Smoking 'won't prevent Alzheimer's'

The tobacco industry worked for two decades to skew research into smoking and Alzheimer's disease, to promote the wrong belief it could prevent the degenerative condition, a review of research has found.

US-based scientists have reviewed more than 40 research papers published since 1984, to highlight those with industry links which also suggested smoking could be good for the brain.

A quarter of the papers were found to have industry influence - either through direct funding or using researchers who were also consultants to the industry or who had other ties.

In many cases these relationships were not disclosed, according to the analysis, which found industry-linked papers dotted through the scientific literature up to 2003.

Professor Jurgen Gotz, from the University of Sydney's Brain & Mind Research Institute, welcomed the review, saying it should help to set the record straight on nicotine's effect on the brain.

"There have been many studies looking at the incidence of Alzheimer's disease in general, and dementia in general, and the role of nicotine," Prof Gotz said.

"Some of these studies showed, or claimed to show, that smoking, in a sense, protects from Alzheimer's disease.

"It turns out when one takes these (industry-linked) studies into consideration ... the bottom line is smoking indeed is associated with an increased risk of Alzheimer's disease."

The review, by scientists at the University of California, found the industry-linked papers tended to suggest smoking was either not a risk factor or that it protected against Alzheimer's disease.

The independent studies - which outnumbered the industry-linked studies - showed how smoking posed nearly double the risk of developing the disease.

Studies into tobacco and Alzheimer's got underway in the late 1970s in response to anecdotal reports of lower rates of the condition among older smokers.

The beneficial claim continues to circulate via the internet and occasionally it pops up in the mainstream press - including in a 2008 article published in the US' top selling Oprah Magazine.

Prof Gotz said it was time to end the myth that smoking could be good for the brain.

"This has been disproved both in humans, as studies show, and in animals and cell culture systems," Prof Gotz said.

"Nicotine ... increases the degenerative changes in the brain."