From the article:
"A new Washington University study shows the part of the brain used to daydream is the same where Alzheimer's disease develops -- in some people -- later in life."
This study has not found that daydreaming causes alzheimer's disease. In fact, a lot of daydreaming might prevent alzheimer's disease.
Users of paraliminals and hypnosis tapes might worry if they draw unsupported conclusions, because it's often advised in hypnosis to "just let your mind wander."
It seems paradoxical and untrue that using a part of one's brain often and well would lead to it necessarily becoming diseased.
Related to alzheimer's disease: I remember reading that studies have shown that engaging in complex activities with your digits (fingers) throughout your life is related to a lack of alzheimer's disease later on. Activities such as playing the piano or playing video games often might help to keep you sharp.
We have to be careful about drawing conclusions willy-nilly from the results of studies.
Also from the article:
"The National Institute on Aging, which funded the study, said the data are interesting even if the conclusion is speculative."