Importance: The rising use of nicotine vapes among young adults who have never smoked combustible tobacco raises concerns regarding potential early cardiovascular and respiratory effects in an otherwise low-risk population. Objective: To determine whether regular daily nicotine vape use is associated with altered vascular function and cardiorespiratory fitness in young adults without established cardiovascular risk factors. Design, Setting, and Participants: This was a cross-sectional, single-center, laboratory-based physiological assessment study conducted between July 2023 and April 2025 among young adults without known cardiovascular disease or major risk factors. Based on self-report and verification of smoking status, participants were stratified into 3 groups: adults who exclusively used nicotine vapes, adults who used combustible cigarettes, and tobacco- and nicotine vape-naive individuals. Data analysis was performed from September 2023 to April 2025. Exposure: Regular daily use of nicotine vapes or combustible cigarettes. Main Outcomes and Measures: Primary outcomes included vascular function, assessed by flow-mediated dilation (FMD) and carotid artery reactivity (CAR), and cardiorespiratory fitness, assessed through ventilatory, metabolic, and cardiac responses during maximal cardiopulmonary exercise testing. Secondary measures included spirometry results and physical activity. Results: Fifty-eight young adults (mean [SD] age, 26 [7] years; 30 [52%] female) were included, among whom 17 exclusively used nicotine vapes, 19 used combustible cigarettes, and 22 were tobacco and nicotine vape naive. Lung function and physical activity levels did not differ significantly across groups. FMD and CAR were lower both in adults who used nicotine vapes (mean [SD] FMD, 5.5% [3.4%]; mean [SD] CAR, 0.6% [5.3%]) and in adults who used combustible cigarettes (mean [SD] FMD, 4.4% [2.9%]; mean [SD] CAR, -1.4% [5.3%]) compared with tobacco- and nicotine vape-naive individuals (mean [SD] FMD, 8.3% [3.4%]; mean [SD] CAR, 4.7% [3.2%]). Peak oxygen uptake was lower in adults who used nicotine vapes compared with tobacco- and nicotine vape-naive individuals but did not differ significantly between combustible cigarette and naive groups; minute ventilation and cardiac output were lower in both nicotine use groups. Conclusions and Relevance: Regular daily nicotine vape use in young adults who have never smoked combustible tobacco was associated with lower vascular function and cardiorespiratory fitness. These findings highlight the need for longitudinal studies to determine long-term clinical implications.
Regular daily nicotine vape use in young adults who have never smoked combustible tobacco was associated with lower vascular function and cardiorespiratory fitness.
small cross-sectional groups and a below-100-cigarette eligibility allowance limit the broad never-smoked and fitness framing
Adults who used nicotine vapes and combustible cigarettes exhibited lower FMD and CAR compared with nicotine-naive individuals
cross-sectional vascular comparisons support the direction, although small groups and residual confounding limit interpretation
Peak relative V̇O$_{2}$ was lower only in the group with nicotine vape use compared with tobacco- and nicotine vape-naive individuals, but not in the group with combustible cigarette use.
the reported relative-uptake comparison supports this association, but small cross-sectional groups and differential CPET exclusions limit certainty
Derived from the full evaluation — not a separate score.
Strengths
The study compares exclusive vapers, combustible-cigarette users, and nicotine-naive participants using both vascular testing and maximal exercise testing, extending the scope of the cited prior CPET comparison.
↳ Methods; Tables 2–3; Discussion, Cardiorespiratory Response to Exercise
FMD, carotid reactivity, spirometry, and CPET follow established protocols. Objective activity measurement, adjusted vascular analyses, and a restriction to vapers without combustible-cigarette history provide additional checks on the associations.
↳ Methods; Results, Vascular Function
The discussion includes positive and null endothelial findings and explains why smoking-cessation trials with substantially heavier smoking histories are not directly comparable.
↳ Discussion, Vascular Function
Limitations
The Discussion claims lower relative peak oxygen uptake in vapers than in combustible-cigarette users, although Table 3 establishes no significant difference between those groups. Table 1 also reports 19 cotinine-positive vapers in a group of 17.
↳ Discussion, Cardiorespiratory Response to Exercise; Tables 1 and 3
The cross-sectional design cannot establish that vaping adversely affects vascular health. Nonsignificant differences between small nicotine-use groups also do not demonstrate equivalent impairment.
↳ Discussion, Vascular Function; Conclusions
Five participants were excluded from CPET, comprising three naive participants and two vapers, without a reported sensitivity analysis of those exclusions. Numerous outcomes and incompletely measured confounders add uncertainty to the small-group comparisons.
↳ Results, Respiratory Function and Cardiorespiratory Response to Exercise; Statistical Analysis; Limitations
The combined vascular and exercise-testing design provides an informative physiological comparison across three exposure groups. Standardized measurement and adjusted analyses support the association question, but small samples, multiple outcomes, and differential CPET exclusions leave meaningful uncertainty. The Discussion's causal language and the inference of similar impairment go beyond what these comparisons establish. Engagement with conflicting studies and explicit restrictions on clinical interpretation support the contextual assessment, while the contradictory oxygen-uptake statement and impossible cotinine count require correction.
Nabu’s assessment, alongside the field’s view.
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Confidence mediumThe three-group comparison combines vascular measures with criterion-standard CPET and adds a combustible-cigarette comparator to prior exclusive-vaper fitness work. Its advance remains incremental because small cross-sectional groups cannot establish causal harm or equivalence between nicotine-use groups.
Standardized physiological protocols, matching, activity measurement, adjustment, and restriction analyses support the association question, but the causal Discussion assertion binds the score at 2.8. Differential CPET exclusions and multiple outcomes add uncertainty, while the contradictory oxygen-uptake statement and exposure-verification reporting remain separately visible through the reliability flag.
The paper's organization and associative headline make its main argument followable. Contradictory oxygen-uptake wording, the pack-year attribution error, and inconsistent causal phrasing reduce precision without making the overall argument incoherent.
The discussion engages positive and null endothelial studies and distinguishes low-smoking-burden participants from heavier-smoking switching-trial populations. Explicit interpretive restrictions support the score, although the challenge to reduced-harm claims conflicts with that otherwise qualified treatment.
Caveats4 of 4 checks
4 reported values do not reconcile, but the key claims do not rest on them.
Ethics approval, written consent, funding, and conflicts are disclosed. Carotid-diameter units and the reported respiratory-exchange-ratio dispersion require clarification.
Conflict of interest: declared · Ethics approval: declared · Data availability: declared
44 references in manuscript 41 of 41 checkable references found in an index 3 are books, websites or datasets — counted, but not index-checkable
References not verified automatically are resolved manually within 24 hours.
No retraction or expression of concern found in Crossref (includes Retraction Watch).
Sources: Crossref (incl. Retraction Watch) ✓
Where this paper’s evidence sits on the path from initial observation to real-world use.
The physiological associations can motivate longitudinal research and inform cautious communication. They do not establish persistent injury, clinical risk, or an intervention effect.
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