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A cognitively active lifestyle that involves reading and processing information in old age may delay the onset of dementia in Alzheimer's disease by as much as 5 years, a longitudinal study suggested.

Older adults who had the highest level of late-life cognitive activity had a mean onset age of Alzheimer's dementia of 94, reported Robert Wilson, PhD, of Rush University Medical Center in Chicago, and colleagues.

In contrast, those with the lowest late-life cognitive activity levels developed dementia at age 89, they wrote in .

"Our study shows that people who engage in more cognitively stimulating activities may be delaying the age at which they develop dementia," Wilson said in a statement.

"It is important to note, after we accounted for late-life level of cognitive activity, neither education nor early-life cognitive activity were associated with the age at which a person developed Alzheimer's dementia," he continued. "Our research suggests that the link between cognitive activity and the age at which a person developed dementia is mainly driven by the activities you do later in life."

"This study provides further support for the concept of cognitive reserve, where genetic and life exposures allow some people to cope better than others with age- or disease-related brain changes," noted Yaakov Stern, PhD, of Columbia University in New York City, who wasn't involved with the research.

"Previous work has suggested many exposures that can contribute to cognitive reserve, including education, aspects of occupational attainment, and late-life leisure activities, along with IQ," Stern told 番茄社区.

"What is interesting here is that this paper suggests that late-life cognitive activity can contribute to this reserve," he added. "Further, their autopsy data indicates that the late-life cognitive activity does not influence the pathology itself, making it more likely that it influences cognitive reserve -- the ability to cope with the pathology."

The study involved 1,903 older adults from the longitudinal who were dementia-free at enrollment. Participants had annual clinical evaluations to diagnose dementia and Alzheimer's disease. Those who died had a neuropathologic examination.

Mean age at baseline was 79.7. Participants had completed an average of 15 years of formal education; most were women (74.9%) and white (89.1%). They had a median of one of seven chronic medical conditions such as cancer or heart disease, and a median income between $35,000 and $49,999.

At baseline, participants reported how frequently they participated in seven specific cognitively stimulating activities on a 5-point scale. The activities emphasized seeking or processing information: daily reading, or time spent each year visiting a library, reading newspapers, reading magazines, reading books, writing letters, or playing games like puzzles, cards, and board games. Scores ranged from 1 (no time) to 5 (every day or almost every day).

People in the 90th percentile of cognitive activity scored an average of 4.0, indicating they were involved with these activities several times per week. Those with the lowest cognitive activity -- the 10th percentile -- had an average score of 2.1, indicating activities several times per year.

Over a mean of 6.8 years of annual followup evaluations, 457 people were diagnosed with incident Alzheimer's dementia at a mean age of 88.6 (range 64.1-106.5). In an extended accelerated failure time model, a higher level of baseline cognitive activity (mean 3.2) was associated with older age at Alzheimer's dementia onset (estimate 0.026, 95% CI 0.013-0.039).

An activity score of 2.1 (10th percentile) was linked with an average dementia onset age of 88.6. A activity score of 4.0 (90th percentile) was associated with an average onset age of 93.6. Cognitive activity continued to be related to age of Alzheimer's dementia onset after adjusting for sex, education, APOE4 status, and baseline social activity and loneliness. The association persisted even when people who had mild cognitive impairment at baseline were excluded.

In the 695 participants who died and had a neuropathologic examination, cognitive activity was unrelated to postmortem markers of Alzheimer's and other dementias, including amyloid burden and tau.

Overall, the bases of observed associations between cognitive activity and age of Alzheimer's dementia onset are uncertain, Wilson and colleagues noted.

"One possibility is that low cognitive activity is an early sign of Alzheimer's disease (reverse causality hypothesis)," they wrote. "In the present analyses, however, postmortem markers of Alzheimer's disease and other dementias were unrelated to the self-report measure of cognitive activity, consistent with prior research in this cohort."

"We think a more likely possibility is that cognitive activities lead to changes in brain structure and function that enhance cognitive reserve," the researchers added.

The main limitation of the study is that analyses are based on a selected group of mainly white, well-educated participants. "Further research will be needed to establish whether the findings will generalize to more diverse cohorts with a wider range of age and cognitive experiences," they wrote.

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