Abstract
Background:Smoking is uniquely deadly, with its associated morbidities and mortalities felt most among people who face inequalities, especially those with mental health conditions (MHC). Tobacco smoke contains hundreds of known toxicants, exposure to which can be estimated by measuring Biomarkers of Exposure (BoE) in bodily fluids such as urine. People with MHCs who smoke are known to smoke more heavily and be more dependent than people without MHCs, with a ‘dose response’ relationship according to the severity of the MHC. However, there is little research on their vaping prevalence and characteristics, such as device type and nicotine concentration. Moreover, there is little evidence on whether people with and without MCHs are exposed to different levels of toxicants than people without MHCs due to differing smoking and vaping characteristics.
Aims:
i)To assess levels of toxicant exposure in people who vape compared to smoke, or neither smoke nor vape. ii)To investigate smoking and vaping characteristics (e.g. product type) among people with a single or multiple MHC compared to those without an MHC. iii)To explore the levels of BoE among people with MHC who vape compared to smoke, or neither smoke nor vape.
Methods:
Five studies were conducted. For aim i), a systematic review and meta-analysis of levels of tobacco specific nitrosamines (TSNAs), and a systematic review and meta-analysis of polycyclic aromatic hydrocarbons (PAHs), metals, and volatile organic compounds (VOCs) were conducted. For aim ii), data were drawn from 27,437 adults from the Smoking Toolkit Study (STS) in Great Britain, surveyed between 2020 and 2022. Multinomial regressions analysed associations between smoking, vaping and dual use prevalence, smoking/vaping characteristics and (a) history of a single or multiple MHC and (b) moderate or serious psychological distress. For aim iii), two studies were conducted. First, data were from 5570 adults (aged 18+) from Wave 5 (2018) biomarker dataset of the US Population Assessment of Tobacco and Health (PATH) study. Regression models were used to explore associations between Experience of Psychosis (EoP), smoking/vaping status and levels of BoE of toxicants (nicotine, TSNAs, metals, VOCs). Second, a feasibility and acceptability study was conducted among people who vaped, smoked, dual used (vape and smoke), used Nicotine Replacement Therapy (NRT), or did not use any nicotine or tobacco from inpatient psychiatric services in South London. Smoking and vaping data and urine samples were collected twice, with one month between collection and analysed for levels of BoE (nicotine, PAHs, metals, VOCs).
Results
Aim i) Of 12,781 identified studies, 22 were included for TSNAs. Of 13,867 identified studies, 29 were included for PAHs, metals and VOCs. TSNAs. Longitudinal studies (12 for TSNAs, 7 for PAHs, 11 for VOCs) consistently reported significant reductions in levels of TSNAs, PAHs and VOCs when people switched from smoking to vaping.
Nine cross-sectional studies also reported significantly lower levels of TSNAs, PAHs and VOCs among people who vaped compared to people who smoked. However, comparisons between people who vaped and people who neither vaped nor smoked were inconsistent. Across the two longitudinal and ten cross-sectional studies that reported levels of metals, comparisons between people who vaped, smoked or neither vaped nor smoked were inconsistent.
Aim ii) Compared with people who had never smoked, those who currently smoked and or vaped were more likely to report a history of a single or multiple MHCs and/or moderate or serious past month psychological distress. Smoking roll-your-own cigarettes and smoking more heavily were associated with a history of single or multiple MHCs. There were no associations between vaping characteristics and history of MHCs, but the frequency of vaping, device type and nicotine concentration differed by psychological distress.6
Aim iii) Data from PATH found that compared to people without EoP, people with EoP were found to have significantly higher levels of nicotine metabolites, TSNAs, uranium and cadmium and most VOCs. When smoking, vaping and cannabis use were adjusted for, associations between many toxicants and EoP became non-significant. Interactions between smoking/vaping status and EoP indicated that people with EoP who vaped had higher levels of nicotine exposure and some VOCs than people without EoP who vaped. Moreover, levels of certain metals and VOCs were significantly higher among people with EoP who smoked compared to people without EoP who smoked. The feasibility and acceptability study found that the methods employed were feasible and acceptable, but I was unable to recruit people who exclusively smoked or used NRT. People who vaped or dual used had similar levels of urinary nicotine and cadmium, which were higher than people who neither vaped nor smoked. People who dual used had significantly higher levels of VOC compared to people who vaped or neither vaped nor smoked.
Conclusions
People who vaped had lower levels of BoE (TSNAs, PAHs and VOCs) than people who smoked, whereas levels of metals were inconsistent across the two groups. Findings for people who vaped compared with people who neither vaped nor smoked were inconsistent across all the BoE. Overall, people with MHCs smoked and/or vaped more than people without MHC, resulting in higher levels of BoE in this population. However, among those who smoked and/or vaped with MHC, BoE levels were generally similar to people without MHCs. Moreover, relative (vaping vs smoking) and absolute (vaping vs neither vaping nor smoking) comparisons were generally comparable among people with and without MHCs. Findings did indicate that differences in vaping and smoking characteristics may result in higher exposure to nicotine, some metals and some VOCs among people with MHCs. This warrants further exploration, especially using larger sample sizes for the UK, as these findings may be due to small sample sizes or because samples were drawn from the US, where different products are available.
| Date of Award | 1 Jun 2024 |
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| Original language | English |
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| Supervisor | Ann McNeill (Supervisor) & Deborah Robson (Supervisor) |