October 19, 2005
Smoking Accelerates Cognitive Decline

If the threat of cancer, stroke, heart disease, and other old age diseases aren't enough to scare smokers into quitting how about the threat of becoming dumber as the toxins in cigarette smoke damage the brain?

ANN ARBOR, MI Smokers often say that smoking a cigarette helps them concentrate and feel more alert. But years of tobacco use may have the opposite effect, dimming the speed and accuracy of a person's thinking ability and bringing down their IQ, according to a new study led by University of Michigan researchers.

The association between long-term smoking and diminished mental proficiency in 172 alcoholic and non-alcoholic men was a surprising finding from a study that set out to examine alcoholism's long-term effect on the brain and thinking skills.

While the researchers confirmed previous findings that alcoholism is associated with thinking problems and lower IQ, their analysis also revealed that long-term smoking is too. The effect on memory, problem-solving and IQ was most pronounced among those who had smoked for years. Among the alcoholic men, smoking was associated with diminished thinking ability even after alcohol and drug use were accounted for.

The findings are the first to suggest a direct relationship between smoking and neurocognitive function among men with alcoholism. And, the results suggest that smoking is associated with diminished thinking ability even among men without alcohol problems.

Avoid neurotoxins. Your brain is your most valuable asset.

Those who think they will live long enough to enjoy the benefits of rejuvenation therapies ought to keep in mind that the brain is going to be the organ that is hardest to rejuvenate. The development of technologies for the growth of replacement organs will allow lots of old parts to get replaced with young parts. But you obviously can not replace your brain without replacing your identity with a different identity. Technologies for brain rejuvenation will come more slowly. Even stem cells therapies that replace dead neurons are far less than ideal because those dead neurons will be taking with them memories and personality elements. Take good care of your brain. Avoid toxins and avoid sports that might give you a concussion. You need for it to last a long time.

Share |      Randall Parker, 2005 October 19 09:58 AM  Aging Studies

James Bowery said at October 19, 2005 10:49 AM:

It would be interesting to get list of causes of neuron death quantified by degree of threat given typical lifestyles. For example, it is well known that ischemia causes neuron death and it has many secondary causes to varying degrees. Carbon monoxide is another cause of neuron death, which could explain the problems with smoking but could also guide risk behaviors involving one's environment.

For each of these causes there are counteracting phenomena such as activities that increase perfusion or that increase blood oxygenation, etc.

Hugh Angell said at October 19, 2005 4:24 PM:

I have heard of other studies which have indicated that tobacco users are less prone to
develop Alzheimers. No, not because they do not live long enough to develop it but because
the 'plaque' associated with Alzheimers patients does not develop in tobacco users to the
same extent.

I suggested my father smoke a couple of cigarettes per day when I learned of this. As to
statistical studies of smokers vs. non smokers you get what you get. Smokers are more
likely to come from cohorts where other factors are present.OTOH blacks and hispanics are
less likely to use tobacco than whites so... where does that leave one's assumptions about
long term cognitive ability?

michael reynolds said at October 19, 2005 4:56 PM:

Me am wondering whether applies to cigars, yes? Anyone my keys have seen? Mommy? Daisy. . . Daisy. . .

Mike Collins said at October 19, 2005 7:21 PM:

I'm wondering about my addiction of choice-CAFINE!!! Short term it seems to have some similarly helpful properties but long term hmmmm

dope fiend said at October 19, 2005 9:11 PM:

I have never heard of caffeine causing cognitive impairment. The biggest problem I see with heavy caffeine use is in its disruption of sleep. In contrast, amphetamines and dissociatives (i.e. PCP, ketamine, and DXM) are well known to cause cognitive problems, at least when used heavily. Methylphenidate (Ritalin), a substitued amphetamine, may also raise cancer risk, and all the above drugs target the same or similar receptors (PCP2, sigma1) as Ritalin and may raise cancer risk (if indeed Ritalin does). I have read that sigma1 receptor agonists suppress the immune system; I would imagine that immunosuprression would raise cancer risk.

michael vassar said at October 20, 2005 8:55 AM:

Like essentially all studies saying that such and such causes cognitive gain or decline, this study lacks any indication of the magnitude of the finding. Frustrating. I don't smoke, but you can show that anything is bad or good "with statistical significance" if you just select the right studies.

Chuckles said at October 26, 2005 7:36 PM:

Randall Parker,

Aside from cigarettes, what are other neurotoxins that I should avoid?


Randall Parker said at October 26, 2005 7:49 PM:


Neurotoxins to avoid? The list is long. Some notable ones:

- Most recreational drugs. Cocaine, amphetamines, etc cause brain damage.

- Mercury. That's a biggie. Avoid high mercury types of fish. See some links about mercury in a variety of types of fish in about the middle of that previous post of mine.

Chuckles said at October 26, 2005 8:57 PM:


Thanks for the pointers. The fish table is especially good.

As for recreational drugs, what about marijuana and opioids? Are they neurotoxins?

Thanks again.


remo williams said at October 27, 2005 9:19 AM:

From what Ive read about some Stanford stem cell experiments, the brain doesnt look so difficult to rejuvinate at a basic level. And repair from drug use should be the easiest to at least partially repair. Just toss in some more cells and let them go to work.

remo williams said at October 27, 2005 9:20 AM:

From what Ive read about some Stanford stem cell experiments, the brain doesnt look so difficult to rejuvinate at a basic level. And repair from drug use should be the easiest to at least partially repair. Just toss in some more cells and let them go to work.

Randall Parker said at October 27, 2005 9:45 AM:


Think of marijuana as having two parts. There are the psychoactive substances such as THC. But also, there's the smoke. It has many of the toxins that cigarette smoke has. So my guess is that it does some damage.

Opioids: Yes, they do damage when used long term. Not sure about short periods of usage.

You can google up results of brain scan studies where research groups have identified specific locations in the brain that suffer damage from specific recreational drugs. I'm too busy do to the searching right now. But I've done it before and was surprised by just how well the damage from specific drugs has been pinned down to particular parts of the brain. Some of the reports I came across were from UCLA.

It is pretty easy to dig up the info. Take, for example, a google search on brain damage mri cocaine. Change that to use fmri as a variation. Also use other drugs in place of cocaine and see what you find.

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