E-cigarettes Tied to Lower Sperm Counts in Young Men

By Marilynn Larkin

July 07, 2020

NEW YORK (Reuters Health) - Use of e-cigarettes, like regular cigarette smoking, was associated with lower sperm counts among young men in an observational study.

Drs. Laerke Priskorn and Stine Agergaard Homboe of the University of Copenhagen told Reuters Health by email that that the research team has been monitoring semen quality and factors associated with it since 1996. Young men in the general population provide semen and a blood sample and fill out a lifestyle questionnaire as part of a compulsory physical at age 18 to determine fitness for military service.

"We noticed that more men in recent years mentioned electronic cigarettes and snuff in relation to their smoking habits, which traditionally focused on cigarettes," they said. "Therefore, we started to ask the men specifically about their use of such products, as the association of e-cigarettes and testicular function had not been studied in humans."

As reported in Human Reproduction, Drs. Priskorn, Homboe and colleagues analyzed data from 2,008 men (median age, 19), who provided information on cigarette and marijuana use between 2012 and 2018, including 1,221 (61%) enrolled between 2015-2018 who also gave information on e-cigarettes and snuff.

Approximately half of the men (52%) were cigarette smokers, 13% used e-cigarettes, 25% used snuff and 33% used marijuana. E-cigarettes and marijuana users were often also cigarette smokers.

After adjustment, compared to non-users, daily e-cigarette users had significantly lower total sperm count (91 million versus 147 million), as did daily cigarette smokers (103 million versus 139 million).

Notably, however, only 25 men (2%) reported using e-cigarettes daily, and 139 (11.4%) reported occasional use. The majority of daily e-cigarette users said the e-liquid contained nicotine, and thus the impact of daily e-cigarette use without nicotine content could not be examined. Nonetheless, for the occasional users, associations were similar as for daily users, irrespective of nicotine content.

Furthermore, compared to non-smokers, significantly higher total and free testosterone levels were seen in cigarette-smoking men: 6.2% higher total testosterone in daily smokers and 4.1% higher in occasional users - and 6.2% higher free testosterone in both daily and occasional smokers. These differences were not seen among e-cigarette users.

Daily users of marijuana had 8.3% higher total testosterone levels compared to non-users, whereas no associations were observed for snuff in relation to markers of testicular function.

Despite limitations of small numbers and possible behavioral factors not adjusted for, "this is the first human study to indicate that not only cigarette smoking but also use of e-cigarettes is associated with lower sperm counts," the authors state. "This could be important knowledge for men trying to achieve a pregnancy, as e-cigarettes are often considered to be less harmful than conventional cigarette smoking."

Drs. Priskorn and Homboe affirmed, "Based on this study, use of e-cigarettes cannot be considered a better alternative to cigarette smoking regarding effects on testicular function."

"However," they added, "the number of e-cigarette users in our study was limited, and the results need confirmation in larger studies. Furthermore, studies examining e-cigarettes with and without nicotine content and with different types of flavoring, including assessment of the users' chemical profile, are needed to better understand the observed association."

Dr. Michael Thomas, Professor and Chair, Department of Obstetrics and Gynecology at the University of Cincinnati College of Medicine in Ohio, noted in an email to Reuters Health, "lower sperm counts don't mean no pregnancy. Lower counts in the normal range will still allow pregnancy, and therefore, cigarettes and e-cigarettes are not a form of contraception."

"Also, the data on e-cigarettes are interesting because they allude to the fact that cigarettes and e- cigarettes cause the same adverse effect," he said. "I think (the cause) is decreased oxygenation. But a larger study is necessary to see any true differences."

SOURCE: https://bit.ly/3gg9DGi Human Reproduction, online June 19, 2020.