Sunday, August 12, 2012

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.  

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.
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. 


  1. Stearic acid is not a carcinogen, so I'm at a loss to understand why he included it in his list. There's a chart in this PDF that lists the foods that contain high amounts of it:

    What he might also have mentioned is that tobacco is a mild MAO-A inhibitor. I'm thinking that would have some interesting brain effects over time.

    I'm a smoker who is currently quitting. Nicotine patches and lozenges are the mainstay of my existence, even though I no longer have strong cravings for cigarettes. If I forget the patch (which I've been known to do), the brain effects are obvious and troubling.

    I've collected a few nicotine-related articles over the years. If I can find them, I'll send them along.

  2. Hey there, Rhonda, nice to connect with you again although I like talking with you on the HER-2 board as well. I know that you know your stuff!

    About stearic acid, that is weird. I'll alert Dr. Heffernan about your post and perhaps he'll respond. Also, don't know much about MAO-A inhibitors, so perhaps he'll comment about that too.

    You mentioned that if you forget your nicotine patches, then your brain effects are troubling. What do you mean?

    So glad that you're quitting smoking though. Congrats on that!

    All the best.


  3. In relation to the recent article on 'second-hand smoke and memory loss. The list of chemicals provided included typical chemicals found in cigarette smoke (that are akin to those found in household items) and some of the potentially carcinogenic chemicals found in cigarette smoke. Perhaps this would have been made clearer if the list had been divided between these categories for clarification on a) the typical types of chemicals found in cigarette smoke, b) the types that are believed to be carcinogenic. This does not detract from the growing body of evidence that health and cognition are compromised by exposure to second-hand smoke.
    Tom Heffernan

  4. Thanks for clarifying that, Dr. Heffernan.

    As for me, Idelle, after thinking I'd managed my cognitive deficits with supplements--I experienced improved recall, possibly even better than pre-chemo--I decided it was time to quit smoking. I expected the first days to be difficult, so I didn't pay much attention to my inattention, and by the time I "graduated" to the 14 mg patch, I felt pretty good.

    Then I went to 7 mg, and I even skipped the patch entirely on occasion (i.e., when I forgot to apply it). It was on one of those "no patch" days that I cleaned the turtle tank and caused it to overflow and flood the house. Shortly thereafter, I had a lapse, and although smoking made me feel pretty sick, it also made me realize I wasn't operating on all cylinders.

    After a bit of experimentation, it is apparent that the 14 mg patch is the right dose. It doesn't bring me up to full speed, but it's a whole lot better that a lower dose or doing without. At least with 14 mgs nicotine, I have the occasional illusion of clarity, but without it, I'm walking around on autopilot, pretty much unable to string words together or hold onto a single thought from one room to the next. It seems to have nothing to do with recall--for example, I can still find things I've put in odd places if I concentrate for a moment--but everything to do with my ability to implement my thoughts.

    The only problem with the patch is that I still sometimes forget to put it on (bumbling around until I figure out why I'm bumbling around) or take it off (at night, which means my sleep is disturbed by vivid dreams). I'm hoping to be a bit more even as soon as I nail the routine.