Second-hand smoke exposure linked to Alzheimer's risk

This is Your Brain on Smoke

Within the first five minutes, your the aorta begins to stiffen. And you really don’t want that because the aorta needs to be flexible in order to drive freshly oxygenated blood from the heart to your entire body.

But just five minutes after exposure to second-hand cigarette smoke, your aorta loses some functionality. And that’s just the beginning of the bad news.

About 30 minutes later, if you’re still inhaling second-hand smoke, your blood actually starts to get “sticky” with activated blood platelets. At this point, blood vessel dilation is reduced and damage to artery linings begins.

Within two hours your heart rhythm may become disturbed. You never lit a cigarette, you might never have smoked a cigarette in your life, but the sad fact is that you’re essentially a smoker if you regularly inhale second-hand smoke.

Years later, your brain suffers the final indignity from all that smoke.

Spit take

When you inhale cigarette smoke, your body metabolizes nicotine and produces a chemical called cotinine. So concentrations of cotinine provide an effective way to get an idea of how much smoke is actually being inhaled by a passive smoker.

University of Cambridge researchers measured saliva cotinine levels in more than 4,800 non-smoking subjects, then divided the subjects into four groups, from highest to lowest cotinine concentrations. Each subject was also given neuropsychological tests to judge cognition and brain function.

Results: Highest cotinine levels were associated with the poorest cognitive test scores. And as cotinine levels dropped, test scores significantly improved.

The Cambridge team believes that theirs is the first study to compare cognitive function with second-hand smoking. But the results aren’t entirely surprising because smoking is closely linked to cardiovascular risks, and narrowing of arteries is one of the known causes of dementia. In fact, vascular dementia is the most common form of dementia after Alzheimer’s disease.

Protecting heart and brain

In a healthy person, the endothelial cells that line the heart and blood vessels release nitric oxide (NO). But when smoking or exposure to second-hand smoke damages the endothelium, NO production is decreased and blood vessels become less responsive to changes in blood flow.

Studies have shown that foods containing flavanols may increase bioactive NO in the blood. (Flavanols are antioxidant and anti-inflammatory chemicals that give some fruits and vegetables their color.) In a 2005 study, German researchers showed that blood vessel response improved and NO levels increased significantly in a cohort of smokers who were given a flavanol-rich cocoa drink. Apples, broccoli, onions, various berries, tea and wine all supply good amounts of flavanol.

And in the e-Alert “Reality Double Check” (8/24/05), I told you about a study from the University of California, Berkeley (UC) that examined the effects of vitamin C and other nutrients on oxidative stress in 67 middle-aged nonsmokers who were regularly exposed to second hand smoke.

Split into three groups, the subjects were given either 500 mg of vitamin C daily; a mix of vitamin C, E, and alpha-lipoic acid; or a placebo. After two months, researchers found that, compared to the placebo group, the vitamin C group showed a decrease in oxidative stress of more than 11 percent, and the nutrient mix group of almost 13 percent.

A 13 percent reduction in oxidative stress is far from a guarantee you’ll avoid a heart attack triggered by passive smoking, but when the heart and brain are exposed to second- hand smoke any margin of safety is welcome.

Sources:
“Exposure to Secondhand Smoke and Cognitive Impairment in Non-Smokers: National Cross Sectional Study with Cotinine Measurement” British Medical Journal, Published online ahead of print 2/12/09, bmj.com
“Acute Consumption of Flavanol-Rich Cocoa and the Reversal of Endothelial Dysfunction in Smokers” Journal of the American College of Cardiology, Vol. 46, 9/10/05, content.onlinejacc.org
“Vitamin C Supplementation Decreases Oxidative Stress biomarker f2-Isoprostanes in Plasma of Nonsmokers Exposed to Environmental Tobacco Smoke” Nutrition and Cancer, 2003; 45(2), 176-84, ncbi.nlm.nih.gov