Epidemiological studies are increasingly contradicting claims that e-cigarettes are less harmful than conventional combustible cigarettes.
◇ Adolescents Using Liquid and Heated Tobacco Face 13.72-Fold Higher Asthma Risk
Asthma is a condition in which chronic inflammation in the bronchial tubes makes the airways sensitive and narrow, causing repeated coughing and breathing difficulties. Adolescents in their growth period are particularly vulnerable to tobacco smoke because their lungs have not fully matured. Ultrafine particles and chemicals emitted from e-cigarettes and heated tobacco products can worsen airway inflammation and increase bronchial hypersensitivity, potentially contributing to the onset and aggravation of asthma symptoms.
According to a paper published in the latest issue of the international journal Tobacco Induced Diseases by a research team led by Lee Sung-kyu, director of the Korea Center for Tobacco Control Research and Education, an analysis of 159,383 middle and high school students nationwide who participated in the 2022-2024 Youth Health Behavior Survey found that 1.7% had been diagnosed with asthma within the past year.
The concern is that asthma risk varied significantly by smoking type. Compared with non-smokers, adolescents who smoked only conventional cigarettes had a 1.34-fold higher asthma risk. However, the risk surged to 4.34-fold for those using only liquid e-cigarettes and 9.16-fold for those using only heated tobacco products. Notably, adolescents who used both liquid e-cigarettes and heated tobacco faced an asthma risk as high as 13.72-fold.
The warning signs were more pronounced among users of new tobacco products than among conventional cigarette users. "Harmful substances contained in e-cigarette aerosols (vapor), including ultrafine particles, heavy metals, formaldehyde and acetaldehyde, can damage and inflame the airways of adolescents whose immune systems are still immature, triggering or worsening asthma," Lee said. Contrary to the tobacco industry's marketing of these products as less harmful, new tobacco products are directly threatening adolescents' lungs.
◇ Liquid E-Cigarettes Now Classified as Tobacco
According to the "2026 Youth Statistics" recently released by the Ministry of Gender Equality and Family, the smoking rate among middle and high school students stood at 3.3% last year, down 0.3 percentage point from the previous year. A notable trend is the emergence of "multiple nicotine consumption," in which adolescent smokers concurrently use conventional cigarettes, heated tobacco products and liquid e-cigarettes.
According to a Korea Disease Control and Prevention Agency survey, the proportion of adolescent smokers using both conventional and electronic cigarettes rose to 61.4% last year, up from 47.7% in 2019. Other surveys have shown that more than 70% of adolescents start using tobacco products with flavored tobacco, such as liquid e-cigarettes.
Until recently, liquid e-cigarettes were not subject to regulation under the Tobacco Business Act, lowering the barrier of access for adolescents. However, following a recent revision to the Tobacco Business Act, liquid e-cigarettes have begun to be classified as tobacco. With liquid e-cigarettes — long cited as a key factor driving up adolescent smoking rates — now falling under the regulatory framework, expectations are growing that the change will be more effective in deterring youth smoking.
◇ E-Cigarettes Double Abdominal Obesity Risk
Some claim that e-cigarettes help with weight management by suppressing appetite. In reality, however, e-cigarette users showed a higher risk of abdominal obesity.
According to the latest issue of the international journal Medicina, a joint research team from Catholic Kwandong University and Yonsei University Wonju College of Medicine analyzed 17,890 adults using data from the Korea National Health and Nutrition Examination Survey. The results showed that e-cigarette users had a 1.98-fold higher risk of obesity and a 2.03-fold higher risk of abdominal obesity than non-smokers.
The risk was even greater for "dual users" who smoked both conventional cigarettes and e-cigarettes. Compared with conventional cigarette smokers, dual users had a 1.42-fold higher risk of obesity and a 1.30-fold higher risk of abdominal obesity, the team estimated.
Experts point out that while nicotine may temporarily appear to suppress appetite, over the long term it stimulates the body's stress hormones cortisol and catecholamines, inducing insulin resistance. They also note that e-cigarette users and dual smokers tend to absorb more nicotine overall, or experience relatively higher stress levels and irregular eating habits, which may further fuel obesity risk.
In this study, the risk of obesity and abdominal obesity after smoking cessation was 1.4-fold higher than among non-smokers, but no statistical significance was observed after adjusting for major confounding variables, including sex, age, physical activity, alcohol consumption, hypertension and diabetes.
"Weight gain after smoking cessation does not necessarily lead to general obesity or abdominal obesity, suggesting that the relationship between quitting smoking and obesity may be influenced by various lifestyle and clinical factors," the research team said. "Additional research is needed to clarify the causal relationship between smoking cessation and weight gain."
