# Evidence update on the respiratory health effects of vaping e-cigarettes: A systematic review and meta-analysis

## TL;DR

This study finds that vaping e-cigarettes is linked to increased respiratory symptoms and risks compared to never using them, but the evidence is not always strong.

## Contribution

The study provides updated evidence on respiratory health effects of vaping through a systematic review and meta-analysis up to 2024.

## Key findings

- Non-smoker vapers had higher risk of respiratory symptoms compared to never users.
- Dual users had similar COPD risk to non-vaper smokers.
- Evidence for vaping-related lung injury was not significant.

## Abstract

In this review, we aimed to explore whether nicotine e-cigarette or vaping product use impact respiratory health.

We searched CINAHL, Embase, MEDLINE, PsycINFO, PubMed and Cochrane library databases initially in January 2023 and updated the search in January 2024. We included peer-reviewed human, animal, cell/in vitro original studies published between July 2021 and December 2023 but excluded qualitative studies. Three types of e-cigarette exposure were examined: acute, short-to-medium term, and long-term.

We included 119 studies in the main analysis, and 5 in meta-analysis. Over half of the studies had low risk of bias. Non-smoker current vapers had higher incident risk of respiratory symptoms (relative risk, RR=1.90; 95% CI: 1.28–2.83) but statistically non-significant risk of chronic obstructive pulmonary disease (COPD) (RR=2.53; 95% CI: 0.96–6.67) compared to never users. They also had lower incident risk of respiratory symptoms compared to non-vaper current smokers (RR=0.75; 95% CI: 0.64–0.89) and dual users (dual use vs vaping, RR=1.26; 95% CI: 1.03–1.55). Dual users had higher risk of incidence of respiratory symptoms and prevalence of COPD compared to never users (RR=2.53; 95% CI: 1.44–4.45 and RR=3.86; 95% CI: 1.49–10.02, respectively), and the risk was statistically similar to non-vaper current smokers (RR=0.97; 95% CI: 0.84–1.14 and RR=1.15; 95% CI: 1.00–1.33, respectively). All meta-analysis findings were of ‘very low’ to ‘low’ certainty evidence. Of the studies not included in meta-analysis, we found ‘moderate’ certainty evidence of higher risk of respiratory symptoms, COPD, asthma, lung inflammation and damage in non-smoker current vapers compared to non-users, inconsistent findings on the risk of COVID-19 and other respiratory infections, and no significant association with e-cigarette associated lung injury.

E-cigarettes are associated with harms to the respiratory system. Further longitudinal research with special attention to measuring effects in different e-cigarette user populations are warranted.