People exposed to secondhand smoke—sometimes called passive smokers—have a 51% higher risk of developing oral cancer compared with people who are not exposed, according to findings published in Tobacco Control.

In 2021, some 54,000 people are expected to be diagnosed with oral cancer, accounting for a little under 3% of new cancer cases in the United States, according to the National Cancer Institute.

While firsthand inhalation of tobacco smoke is known to cause oral cancer, it has not been clear whether secondhand smoke also leads to oral cancer, as it does for lung cancer.

Luís Monteiro, PhD, of the Instituto Universitário de Ciências da Saúde in Portugal, and colleagues set out to establish a possible link between exposure to secondhand smoke and the risk of developing oral cancer.

They carried out a systematic review and meta-analysis study using data available through May 10, 2020, from the PubMed, Web of Science, Scopus, Cochrane Library, Open Grey and ProQuest databases.

On the basis of eligibility criteria, the team shortlisted five studies. The total data set included 1,179 people who developed oral cancer and 5,798 control subjects who did not. Of these 3,452 people were exposed and 3,525 people were not exposed to secondhand smoke.

The researchers found that people who were exposed to secondhand smoke had a 51% higher risk of developing oral cancer. Moreover, the risk more than doubled if the duration of exposure was more than 10 or 15 years in comparison with people who were not exposed.

“This systematic review and meta-analysis supports a causal association between secondhand smoke exposure and oral cancer,” wrote researchers. “Our results could provide guidance to public health professionals, researchers, and policymakers to further support effective secondhand smoke exposure prevention programs worldwide.”

Click here to read the study abstract in Tobacco Control.

Click here to learn more about oral cancer.