An analysis of existing studies on smoking and Alzheimer's disease (AD) found an interesting discrepancy: studies performed by those with affiliations to the tobacco industry suggested smoking protects against AD, while studies by those without tobacco industry affiliations found that smokers had nearly double the risk for AD.
The Study
Researchers at the University of California at San Francisco reviewed 43 studies published between 1984 and 2007. Using previously secret tobacco industry documents, the researchers determined whether authors of the previous studies had an affiliation with the industry--about one-fourth of the studies were found to have an industry affiliation.
Taken as a whole, the 43 studies found a statistically insignificant risk factor for developing AD from smoking. However, the picture changed when the UCSF team considered the studies separately. Studies without tobacco industry affiliations found a risk factor of 1.72, indicating that smoking nearly doubles the risk for AD. Studies with tobacco industry affiliations found a risk factor of .86--which actually suggests that smoking lowers a person's risk for AD.
What Does This Mean?
This new look at existing research casts casts serious doubt on the myth that smoking can protect against AD. Smoking is known to have a number of serious health consequences, and it looks as though an increased risk for Alzheimer's disease may be among them. This study is also a sobering look at the conclusions reached by industry-sponsored research, reminding us to be careful where we get our information.
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