Effects of Hookah Smoking on Vascular Regulation: Novel Insights into Endothelial Function
Hookah (water pipe) smoking is a major new understudied epidemic of tobacco abuse particularly affecting youth. Hookah’s rapidly growing popularity is due to unregulated expansion of hookah cafes near college campuses and social media marketing to young adults as a safer avant-garde alternative to cigarettes. What distinguishes hookah from all other tobacco products is that burning charcoal is used to heat the tobacco. As a result, hookah smoke delivers a large exposure not only to carbon monoxide (CO), but also to carbon-rich nanoparticles that constitute putative vasoconstrictor stimuli. To determine if hookah smoking acutely impairs endothelial and vascular function, in 23 healthy young adult hookah smokers who do not smoke cigarettes (age 25?5 years, mean?SD; 6 women, 17 men; BMI 23.6?2.3 kg?m2), we measured conduit vessel endothelium-dependent flow-mediated dilation (FMD) by high-resolution ultrasound as well as exhaled CO and plasma nicotine before and immediately after 30 minutes of ad lib hookah smoking in a custom-built smoking chamber. Additionally, we measured micro-vessel endothelial function by way of reactive hyperemia peripheral arterial tonometry (EndoPAT) and central arterial stiffness by carotid-femoral pulse wave velocity (cfPWV). With hookah smoking, exhaled CO increased from 3.5?0.4 to 27?2.4 ppm (mean ?SE, p<0.001 pre-vs. post-hookah), which approximates the CO boost of a typical ad lib hookah smoking session in hookah bars and indicates an exposure to fine and ultrafine particles that is 10 times greater (and to total particles that is 250 times greater) than that with cigarette smoking. The increased heart rate and blood pressure (Δ heart rate +14?2, P<0.001; Δ mean arterial pressure +5?1, P<0.001) were accompanied by increased plasma nicotine (0.6?0.1 to 6.4?1.2 ng/mL, p<0.001). On ultrasound and in contrast to our hypothesis, brachial artery FMD did not decrease with hookah smoking but, surprisingly, increased from 6.9?0.5% to 9.7?0.6%, P<0.001: a 49.6?9.3% relative increase while micro-vessel endothelial function did not change: EndoPAT index 2.08?0.14 to 1.99?0.12, P=0.633). Moreover, cfPWV increased significantly (7.47?0.20 to 8.04?0.22, P<0.001) suggesting central arterial stiffness. Further studies are indicated to elucidate the major underlying mechanisms underpinning the augmented flow-mediated dilation and central arterial stiffness.