High Carbon Monoxide Levels from Charcoal Combustion Mask Acute Endothelial Dysfunction Induced by Hookah (Waterpipe) Smoking in Young Adults.

ABSTRACT

BACKGROUND: Hookah smoking is marketed to youth as a harmless alternative to cigarettes. Although cigarette smoking acutely impairs endothelial function, the effect of smoking fruit-flavored hookah tobacco is unknown. Because charcoal traditionally is used to heat the hookah tobacco in the waterpipe, hookah smoke delivers tobacco toxicants and nicotine plus charcoal combustion products not only carbon-rich nanoparticles, oxidants that may destroy nitric oxide and impair endothelial function, but also large amounts of carbon monoxide (CO), a putative vasodilator molecule. METHODS: To test the acute effect of hookah smoking on endothelial function, in young adult hookah smokers (n=30, age 26±1 years, mean±SE), we measured plasma nicotine, exhaled CO, and brachial artery flow-mediated dilation (FMD) before and after charcoal-heated hookah smoking. To remove the effect of charcoal combustion, the same measurements were performed when the same flavored hookah tobacco product was heated electrically (n=20). As a positive internal control, we studied age-matched cigarette smokers (n=15) who smoked 1 cigarette. To isolate the effect of the CO boost on FMD, hookah smokers (n=8) inhaled a 0.1% CO gas mixture to approximate their CO boost achieved with charcoal-heated hookah smoking. RESULTS: Nicotine levels increased similarly with all types of smoking, whereas exhaled CO increased 9- to 10-fold more after charcoal-heated hookah than after either electrically heated hookah or cigarette smoking. FMD did not decrease after smoking charcoal-heated hookah but instead increased by +43±7% ( P<0.001). In contrast, FMD decreased by -27±4% ( P<0.001) after smoking electrically heated hookah, comparable to the decrease after cigarette smoking. FMD increased markedly by 138±71% ( P<0.001) after breathing CO gas, 2.8 times more than the increase induced in the same subjects after smoking charcoal-heated hookah ( P<0.001), despite comparable increases in exhaled CO (24±1 versus 28±3 ppm, hookah versus CO). CONCLUSIONS: Smoking hookah tobacco, similar to cigarette tobacco, acutely impairs endothelial function. With traditional charcoal-heated hookah smoking, the acute endothelial dysfunction is masked by high levels of carbon monoxide, a potent vasodilator molecule generated by charcoal combustion. With respect to large-artery endothelial function, smoking hookah is not harmless. CLINICAL TRIAL REGISTRATION URL https//www.clinicaltrials.gov . Unique identifiers NCT03616002 and NCT03067701.