A new review conducted on the available scientific literature showed no difference in respiratory parameters in human clinical tests on the respiratory effects of ENDS use in participants who smoke tobacco cigarettes

Catania, 8 November, 2023 – The substitution of electronic nicotine delivery systems for tobacco smoking can be a valid solutions in harm reduction strategies. For those seeking the final goal of a complete nicotine cessation but who are not able to quit abruptly, using reduced risk products may improve their health condition while reducing the harm caused by smoking.

However, in order to give people who smoke relevant and reliable scientific data, is essential to evaluate what are the effects on health of e-cigarette substitution.

The In Silico Science team, led by dr. Renée O’Leary, set new standards for an effective scientific literature review: after having published a new protocol for umbrella review, the team started investigating what are the data on health respiratory results in studies analyzing ecig substitution.

In their work “Respiratory health effects of e-cigarette substitution for tobacco cigarettes: a systematic review”, researchers analyzed 16 studies from 20 publications: most of the studies showed no difference in respiratory parameters. This indicates that electronic nicotine delivery systems substitution for smoking likely does not result in additional harm to respiratory health.

We used a comprehensive approach” explained dr. O’Leary “We conducted a tabular synthesis by study design, population, test measurements, and biases. No significant differences were reported in 43 tests between e-cigarette use and cigarette use”.

The review included 5 studies from Greece, 4 from the United Kingdom, 3 from the USA, 2 from Italy and 1 each from Belgium and Hungary. The participants ranged in age from 18 to 73, comprising 1,357 participants who smoked. 6 studies included participants with asthma or chronic obstructive pulmonary disease (COPD). 9 studies presented follow-up data ranging from 5 days to 5 years: they found improvements in some lung function tests.

Findings on the respiratory health effects of ENDS substitution for smoking varied by health status and by the duration of ENDS use. For participants without respiratory disease, the acute studies did not show a clinically meaningful worsening of pulmonary function with ENDS use. Four acute and five short-term studies recorded no changes in healthy participants using ENDS. 

“One of the problems found during our evaluation is that many studies were not of sufficient duration for observing  any harmful or positive effects because these may take time to manifest. Symptoms reduction may even take longer for patients with specific respiratory diseases. We urgently need long term studies and, above all, a good quality research design”.

In fact, the researchers observed a general low quality of the studies included in the review with ten of sixteen studies rated at high risk of bias. 

In addition, the In Silico Team evaluated cases of reporting bias in the studies. This occurs when the study authors manoeuvre their discussion only to sources that conform to their desired conclusions. Another example is when authors unevenly highlighted one side of their study with the framing effect of language that focused on the loss of health or risks. In some studies, the authors were unjustified in stating that their findings showed an effect when the data were not statistically significant, meaning that there was no change in outcome with e-cig use.. 

In light of the findings of no change in respiratory function plus the presence of reporting spin bias, the In Silico researchers call for long term studies that include diverse participants and to assess smoking behavior and history. Furthermore, they note that exclusive ENDS use and dual use with cigarettes should be identified as separate categories for analysis and findings.

Qureshi, M.A., Vernooij, R.W.M., La Rosa, G.R.M. et al. Respiratory health effects of e-cigarette substitution for tobacco cigarettes: a systematic review. Harm Reduct J 20, 143 (2023). https://doi.org/10.1186/s12954-023-00877-9