. JUUL became available in the UK in July 2018 and in Canada in September 2018.

Teen use of JUUL e-cigarettes increased in all three countries during the study period. The proportion of U.S. adolescents who reported JUUL was their usual brand surged threefold between 2017 and 2018, from 1% to 4.5%.

Many youth think vaping is not harmful and many are unaware of the nicotine levels in the current generation of products, Hammond said at the time the original study was published. He added, "Parents and kids should know that these products are capable of producing addiction and may have long term health risks from exposing the lungs to chemicals from e-cigarettes."

At the time the original study was published, JUUL said, "We don't want any non-nicotine user to use our products, especially youth," in an emailed statement. "We agree with the authors of the study about the need to find 'the optimal regulatory balance that provides smokers with reasonable access to these products, while restricting features of such products that appeal to youth . . .' and our actions to prevent underage use reflect that. We have taken aggressive action in both the U.S. and Canada to combat underage usage of our products while preserving the opportunity for adult smokers to switch from combustible cigarettes."

Children and teens need to be counseled about the dangers of smoking and vaping, Professor Linda Bauld, chair of public health at the College of Medicine and Veterinary Medicine at the University of Edinburgh, UK, who coauthored an editorial accompanying the original study, said at the time.

"Vaping products are for adult smokers trying to quit, not teenagers who have never smoked," Bauld said. "Vaping is less harmful than smoking, that's why it is a good option for adult smokers. But that doesn't mean that it is risk free and it is better for teenagers to use nothing - no vaping, no smoking."

SOURCE: The BMJ, online July 10, 2020; and The BMJ, online June 20, 2019.


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