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E-Cigarette Vapor Does Not Compromise Bone Density, Animal Study Suggests

According to a new study conducted by a team of European scientists, electronic cigarette vapor doesn’t appear to have a negative effect on bone structure, unlike cigarette smoke which significantly decreases both bone density and volume fraction.

We’ve long known that smoking has numerous adverse effects on our health, but apart from the respiratory and cardiovascular functions, most of us can’t really think of other areas where cigarette smoke does serious damage. Our bone system is probably at the bottom of the list of things most of us think are impacted by smoking, but according to a recent study published in the Archives of Toxicology journal, our bone structure can be compromised by smoking tobacco.

The negative effects of smoking on bone structure have been very well documented over the last couple of decades, with both in-vitro and in-vivo studies showing that cigarette smoke compromises bone morphology. Smokers are known to have significantly higher risk of fracture than non-smokers, particularly hip fractures and osteoporotic fractures. However, the effect of e-cigarette vapor on the musculoskeletal system has largely been ignored so far.

Conducted by team of scientists from Eberhard Karls University in Tübingen, Germany, supported by researchers from Philip Morris International laboratories in Neuchatel and Singapore,  this study involved several groups of lab mice exposed to e-cigarette vapor, cigarette smoke and air for a period of six months. At the end of this period, their tibiae were analyzed for bone morphology by CT imaging, biomechanics by three point bending, and histological analysis.

To get a better idea about how electronic cigarette vapor impacts osteogenic cells, the lab mice were exposed to three different types of vapor – ‘Carrier’ (propylene glycol and vegetable glycerin), ‘Base’ (Carrier and nicotine), and ‘Test’ (Base  and flavors). Nicotine level in the nicotine-containing e-liquid was the same as in tobacco cigarettes (35μg/L). This helped researchers figure out if nicotine itself has a negative impact on bone structure, or if the damage is done by other compounds in cigarette smoke.

Mice were exposed for 3 h per day, 5 days per week, for up to 6 months. Intermittent exposure to fresh filtered air for 30 min after the first hour of exposure and for 60 min after the second hour of exposure was provided to avoid accumulation of excessive carboxyhemoglobin in the group exposed to cigarette smoke.

After analyzing the data gathered over the six-month trial, researchers found that none of the e-cigarette vapor formulations that mice had been exposed to had a negative effect on bone integrity, including those containing nicotine and artificial flavors.

On the other hand, exposure to cigarette smoke was shown to have caused a significant decrease in cortical and total bone volume fraction and bone density relative to e-vapor aerosols. Furthermore, subsequent testing also showed a decrease in ultimate load and stiffness.

“Our data revealed a significant decrease in cortical bone structure and strength due to CS (cigarette smoke) inhalation, while inhalation of e-vapor aerosol and its individual components did not cause significant bone changes relative to Sham (air) exposure,” researchers reported.

“In conclusion, because of the bone-preserving effect of e-vapor aerosols relative to CS  exposure, e-vapor products could potentially constitute less harmful alternatives to cigarettes in situations in which bone health is of importance” a PMI Science abstract reads.

The study obviously has its limitations. For one, it was done on mice, not humans, and the rate of exposure over the course of the six-month trial was extreme (at least in my opinion), but the difference in results for cigarette smoke relative to the different formulations of e-liquid aerosols is definitely interesting. Even when exposed to vapor for 3 hours a day, 5 days a week, over six months, analysis showed that the bone structure and density was not significantly affected.

Researchers point out that further testing is necessary to fully understand the effects of e-cigarette vapor and nicotine on the musculoskeletal system, but preliminary findings strongly suggest that they are substantially less harmful than those of tobacco cigarette smoke.

Top photo: Nery Zarat/Unsplash

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