Tuesday, August 26, 2008

Imaging Study Suggests Nothing, Study Finds

This article is from the website ScienceDaily (Accessed 8/26/08).

I have multiple problems with this article. The findings contradict the title and the conclusions reached don't logically flow.

The title says "Alzheimer's Drug May Help Mild Memory Loss, Imaging Study Suggests." At least the author used the word "suggests." I don't know how many times I have read imaging research that implied causation rather than correlation (basic stats 101). If the study involves imaging (PET, fMRI, etc.) to study behaviors, thoughts, or emotions and the activity in the brain, that's not cause and effect. Another problem with imaging studies is external validity, the ability to generalize results to the whole population. This is because most studies have very few subjects, which is usually due to the expensive and time consuming nature of these studies. But I digress.

The article starts "Alzheimer's disease is the end result of gradual, progressive brain aging." Actually, Alzheimer's disease is the gradual, progressive, degeneration of the brain, but I digress again; however, what article about memory would be complete without the obligatory mention of Alzheimer's disease. This makes the study sound really, really important, "A small sample of adults with mild age-related memory loss was randomly assigned a daily placebo or Aricept (notice how the brand, not generic name is used), a drug that treats Alzheimer's symptoms (free advert anyone?)."

The condition being examined here is age-related memory impairment (AAMI). Normal elderly have have AAMI when they perceive age-related changes as dysfunctional. In standardized neuropsychological testing, scores are only poor when compared to the young (which one would expect with many comparisons between young and old). AAMI is usually nonprogressive.

"Both groups underwent PET brain scans before and after 18 months of treatment. The brains of people given Aricept showed an increased rate of metabolism and looked more normal than the brains of those who took the placebo." First, people with AAMI are normal, so technically, those given Aricept become abnormal. Secondly, I guess this result means that these people would show an improvement on memory tests, "Both groups scored the same on memory tests." Wait, I'm confused. So that would mean..."that PET scans may be more sensitive than neuropsychological tests in detecting drugs' effects." Go ahead, read that again. I'll wait.

So with no objective finding of an actual improvement in memory (because they're normal), the increased glucose metabolism (what is measured by PET) means that Aricept (I said the brand name twice now) improves memory. Makes sense, doesn't it?

Is it possible to squeeze any more conclusions out of this study? "The research suggests that the treatment of early symptoms of memory loss may protect the brain and help people with mild age-related memory impairment (what did I say about inferring causation?). The finding also shows how PET offers researchers a tool for tracking the effectiveness of drugs prescribed to treat age-related cognitive decline" (emphasis added). Not only does Aricept (three times) help people, but Aricept (where's my money Pfizer?) may also protect the brain. Additionally, PET scans allow researchers to track the effectiveness of drugs like Aricept (seriously, where's my money?).

The article ends with "Small (the researcher) is a consultant to Pfizer and Eisai, which manufacture and market Aricept (I bet he got money from Pfizer); and to Siemens, which manufactures and markets PET brain scanners (now I'm jealous)." I think a more accurate conclusion drawn from this study would be that people with AAMI given donepezil (take that Pfizer!) for 18 months is associated (i.e., is correlated) with increased brain glucose metabolism. Changes in memory were not detected.

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