The study stated that smoking is already a known risk factor for stroke, which is a loss of blood flow that damages the brain. The research tested smokers, former smokers and never smokers on such things as shot-term memory, time and place orientation, attention and calculation. Within a two year time span, all three groups of persons aged 65 and over experienced a decline in cognitive abilities, but the study found that older smokers had a significantly greater decline. Former smokers had a slightly more rapid decline than never-smokers, but the difference was not significant. The study adjusted for other factors that might affect cognitive function, such as age, education and history of stroke, but did not take into account such things as alcohol consumption, how heavily people smoked, how long former smokers smoked and when they quit.
Researchers know that alcohol and diet are important factors in cognitive function.
Thus, more research is needed to see if Launer's findings will be confirmed by others. However, Launer's study raises one more concern about smoking. The study, by scientists from a number of Dutch universities, is one of the largest to investigate the link between smoking and Alzheimer's. The study of nearly 7,000 people aged over 55 found smoking was a strong risk factor for both men and women. The researchers found smoking to be a risk for dementia even when they adjusted their analysis for variables such as alcohol intake and educational levels.