Vaping linked to higher COPD risk, meta-analysis finds

By Vijay Kumar MalesuReviewed by Susha Cheriyedath, M.Sc.Jul 8 2025

Researchers find that both current and former e-cigarette users face elevated odds of chronic lung disease, raising new questions about the long-term safety of vaping.

Review: Association of electronic cigarette use and risk of COPD: a systematic review and meta-analysis. Image Credit: Vitaliy Abbasov / Shutterstock

In a recent review published in the journal npj Primary Care Respiratory Medicine, a group of researchers quantified the relationship between electronic cigarette (e-cigarette) use and the odds of developing chronic obstructive pulmonary disease (COPD) across observational studies.

The majority of included studies were from the United States, with only single cohorts from China and South Korea, which may limit the generalizability of findings to other global populations.

Background

Every 4 seconds, someone worldwide dies from COPD, a progressive airflow-limiting illness once blamed almost exclusively on burning tobacco. Now e-cigarette devices, formally called Electronic Nicotine Delivery Systems (ENDS), have flooded markets, promising a safer inhale but generating an aerosol rich in ultrafine particles, aldehydes, and metals.

Public health officials face a dilemma: can vaping curb combustible smoking without seeding a new wave of COPD? Epidemiological signals are emerging, yet findings remain inconsistent and often confounded by dual use. Clarifying this relationship is vital for clinicians, policymakers, and millions of vapers; therefore, rigorous evidence is needed.

About the study

The investigators conducted a systematic review and meta-analysis, adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, and registered the protocol in the International Prospective Register of Systematic Reviews (PROSPERO).

The researchers systematically searched PubMed, Embase, and Web of Science from their inception to 15 February 2024, pairing e-cigarette synonyms with COPD descriptors. They included observational studies of adults that categorized e-cigarette exposure as current, former, or ever use and reported relevant effect estimates, such as Odds Ratio (OR), Risk Ratio (RR), Hazard Ratio (HR), or Incidence Rate Ratio (IRR), for COPD.

Reviewers independently screened records, extracted data through the Nested-Knowledge platform, and judged quality with the Newcastle-Ottawa Scale (NOS). Random-effects meta-analysis in R version 4.4 was used to pool log-transformed effect sizes, and statistical heterogeneity was quantified using the I² statistic.

Leave-one-out and predefined sensitivity analyses restricted to spirometry-confirmed diagnoses or high-quality (NOS ≥ 7) studies tested accuracy. Subgroup analyses contrasted cross-sectional with cohort designs. All risk estimates were harmonized to ORs for comparability before pooling. Potential publication bias was visually inspected using a funnel plot and formally assessed with Egger’s regression test. A two-sided P-value below the 0.05 threshold denoted significance throughout.

Study results

Seventeen studies meeting all inclusion criteria contributed data on over 4.3 million adults drawn mainly from the United States, with single cohorts from China and South Korea. Twelve investigations were cross-sectional, and five were longitudinal; sample sizes ranged from 8,087 to over 705,000 participants.

While two cohorts confirmed COPD by spirometry, using the Forced Expiratory Volume in 1 second to Forced Vital Capacity (FEV1/FVC) ratio, fifteen studies relied on self-reported physician diagnosis, which may introduce misclassification bias. Quality scores on the NOS ranged from 5 to 9, with most studies being ranked as moderate to high quality.

After harmonizing estimates to ORs, the pooled analysis revealed that current e-cigarette users had 48% greater odds of COPD than never users (OR = 1.48, 95% Confidence Interval (CI) 1.36–1.61) with no between-study heterogeneity (I² = 0%).

Former users showed the largest relative excess: 84% higher odds (OR = 1.84, 95% CI 1.51–2.23), albeit with moderate inconsistency (I² = 56%). Individuals who had ever experimented with e-cigarettes, regardless of current status, still carried 79% higher odds (OR = 1.79, 95% CI 1.42–2.25) and again exhibited negligible heterogeneity (I² = 0%).

Notably, all studies assessing ever-e-cigarette users in this meta-analysis adjusted for age, helping to ensure that the observed association was not simply due to age differences. Subgroup analysis suggested design-related nuance.

Cross-sectional investigations indicated a stronger link for current e-cigarette use (OR = 1.592, 95% CI 1.349–1.879) than cohort investigations, whose summary estimate dropped to 1.145 (95% CI 0.842–1.557) and spanned unity, suggesting limited longitudinal support. Yet the design-based contrast test failed to reach statistical significance (P = 0.06).

Robustness assessments affirmed stability: removing each study in turn shifted pooled OR values by under three percentage points, and restricting the pool to high-quality articles (NOS ≥ 7) preserved significant associations for current (OR = 1.56, 95% CI 1.07–2.25) and former users (OR = 2.57, 95% CI 1.91–3.46).

Conversely, limiting the analysis to the two spirometry-verified cohorts diminished the link and rendered it non-significant (OR = 1.14, 95% CI 0.82–1.58), highlighting that the association is less robust when only objective COPD diagnoses are used.

Publication bias appeared unlikely; the funnel plot was symmetrical, and Egger’s regression yielded P = 0.1449. It is important to note that these findings are associations from observational studies and do not establish causality. For context, traditional cigarette smoking remains a much stronger risk factor for COPD, with prior meta-analyses reporting odds ratios of approximately 3.5 for current smokers compared to never smokers.

Translating percentages to people, the authors did not directly calculate the proportion of COPD cases attributable to vaping; such interpretations should be made with caution.

Conclusions

To summarize, the aggregated evidence indicates that e-cigarette exposure is associated with greater odds of COPD, even after accounting for study quality, smoking history, and analytic approach. Current vapers face a roughly 50% increased risk, while former users retain an even larger burden.

However, causality cannot be inferred, and the observed associations may be influenced by confounding factors, such as the dual use of combustible tobacco and a prior smoking history. Clinicians should inquire about vaping, counsel on cessation, and monitor lung function, particularly in younger adults who might otherwise be overlooked.

Policymakers must balance any smoking-cessation benefits against the emerging respiratory toll and support longitudinal research to clarify causality. Further studies with objective COPD diagnoses, careful adjustment for smoking status, and detailed assessment of duration and intensity of e-cigarette use are needed to clarify the long-term impact of vaping on respiratory health.