Engaging in mentally stimulating activities may slow the decline of cognitive skills but eventually increases the rate of cognitive decline in persons who go on to develop dementia, according to new research. However, this pattern means that a person could spend less time in a state of dementia.

This finding emerged from a study of Chicago residents, aged 65 years and older. The participants, who were dementia-free at baseline, underwent a detailed clinical evaluation and were interviewed again every three years for an average of 11.3 years. They rated how frequently they took part in seven activities that centered on information processing, such as watching television, listening to the radio, reading newspapers, playing cards, and going to museums. The more often a person engaged in mentally stimulating exercises, the higher his or her score on a five-point cognitive activity scale.

At the time of the current analysis, 614 subjects still had no cognitive impairment, 395 had mild cognitive impairment (MCI), and 148 had developed Alzheimer’s disease (AD).

Among those without cognitive impairment, the annual rate of global cognitive decline was reduced by 52% for each additional point on the cognitive activity scale. In the MCI group, cognitive decline rate was unrelated to cognitive activity. In the AD group, the mean rate of decline per year increased by 42% for each point on the cognitive activity scale.

“More frequent cognitive activity was related to slower cognitive decline in those without cognitive impairment and more rapid cognitive decline in AD, with no effect on MCI,” the investigators explained (Neurology. 2010;75:990-996). “The results suggest that late-life cognitive activity compresses the cognitive morbidity of AD by delaying its onset and by hastening cognitive decline after dementia onset.”

The results suggest that cognitive enrichment interventions may need to be initiated before cognitive impairment develops, “possibly because many persons with MCI already have substantial levels of AD pathology.”