[Tezcatlipoca]

http://twitter.com/bengoldacre/status/23995503993

Originally Posted by BadScience's Doctor Ben Goldacre via Twitter

Vitamin B slows alzheimers if you delete a third of your patients: note AD Smith is a previous Holford collaborator http://dlvr.it/4y9sL

"Vitamin B and slowing the rate of Brain Atrophy: the numbers don’t add up"

Originally Posted by Carl Heneghan via the above link

A new study suggests high doses of B vitamins may halve the rate of brain shrinkage in older people experiencing some of the warning signs of Alzheimer's disease.’ reports the BBC

A total of 168 participants (85 in active treatment group; 83 receiving placebo) completed the MRI section of the trial from 271. Therefore the study lost a lot of participants – where did they go?

The researchers state the efficacy analyses were performed on the basis of the intention-to-treat principle. But I have serious concerns that they were not.

The intenton -to-treat aims to avoid bias arising due to drop outs. For example, if people who had worse cognitive decline tend to drop out at a higher rate, even a completely ineffective treatment may appear to be providing benefits.

Thus if you just compare the primary outcome measure before and after the treatment for only those who finish the study (forgetting to count those enrolled originally, but subsequently excluded or not followed up) the results are likely to be misleading.

Thus everyone who begins the treatment, in this case Vitamin B, should be considered to be part of the trial and have the outcome assessed.

(snip)