Nicotine absorption from e-cigarettes over 12 months

Background

Research indicates that, over time, exclusive e-cigarette users (vapers) gradually reduce the nicotine concentration in their e-liquid and transition to more sophisticated devices. Alongside this, consumption of e-liquid increases and constant cotinine levels are maintained.
Aims

We aimed to confirm these observations in 27 experienced vapers tested at baseline and 12 months later, by measuring nicotine absorption (via salivary levels of the nicotine metabolite cotinine; ng/mL), nicotine concentrations in e-liquid (mg/mL), volume of e-liquid consumed (mL per day), device types and flavours used, both at baseline and 12 months.
Results

Vapers reduced both their nicotine concentrations in e-liquid over 12 months (from 13.83 mg/mL at baseline to 9.91 at follow up) but significantly increased their e-liquid consumption (from 4.44 to 6.84 mL). No significant changes in salivary cotinine concentrations (370.88 ng/mL at baseline and 415.78 ng/mL at follow up) were observed. There was an increase in sub-ohming (using an atomiser coil with resistance of <1 Ω with increased power) at 12 months, and in the use of fruit flavoured e-liquids.
Conclusions

Our sample of experienced vapers reduced the concentration of nicotine in their e-liquid over time, but maintained their nicotine intake possibly through self-titration via more intensive puffing. Findings suggest there may be little benefit in reducing nicotine e-liquid concentration since this appears to result in higher e-liquid consumption which may incur both a financial and health cost. Gaining an understanding of underlying reasons for lowering e-liquid concentration would be a useful line of empirical enquiry.