Electronic cigarettes (e-cigarettes or vapes) use a battery to heat a liquid solution (e-liquid) into an aerosol for inhalation. Vaping bypasses the combustion of traditional cigarettes, leading to the perception of reduced harm. Since their market entry in the mid-2000s, use has rapidly increased, particularly among young adults. Studies spanning five years or more are necessary to move beyond acute effects and establish the chronic health implications of sustained exposure.
Scope and Design of Long-Term Vaping Research
Longitudinal cohort studies, often spanning four to eight years, track the long-term health trajectory of vapers. Researchers follow thousands of participants, including exclusive cigarette smokers, those who switched entirely to vaping, and dual users. A major challenge is the rapid evolution of vaping technology, as participants frequently switch devices over the study period. Key parameters tracked include self-reported health outcomes, changes in lung function, and biological markers in the blood related to inflammation and cardiovascular risk.
Studies also analyze patterns of nicotine intake, noting changes in e-liquid concentration over time. Researchers monitor whether former smokers who switch to vaping maintain abstinence from combustible tobacco or relapse. The inclusion of never-smokers who initiate vaping is important for assessing new health risks in an unexposed population. These designs help differentiate the effects of nicotine, base components like propylene glycol, and various flavorings in the aerosol.
Findings Related to Pulmonary Function
Sustained vaping is associated with specific detrimental effects on the respiratory system. A large-scale analysis of nearly 250,000 adults found a significant association between exclusive e-cigarette use and an increased risk of Chronic Obstructive Pulmonary Disease (COPD). This suggests that aerosol inhalation over time damages lung tissue, impeding airflow and causing chronic symptoms. While acute exposure increases airway resistance, long-term data on standard lung capacity measures like forced expiratory volume in one second (FEV1) remain mixed across smaller studies.
The damage pathway differs from smoking because the aerosol contains fewer combustion toxins, such as tar and carbon monoxide. However, e-liquids contain volatile organic compounds and flavorings that become toxic when heated and inhaled. Chemicals like diacetyl, a common buttery flavoring agent, are linked to bronchiolitis obliterans, often called “popcorn lung.” Additionally, the oily nature of some e-liquid components can cause lipoid pneumonia, where fatty substances trigger an inflammatory response in the lungs.
Vaping is also associated with an increased risk of pneumothorax (collapsed lung), particularly in younger individuals. This condition occurs when air collects outside the lung, potentially resulting from the rupture of small air sacs. Even if traditional lung function measures appear stable, persistent exposure to irritants contributes to structural changes and inflammation within the small airways. The full extent of potential issues like lung cancer is still being investigated due to the absence of decades-long data comparable to smoking studies.
Impact on Cardiovascular Health
Five years of vaping significantly impairs blood vessel function, raising concerns about long-term cardiovascular risk. Chronic e-cigarette users exhibit impaired endothelial function, meaning the cells lining the blood vessels are damaged. This impairment is linked to reduced production of nitric oxide (NO), which helps blood vessels dilate and maintain flexibility. Low NO levels promote vessel stiffness and increase the risk for heart conditions.
A sustained increase in blood pressure (hypertension) is also associated with e-cigarette use. Nicotine activates the sympathetic nervous system, contributing to increased heart rate and blood pressure by constricting blood vessels. Even nicotine-free e-liquids can cause vascular dysfunction by increasing oxidative stress, which triggers damage and inflammation within the vascular system.
The serum from chronic vapers causes increased permeability in cultured blood vessel cells. This “leakiness” allows more substances to pass through vessel walls, contributing to systemic inflammation and potentially accelerating atherosclerosis (hardening of the arteries). While the long-term risk of major cardiovascular events is still being established, the documented impairment of endothelial function suggests vapers may face a risk comparable to traditional smokers.
Patterns of Nicotine Dependence
Longitudinal studies demonstrate that vaping is a powerful method of nicotine delivery that establishes and sustains dependence. E-cigarettes deliver nicotine efficiently, especially with newer, high-nicotine salt formulations. For long-term vapers who successfully quit smoking, approximately two-thirds continue using e-cigarettes, replacing one form of dependence with another. This suggests that while vaping is an effective cessation tool for combustible tobacco, it often results in prolonged reliance on nicotine products.
Eight-year data suggest that for a subset of continuous vapers, self-reported nicotine dependence may decrease over time, sometimes accompanied by a switch to lower concentration liquids. However, for populations naive to traditional tobacco, particularly adolescents, e-cigarette use poses a risk as a potential gateway, increasing the likelihood of initiating cigarette smoking. This highlights the challenge of balancing harm reduction for adult smokers with the risk of nicotine addiction among non-smokers.