Siegel states, "That suggests that smoking is associated with other types of health behaviors that are affecting the outcome. When other health behaviors were included, it completely wiped out the effect of smoking." [HHS] Spiegel also saw that the researchers’ results found that former-smokers performed better on the memory tests than smokers. He stated, "The reason their memory is better is not because they smoked -- that's not plausible.” [HHS]

He argues that former smokers or non-smokers may just have better overall health habits than smokers; may be better educated; or have naturally better cognitive levels.

As reported by the article from the HHS, Dr. Norman H. Edelman, a scientific consultant to the American Lung Association, summarizes: "This study is generally a confirmation of previous work. But there is a fundamental question: Are they stupid because they smoke or do they smoke because they are stupid?It is being reported that at least one scientist is not convinced of this connection between smoking and memory loss.

Michael Siegel, a professor of social and behavioral sciences at Boston University (Massachusetts, U.S.A.), states, "There are two things that are a little concerning about the [study] results that would give us pause before definitely concluding that smoking leads to a decrease in memory.” [U.S. Department of Health and Human Services (HHS): “Smoking Tied to Memory Loss in Middle Age”]