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Hookah smoking impairs blood vessel function

Smoking hookah tobacco acutely impairs the ability of blood vessels to function, according to preliminary research presented in Chicago at last month's American Heart Association’s Scientific Sessions 2018, a premier global exchange of the latest advances in cardiovascular science for researchers and clinicians.

Hookah, also known as a waterpipe, consists of a bowl, a chamber partially filled with water, hose and mouthpiece. It is designed to burn specialty tobacco which is typically fruit or candy-flavoured.

Hookah is often marketed as a harmless alternative to cigarettes. However, while studies have shown cigarette smoking damages endothelial function (thin membrane lining the inside of the blood vessel), little is known about how smoking flavoured hookah tobacco impacts on blood vessels.

“Hookah is the only form of tobacco product that uses burning charcoal briquettes to heat the flavoured tobacco in the waterpipe. So, in addition to toxic substances from tobacco and nicotine, hookah smoke exposes users to charcoal combustion products, including large amounts of carbon monoxide,” said Dr Mary Rezk-Hanna, study lead author and assistant professor at the University of California – Los Angeles School of Nursing.

In a collaborative research study between the University of California – Los Angeles School of Nursing; University of California San Francisco School of Medicine; and the Smidt Heart Institute at Cedars-Sinai Medical Centre, Rezk-Hanna and colleagues studied 30 young adult (average age 26) hookah smokers before and after charcoal-heated hookah smoking.

They measured nicotine levels in blood, exhaled carbon monoxide and flow-mediated dilation of blood vessels (a measure of endothelial function). In 20 participants, they took the same measurements before and after electrically heating the same hookah flavoured tobacco product. They also compared results to similarly aged cigarette smokers after smoking one cigarette. Finally, they took the same measurements before and after a group of hookah smokers breathed a carbon monoxide gas mixture to mimic the carbon monoxide boost they get from smoking traditional charcoal-heated hookah.

They found that while nicotine levels increased similarly with all smoking products, exhaled carbon monoxide increased 9- to 10-fold with charcoal-heated hookah smoking compared to electronically-heated hookah or cigarette smoking. While charcoal-heated hookah smoking increased flow-mediated dilation, smoking electrically-heated hookah tobacco or cigarette tobacco similarly and substantially decreased flow-mediated dilation (indicating impairment of endothelial function).

The key difference between charcoal and electrically-heated hookah or cigarette tobacco smoking is the production of high levels of carbon monoxide from charcoal briquettes. Carbon monoxide is known to dilate blood vessels and appears to mask the effects of charcoal-heated hookah tobacco smoke to impair endothelial function, according to Rezk-Hanna.

These findings suggest that hookah tobacco smoking, like cigarette tobacco smoking, impairs blood vessel function. The authors conclude that hookah use, either charcoal or electrically-heated, may impair other aspects of endothelial functions, which are critical for cardiovascular health.

Hookah smoking is effectively marketed to youth as a harmless alternative to cigarettes. While cigarette smoking acutely impairs endothelial function, the effect of smoking flavored hookah tobacco is unknown. Because charcoal traditionally is used to heat the hookah tobacco, 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 carbon monoxide (CO), a putative endothelial-dependent vasodilator molecule. To test the net acute effect of hookah smoking on brachial artery flow-mediated dilation (FMD), in young adult hookah smokers (n=30, age 26±1 years, mean ±SE), we measured plasma nicotine, exhaled CO, and FMD before and after charcoal-heated hookah smoking. To remove the effect of charcoal combustion, the same measurements were performed when the same hookah flavored tobacco product was heated electrically (n=20). As a positive control, we studied age-matched cigarette smokers (n=15) who smoked one cigarette. Nicotine levels increased similarly with all types of smoking, while 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. To isolate the effect of the CO boost on FMD, hookah smokers (n=8) inhaled a 0.1% CO gas mixture. FMD increased markedly by 125±15% (p<0.001) after breathing CO gas—2.9 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 vs. 25±4 PPM). Thus, we conclude that smoking hookah tobacco, like 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 endothelial-dependent vasodilator molecule generated by charcoal combustion. With respect to large artery endothelial function, smoking hookah is not harmless.

Mary Rezk-Hanna, Zab Mosenifar, Neal Benowitz, Mohamad Rashid, Katherine Davoren, Norma P Moy, Charles Yoou, Lynn Doering, Wendie Robbins, Linda Sarna, Robert M Elashoff, Ronald Victor

[link url=""]AHA material[/link]
[link url=""]Circulation abstract[/link]

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