Limitation 1: Long-Term Health Effects Unknown
The review assessed smoking cessation outcomes, not long-term health effects of vaping. While the review notes that adverse events were generally low and similar between vape and NRT groups in the short term, it explicitly states that long-term health effects of e-cigarette use remain uncertain. The longest follow-up in the included studies was 2 years — far shorter than the decades-long health effects documented for combustible cigarettes.
Limitation 2: Study Heterogeneity
The 91 studies used different devices (cigalikes, vape pens, pod systems), different nicotine concentrations, different support intensities, and different control conditions. This variability makes it difficult to say which device type, nicotine strength, or support combination works best. The review pools all nicotine vapes together — it cannot tell you whether a specific pod system performs better than a specific NRT patch.
Limitation 3: Funding and Conflicts
Some studies in the review received funding from e-cigarette manufacturers or had investigators with industry ties. The Cochrane authors note this and conduct sensitivity analyses, but readers should be aware that industry-funded studies tend to show more favorable results than independently funded ones.
Limitation 4: Generalizability to Real-World Settings
Most RCTs provide structured support (counseling, check-ins, device instructions) that exceeds what most adults attempting to quit in the real world receive. Quit rates in clinical settings may overestimate what happens when someone buys a vape at a convenience store and tries to quit on their own.
