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CAN A LITTLE PHYSICAL ACTIVITY
REALLY PREVENT ALZHEIMER’S? (October 2002) The news headlines trumpeted the possibility based on an article published in the journal Neurology, December 21, 2001. Three relevant quotes from the article seem somewhat contradictory. 1. The goal of the study is "to determine whether leisure activities modify the risk for incident [new cases of] dementia". 2. "the data suggest that engagement in leisure time activities may reduce the risk of incident dementia possibly by providing a reserve that delays the onset of clinical manifestations of the disease". 3. "possibilities that interventions that enhance life experience and activities might reduce the risk of developing dementia". The authors cannot seem to decide whether the leisure time activities prevent Alzheimer’s or just delay its appearance. They studied 1,772 persons over age 65, following them for an average of 2.9 years (range up to 7 years), during which time, 209 developed dementia. Of these, 153 had probable or possible Alzheimer’s; the others were demented for other reasons (such as reduced blood supply to the brain). Those doing more of thirteen leisure time activities were, depending on the statistical technique used, 12 to 38 percent less likely to develop dementia. The thirteen "activities" included: knitting, walking, being visited by relatives, physical conditioning, going to movies or restaurants, reading, doing volunteer community work, playing cards or bingo, going to a club or center, going to classes, going to church. Commentary: It would be nice if some leisure time activities did prevent or delay Alzheimer’s, but there are a great many problems with this report aside from the fact that a 12 to 38 percent reduction is not all that great in this kind of study. - The followup period is so short that the greater apparent risk for those people with the least activities may be the result of early Alzheimer’s. They should have excluded all dementia occurring within two years of the start of the study, or at least done separate analyses for those developing dementia within two years of the initiation of the study and for those developing the disease later than that. Unfortunately, it appears the followup period was under three years for most of the group studied. - the title says Alzheimer’s, but one-quarter of those they studied apparently did not have Alzheimer’s and others were listed as ‘possible" Alzheimer’s. Part of the analysis should have been restricted to those with probable or proved Alzheimer’s. - there is no analysis of the intensity or frequency of the activities. Does walking mean one block or one mile? Daily? Weekly? Monthly? - the scoring system (one point for each activity) is pretty simplistic and could introduce all sorts of biases.
This is a good group conducting the study and the issue is potentially important, but we need a much better study to draw even preliminary conclusions. Besides, two other studies are essentially negative. Alzheimer’s is a terrible disease. As the society ages, the toll from this disease will increase. Unfortunately, a major reduction in the occurrence of this disease is unlikely to result from more physical activities. Scarmeas, N., et al. Influence of leisure activity on the incidence of Alzheimer’s disease. Neurology. Vol 57 (December 21) Pgs 2236-2242. 2001.
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