Second-Hand Smoke and Memory Loss

In my July 5th column (Is Nicotine Good for Chemo Brain?), I wrote about the nicotine patch. Studies suggest the patch may help with memory loss.
Even though the science is fascinating, I was curious to make sense of why researchers were investigating nicotine as a memory aid when we also know that smoking causes heart disease and cancer. Certainly there had to be something more pure about the patch, otherwise why deal with the devil?
Then I read about two conflicting studies led by Tom Heffernan, PhD at Northumbria University at Newcastle in the UK which showed that cigarettes are detrimental to memory.  In one, he and colleagues found that people who smoke just on weekends not only damage their memory, but cause as much harm as those who smoke everyday. In the other, they concluded that non-smokers exposed to second-hand smoke may suffer impairment in prospective memory (remembering future intentions and activities).

So nicotine on its own boosts memory but cigarettes, which are made of nicotine, destroy it?  Am I the only one here who's confused?  It was time to consult the experts. I decided to email Dr. Heffernan and ask for some clarification. With permission, here's his kind response.  
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Tom Heffernan, PhD
Nicotine administration has been found to have mixed effects on cognition, but overall people in the area feel that it can act as a cognitive enhancer – that is it may boost cognition because it stimulates particular neurotransmitter pathways (for example, the cholinergic system is one of these) which regulate signals around the brain for a range of behaviour/cognition (thinking). This has led some to suggest it can be used to stimulate such systems in people who suffer from mild cognitive impairment (although the authors of the study you cite do stress that much larger clinical trials are needed before the efficacy of transdermal (which means administration through the unbroken skin) nicotine administration can be accurately assessed).

Smoking, on the other hand, not only has nicotine being administered to the smoker, but also has more than 4000 chemicals that have been identified in tobacco smoke, at least 250 of which are known to be harmful and more than 50 of which are known to cause cancer (Source: the World Health Organisation (2009) Report on the global tobacco epidemic). These include: Stearic Acid (Candle wax), Butane (Lighters), Methane (Sewer gas), Arsenic (Poison), Carbon monoxide (Exhaust gas), Methanol (Rocket fuel), Paint, Ammonia (Detergent), Toluene (Industrial solvent), Hexamine (Barbecue starter), Cadmium (Batteries), etc.

So I would suggest that it may well be the toxic mixture of chemicals in the light cigarette that can damage the person’s cardiovascular system and the brain (and therefore resulting in health and cognitive decline).

By the way, second-hand smoking (where a non-smoker receives side stream or direct stream smoke from a smoker in a confined area) does not get the benefit of the nicotine, but does appear to get the harm from the toxic mixture of chemicals. The World Health Organisation has documented evidence of the damage done to children and adults as result of them being exposed to second-hand-smoke in confined areas for prolonged periods of time; And there is evidence that such exposure may cause cognitive impairment. This is why there has been a worldwide move to ban smoking in public places and there is a move on at the moment to make smoking around children against the law (not yet come into practice). Parents who smoke in the car with the ‘window cracked open’ think that this is o.k. but the smoke (and its toxic mixture) still gets into the car and into the confined area (eg back seats) where their children might be sat. Just throwing a few thoughts based on the accumulating evidence your way.

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Thanks, Dr. Heffernan. So summing up, nicotine on its own may be beneficial to memory (more research to come). Cigarettes contain nicotine plus a number of chemicals that poison mind and body.