IMM thesis: E-cigarettes impact on lung health

The focus of this thesis is the impact of electronic (e)- cigarettes on lung health. Over the last decades, e-cigarettes have gained popularity, particularly among young individuals, as an alternative and safer option to traditional cigarettes. However, e-cigarettes can introduce various potentially harmful substances, including nicotine, to the user's lungs. This thesis aimed to improve our understanding of the short-term and long-term effects of e-cigarette use on the lungs with a translational approach.

• Can you tell us about some interesting results?

We investigated the effects of e-cigarettes on lung health using cross-sectional data from a Swedish population-based birth cohort known as BAMSE. Our findings revealed that individuals who used e-cigarettes were more likely to report respiratory symptoms such as productive cough compared to non-users. Moreover, those who used both e-cigarettes and traditional cigarettes had a higher risk of experiencing respiratory symptoms associated with chronic bronchitis or asthma compared to those who did not use any tobacco products. It is important to note that these observations were made among young people aged 22 – 25, who may not have been long-term e-cigarette users. This raises significant public health concerns, especially among the younger population.

We also conducted a clinical study where the long-term local and systemic effects of e-cigarettes on different parameters related to lung health were examined in e-cigarette users and compared with cigarette smokers, dual users of e-cigarettes and traditional cigarettes, and healthy non-smokers of any tobacco. Different biomarkers associated with airway inflammation and lung diseases were also examined using blood, sputum, and saliva samples. Our findings revealed that e-cigarette users exhibited increased airway sensitivity, similar to that observed in individuals with asthma. In addition, the investigated biomarkers were found to be elevated in e-cigarette users and dual users compared to healthy non-smokers, both locally and systemically. These findings were observed in individuals who had used e-cigarettes for less than 3 years, highlighting the harmful impact of e-cigarettes on lung health.

Lastly, this thesis investigated the effects of e-cigarettes on a cellular level using two lung models developed with human lung cells, representative of the bronchial and alveolar regions. After exposing these models to e-cigarette vapours from two fruit-flavoured e-liquids, we found that the effects of repeated and short-term exposures were influenced by the lung regions, the composition of the e-liquids/vapours, and the presence or absence of nicotine.

• What further research is needed in the area?

Further research is required to overcome the limitations of these studies. Conducting studies with larger sample sizes would provide a more comprehensive understanding of how factors such as the type of e-cigarette device, chemical compositions of e-liquids, nicotine content, and vaping behavior patterns can impact lung health. Additionally, long-term follow-up studies are required to determine whether prolonged use of e-cigarettes is associated with impaired lung function and contributes to the development of chronic lung diseases.