Stephen: Thanks for your analysis of the B vitamins and Alzheimer's study as reported.
Query re cognitive impairment: Is it possible that previous studies showing some correlation between brain atrophy and the likelihood of developing Alzheimer's is relevant to the claims? http://brain.oxfordjournals.org/content/132/8/2026.short http://radiology.rsna.org/content/229/3/691.full Allen Esterson Former lecturer, Science Department Southwark College, London allenester...@compuserve.com http://www.esterson.org ----------------------------------------------------------------------- [tips] B vitamins, Alzheimer's, and telling the whole story sblack Thu, 09 Sep 2010 22:46:47 -0700 Our CTV television network, which prides itself in presenting the very latest in medical advances, adequate evidence or not, had another one tonight. A randomized controlled study which showed that a 2-year regimen of B vitamins in the elderly with mild cognitive impairment slows the rate of MRI-assessed brain atrophy. But funny, I said to my wife, there's no mention of cognitive improvement. Surely in a clinical study of this size and sophistication, not to mention expense, they would measure cognition before and after treatment. And if they did, wouldn't they be bound to mention the outcome? Think again. The study turns out to be Smith et al (2010). They took a battery of cognitive measures, all right, but there was nothing in the methods I could see noting that they took these measures after treatment as well as before. But apparently they did. Buried in a section labeled "secondary outcomes" was this statement "Although the study was not powered to detect an effect of treatment on cognition (findings to be reported separately), in a post hoc analysis we noted that final cognitive test scores were correlated to rate of atrophy". My translation: We didn't find any difference between placebo and vitamin treatments in cognition, so we did what we could to put a positive spin on this, and also to forget about it. Anyway, if we had more subjects, we might have seen something (the "not powered" excuse). They provide a brief similar excuse ("not powered to detect effects of treatment on cognitive test scores") in a later section titled "Possible therapeutic implications". No data, of course. But curiously, if one goes to where they registered their trial before it began, they specified that in their study a "primary outcome measure" was "Changes in performance on a variety of cognitive tests". Nothing there about "not powered". See: http://www.controlled-trials.com/ISRCTN94410159/94410159 So it seems that in their haste to get out the good news (vitamins slow brain atrophy, which is indeed impressive), they somehow avoided providing the bad news (no detectable effect on cognition). Perhaps providing it would tend to dampen sales for the products for which Dr. Smith is listed as inventor with patents held by the University of Oxford and on which he "could benefit financially" (see "competing interests"). Stephen Smith, A. et al (2010). Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled tria. PLoS ONE, September 2010, v. 5, issue 9, e1244 Available here: http://tinyurl.com/Bvitamins-for-the-brain -------------------------------------------- Stephen L. Black, Ph.D. Professor of Psychology, Emeritus Bishop's University e-mail: sblack at ubishops.ca 2600 College St. Sherbrooke QC J1M 1Z7 Canada --- You are currently subscribed to tips as: arch...@jab.org. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=4702 or send a blank email to leave-4702-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
