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NEW YORK (Reuters Health) - While staying mentally active in old age has been linked to a delayed onset of dementia, seniors who engage in such brain "exercise" may actually have a faster rate of decline once Alzheimer's is diagnosed, researchers reported Wednesday.
The findings, published online in the journal Neurology, do not mean that a mentally stimulating lifestyle is a bad thing.
Instead, the researchers suspect that their findings may point to the "cost" of delaying Alzheimer's onset by keeping the mind active with hobbies, reading, crossword puzzles and the like.
That is, once these mentally active older adults are showing the signs of dementia and are ultimately diagnosed, they may have a more advanced stage of brain damage compared with less mentally active seniors.
This idea fits in with the "cognitive reserve" hypothesis of dementia. That theory basically holds that people who are mentally active can better withstand the gradual brain-cell damage that marks Alzheimer's disease and other forms of dementia. But once that damage reaches a certain threshold, dementia symptoms will become apparent.
So mentally active older adults may develop dementia later than those who "exercise" their brains less often. But once they do develop it, they are in a more extensive state of brain damage.
That, at least, is "the working hypothesis," said Dr. Charles B. Hall, a researcher at Albert Einstein College of Medicine in New York. Hall was not involved in the current study, but is researching the connection between cognitive activities and dementia.
In an interview, he said these latest findings confirm work by his research group and others finding a link between a mentally active lifestyle and a delayed onset of dementia, but also a faster decline once dementia is diagnosed.
The current study, led by Dr. Robert S. Wilson of Rush University in Chicago, included 1,157 older adults who were dementia-free at the outset and were evaluated for cognitive decline over roughly six years.
At the study's start, participants reported on how often they engaged in a number of activities that were considered mentally stimulating -- including reading, doing crosswords or other puzzles, playing games like cards or checkers, watching TV, listening to the radio and going to museums.
During the study period, 614 participants remained cognitively healthy, while 395 developed mild impairment in their thinking abilities, and 148 were diagnosed with Alzheimer's disease.
Wilson's team found that among the group who remained healthy, those who reported a greater number of cognitive activities showed a slower rate of decline in cognitive tests over six years. Test scores remained essentially unchanged among those in the top 10 percent for cognitive activities, but showed a gradual dip among those in the bottom 10 percent.
In contrast, among study participants who were diagnosed with Alzheimer's, those who were the most mentally active at the study's outset showed a quicker rate of decline over time than those who had been the least mentally engaged.
According to Wilson's team, all of this suggests that mentally stimulating activities in older age might "compress" the amount of time a person ultimately spends with dementia symptoms.
However, Hall pointed out that the key limitation of this and past studies on the issue is that they are observational studies. That is, they can show an association between mental activities and dementia onset and progression, but cannot prove cause-and-effect.
"The evidence from observational studies suggests that cognitive activities might delay the onset of dementia," Hall said, "but that has to be confirmed in intervention studies."
In an intervention-type study, participants would, for example, be randomly assigned to regularly perform some sort of mentally stimulating activity and then have their cognitive health followed over time and compared with that of a similar group who did not perform the activity.
If staying mentally active does delay dementia onset, evidence so far suggests the benefit would be modest.
In a study Hall and his colleagues published last year, they found that of older adults who developed dementia during the study period, the most mentally active ones were typically diagnosed just over a year later than the least mentally active men and women.
People in the most active group typically reported 11 "activity days" per week -- meaning, for example, they performed one activity, such as reading, writing or playing games, on all days of the week, and a second activity on four days of the week. The least active group reported four activity days per week.
"This doesn't prevent dementia. This doesn't prevent the (brain) pathology," Hall said. However, he added, if mental activities were found to delay dementia symptoms, or the need for nursing home care, by even a year, that would have a "tremendous public health impact."
"I'm not ready to tell everyone to do crossword puzzles," Hall said. On the other hand, he added, there would be little chance of harm in doing so.
SOURCE: link.reuters.com/bar78n Neurology, online September 1, 2010.