First epidemiological evidence linking e-cigs to cancer in people

E-cigarette advocates like to point out that because there is no combustion, e-cigarettes expose users to lower levels of many carcinogens (cancer-causing chemicals).  Even so, there are still some carcinogens in e-cigarette aerosol exposure to e-cigarette aerosol damages DNA and reduces repair in animal and human cells and causes cancer in animals.  Now there is also direct evidence that people who use e-cigarettes are at increased risk of some cancers.

In February 2022, Anusha Chidharla and colleagues at several universities published “Cancer Prevalence in E-Cigarette Users: A Retrospective Cross-Sectional NHANES Study” in World Journal of Oncology.  Using data from the large US National Health and Nutrition Examination Survey they found that, while e-cigarette users had lower overall cancer risk than smokers, e-cigarette use was associated with higher risks of some cancers than smoking cigarettes, including cervical cancer, leukemia, skin cancer (non-melanoma), skin (other) and thyroid cancers (P < 0.0001).

The interesting thing about this finding is that these are not the major smoking-induced cancers (lung and bladder).  This result reinforces the view than e-cigarettes are not simply cigarettes without some of the bad chemicals; they expose users to a different mix of toxic chemicals than cigarettes.

E-cigarette users were also diagnosed with cancer at younger ages than smokers.

While this is the first epidemiological study that links e-cigarettes to cancer, it highlights the need for more work in this area, especially looking beyond the most common smoking-caused cancers.  It also means that e-cigarette advocates and regulators like the FDA need to stop being so glib about e-cigarettes and cancer.

Here is the abstract:

Background: It is well known that traditional smoking causes various types of cancer, leading to the current decline in traditional smoking among US adults from 20.9% in 2005 to 14.0% in 2019. Electronic cigarettes (e-cigarettes) are commonly marketed as a safe alternative and gaining popularity especially among never-smokers and adolescents. However, there is limited evidence of effects of e-cigarette on cancer. Hence, we aim to find the prevalence and association of e-cigarette and traditional smoking among cancer respondents.

Methods: We conducted a retrospective cross-sectional study using the NHANES database from 2015 to 2018. We assessed history of cancer (MCQ220), type of cancers (MCQ230a), and smoking status (e-cigarette: SMQ900 or SMQ905 and traditional smoking: SMQ020) using questionnaires. We performed multivariable logistic regression models to find the association of e-cigarette use, traditional smoking, and no smoking with cancer after adjusting for confounding variables.

Results: A total of 154,856 participants were included, of whom 5% were e-cigarette users, 31.4% were traditional smokers, and 63.6% were nonsmokers. There is a higher prevalence of e-cigarette use among younger participants, females (49 vs. 38) in comparison to traditional smokers (P < 0.0001). The e-cigarette users have lower prevalence of cancer compared to traditional smoking (2.3% vs. 16.8%; P < 0.0001), but they were diagnosed with cancer at a younger age. Among cancer subtypes, cervical cancer (22 vs. 2.6), leukemia (8.5 vs. 1.1), skin cancer (non-melanoma) (15.6 vs. 12.3), skin (other) (28 vs. 10) and thyroid (10.6 vs. 2.4) had higher prevalence of e-cigarette use compared to traditional smokers (P < 0.0001). Our regression analysis showed that e-cigarette users have 2.2 times higher risk of having cancer compared to non-smokers (odds ratio (OR): 2.2; 95% confidence interval (CI): 2.2 – 2.3; P < 0.0001). Similarly, traditional smokers have 1.96 higher odds of having cancer compared to nonsmokers (OR: 1.96; 95% CI: 1.96 – 1.97; P < 0.0001).

Conclusion: In our study, e-cigarette users had an early age of cancer onset and higher risk of cancer. Hence, this is stepping stone for future research to evaluate the safety and effects of e-cigarettes in patients with cancer.

The full citation is: Chidharla A, Agarwal K, Abdelwahed S, Bhandari R, Singh A, Rabbani R, Patel K, Singh P, Mehta D, Manaktala PS, Pillai S, Gupta S, Koritala T. Cancer Prevalence in E-Cigarette Users: A Retrospective Cross-Sectional NHANES Study. World J Oncol. 2022 Feb;13(1):20-26. doi: 10.14740/wjon1438. Epub 2022 Feb 8. PMID: 35317331; PMCID: PMC8913014.  It is available here.