Robert S. Wilson and his colleagues at Rush Presbyterian-St. Luke's Medical Center in Chicago found their subjects in the ongoing Religious Orders Study. Upon entry into the study, 801 elderly priests and nuns, none with AD, had been queried about time spent in seven common activities that involve information processing as a central component (viewing television; listening to radio; reading newspapers; reading magazines; reading books; playing games such as cards, checkers, crosswords or other puzzles; and going to museums.) Based on frequency of participation in each activity, a composite activity score on a five-point scale was determined for each subject.

After controlling for age, sex, and education, the researchers found that a one-point increase in the cognitive activity score was associated with a 33 percent reduction in risk of AD. Additional analyses attempting to control for baseline levels of cognitive decline found that a one-point increase in the cognitive activity score was associated with reduced decline in global cognition (by 47 percent), working memory (by 60 percent), and perceptual speed (by 30 percent).-Hakon Heimer.

Reference:
Wilson RS et al. Participation in cognitively stimulating activities and risk of incident Alzheimer's disease. JAMA 2002 Feb 13;287(6):742-8. Abstract