nos-trum. pronunciation: \nos'-trum\. noun. Etymology: Latin, neuter of noster our, ours.
1. a medicine of secret composition recommended by its preparer but usually without scientific proof of its effectiveness.
2. a usually questionable remedy or scheme.
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Tuesday, October 19, 2010

B-12 And Alzheimer's Link: Almost Certainly A Meaningless Association

 
Just because something (drinking coffee, say) is associated with something else (less risk of Parkinson's disease) doesn't mean we need to do anything about it.

I was reading an article in BBC News Health (Oct 18) about a new study that links Vitamin B12 to Alzheimer's disease, one of the forms of dementia.  I didn't read the real study, just the news article.  Apparently, the study shows that people with the highest levels of B-12 are least likely to be diagnosed with dementia...at least, if you think looking at 271 people from Finland counts as a good study.

But this is what caught my attention:
"A recent trial found that "brain shrinkage", which has been associated with Alzheimer's, was slowed in older people taking high doses of vitamins, including B12."
And?

The implication is, if less brain shrinkage, then less Alzheimer's, so take B-12.

But we get fooled by this kind of thing all the time. 

It's typical that when we go further and study this association we find that taking B-12 does decrease the shrinking, but the Alzheimer's still occurs...you just have a less shrunken brain accompanying your dementia.

You can't take a complex physiologic environment with thousands of interacting variables and isolate a simple phenomenon of cause and effect.

The classic story for how we are fooled into thinking we're measuring something that really matters is the case of heart rhythm abnormalities (arrhythmias) after a heart attack (or myocardial infarction, MI).  Studies showed that people who have irregular heart beats after an MI were less likely to survive. 

Along came a new group of drugs to control heart rhythm, reducing the irregular beating.  So doctors charged in, giving the new drug to MI patients who showed a tendency to arrhythmias, and...behold...their hearts beat regularly.

But, after some years of experience with the drugs it was learned that these same folks who showed a tendency to irregular rhythms--but had their rhythms controlled by the drugs--were still more likely to die.  And in some cases the drugs themselves caused adverse reactions...occasionally, lethal ones.

There's an old adage in we get taught in medical school:  "Don't treat the test result, treat the patient."  We shouldn't have assumed that just because the finding was present (irregular heart rhythm) in those who were at increased risk of dying, that it was the important factor in raising that risk.  It wasn't; something else is.

Today's post is a cautionary tale about stories like the above on B-12.  We need to disregard pretty much all of them...they're almost always meaningless.

One last thought.  A study was done some years ago that showed lap dancers who weren't on birth control pills (i.e., they were fertile) got more tips.  The researchers concluded that men were more attracted to fertile women.

Given this discussion above of "associations" between things, does that conclusion make any sense to you?

Doc D
 

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