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Secondhand Smoke Linked to Dementia

New research from Hong Kong reports changes in the brains of rats which were regularly exposed to smoky air.
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With frustrating vagueness reflecting the limitations of our knowledge, the Mayo Clinic website reports Alzheimer’s disease is caused by “a combination of genetic, lifestyle and environmental factors.” Newly published research provides evidence that one of those environmental factors may be secondhand cigarette smoke.

Researchers in Hong Kong report chronic exposure to smoky air apparently affected the brains of rats. “These changes might serve as evidence of early phases of neurodegeneration,” they write in the online journal PLoS ONE, “and may explain why smoking can predispose brains to Alzheimer’s Disease and dementia.”

Echoing the conclusions of a 2008 study from England, a 2010 paper published in the American Journal of Epidemiology reported a link between lifetime exposure to secondhand smoke and an increased risk of dementia, at least in certain elderly individuals. A research team led by Yuen-Shan Ho of the University of Hong Kong’s Laboratory of Neurodegenerative Diseases used male Sprague-Dawley rats to try to determine the medical reasons underlying this linkage.

The researchers conducted an experiment using nine rats, each of which spent one hour per day for 56 days in a specially ventilated chamber. For five of the rodents, the air in the chamber had a smoke concentration of 4 percent. This mimicked “the situation of humans in restaurants or bars were cigarette smoking is permitted,” the researchers write.

Compared to the rodents who breathed clean air, “Many abnormalities were observed in the hippocampus in the smoking-exposed rats,” they report. “These changes collectively may have an impact in normal cellular function.”

“Our data suggested that daily exposure to cigarette smoke could accelerate the aging of the brain,” the researchers write. Specifically, they report that ongoing exposure to smoke appeared to alter the proteins that allow proper functioning of the synaptic system, which plays an essential role in our ability to form and hold onto memories.

“Our study demonstrated that exposure to cigarette smoke could induce pathological changes in the brain,” they conclude, “and these changes might make us more susceptible to the development of cognitive impairment, or even Alzheimer’s disease, late in life.”

So while that job as a bartender or cocktail waitress at a smoke-filled establishment may be temptingly lucrative, the long-term price you pay could be enormous—even if you don’t get cancer.