[Effects of electronic cigarettes on health: a systematic review of the available evidence.]

In recent years there has been an enormous development in the use of electronic cigarettes (e-cig). In Italy, in the 2019, the users of e-cig are about 900.000. E-cig users tend to overlook the absolute risk of the e-cig product in favor of the relative risk compared to traditional ones. This is also due to the fact that at the moment there are large knowledge gaps on the health effects of using e-cig. Recently reports have emerged regarding serious health adverse effects (AE) related to their use. As of December 2019, the American Centers for Disease Control and Prevention (CDC) reported 2409 cases of lung disease associated with the use of e-cig, and 52 deaths.

To summarize the available evidence on the health effects of electronic cigarettes.

We searched systematic reviews (SR) of the literature published up to September 2019.

The systematic searches led to the identification of 14 SRs (1037 studies included of which 77 provided useful information for this review) that met the inclusion criteria. Given the heterogeneity of the comparisons and of the outcome measures considered, the results are described narratively. Effects on the respiratory system: cough, phlegm, asthma and bronchitis symptoms, cases of chronic bronchitis and COPD have also been reported. Effects on the oropharyngeal system: lesions in the oral cavity, villous black tongue, allergic reactions, endogenous formation of carcinogens, development of oral cancer. Effects on the cardiovascular system: increased heart rate, increased systolic and diastolic pressure. Effects on skin and annexes: squamous and pruritic dermatitis. Any adverse effect: the most frequently reported AEs are cough, dry mouth, shortness of breath, irritation of the mouth and throat and headache. Effects of exposure to e-cig passive smoking: increase in cotinine levels in exposed environments.

These results, based on evidence from very low to moderate, show a series of possible risks linked to the use of e-cig. However, there is a need for further well-conducted studies with longer follow-up periods to confirm these results.