For the intellectually active, Alzheimer’s diagnosis begins a steep slide

The vaunted protection that intellectually active adults get from Alzheimer’s disease has a dark downside, a study released Wednesday has found. Once dementia symptoms become evident and Alzheimer’s disease is diagnosed in such patients, their mental decline can come with frightening speed.

That finding, published in the journal Neurology, comes from a study of 1,157 Chicago-based seniors who were followed for an average of just over 11 years. Six years after gauging the extent to which the study participants engaged in activities that challenged their mental capacities, researchers from Rush University Medical Center Alzheimer’s Disease Center made periodic assessments of the study participants’ cognitive health and traced the trajectories of their brain health.

All told, 148 of the participants were diagnosed with Alzheimer’s disease during the follow-up period, and 395 were found to have mild cognitive impairment—intellectual problems that are less severe than Alzheimer’s disease, but which often precede such a diagnosis.

While all participants’ mental function showed yearly declines, the steepest downward trajectories belonged to those who had been diagnosed with Alzheimer’s disease, but who had reported high levels of mental engagement at the outset of the study. Fellow Alzheimer’s sufferers who had not sought out much intellectual stimulation at the study’s outset showed a more gradual decline in their function.

“In effect, the results of this study suggest that the benefit of delaying the initial appearance of cognitive impairment [in Alzheimer’s disease] comes at the cost of more rapid dementia progression,” the author wrote.

The findings support a common observation of those who treat intellectually minded patients who go on to be diagnosed with Alzheimer’s disease—that once diagnosed, their decline is rapid. It also underscores a growing body of evidence that the bright and mentally-active may not beat Alzheimer’s disease, but can hold off its ravages for months or years longer than those who are not so engaged.

Dr. John M. Ringman, a UCLA neurologist and assistant director of the Mary S. Easton Center for Alzheimer’s Disease Research, said he sees regular evidence of the phenomenonen in his clinical work, as well as in brain-imaging scans that can detect the physical signs of Alzheimer’s disease while a patient is still alive: Patients with a history of intensive mental engagement seem to develop a “cognitive reserve,” said Dr. Ringman. That mental strength frequently allows them to function almost normally, he said, even as the amyloid plaques and neurofibrillary tangles that are the hallmarks of the disease have advanced upon the brain.

By the time such a patient comes to his office complaining that his memory and mental function are not what they used to be, the disease has progressed significantly, said Ringman. The decline from that point can be precipitous.

In a disease that evidence now suggests takes years, perhaps decades, to show up in everyday behavior, Ringman said “it’s hard to quantify this cognitive reserve.” The strength of the study published Wednesday is that it gathered copious evidence of participants’ mental status and activity at the outset and followed them for more than a decade, he added.

--Melissa Healy/Los Angeles Times