As people grow older, memory and thinking skills decline relatively rapidly in those who end up with later dementia compared with folks who are aging normally—even before dementia or Alzheimer's disease is officially diagnosed. That's according to a study published today in the journal Neurology. As part of a longitudinal aging study of older black and white individuals living in a Chicago community, researchers at Rush University Medical Center in Chicago tested participants' memory and thinking skills every three years for up to 11 years. (The subjects' average age at the beginning of the study was 79.) The findings suggested that the memory and thinking abilities of subjects who had mild cognitive impairment, the precursor to Alzheimer's disease, declined two times as fast every year as the abilities of those without any cognitive problems at the beginning of the study. Likewise, thinking ability and memory in subjects with Alzheimer's disease declined four times as fast as in those without any cognitive problems. No significant differences were found between white and black participants.
These results, says Robert Wilson, the lead study author and senior neuropsychologist at the Rush Alzheimer's Disease Center, suggests that by the time of an actual diagnosis, Alzheimer's disease or another dementia is probably already in its final stages. The disease has likely been present for many years, though in a far less debilitating form. "There persists the idea that some decline in memory is typical" with age, but that may not be entirely accurate, he explains.
Identifying the rates of memory and other cognitive decline in various types of older individuals, says David Knopman, author of an accompanying editorial and a neurologist at the Mayo Clinic in Rochester, Minn., is very important to the study of Alzheimer's and its precursors. "People with mild cognitive impairment fortunately decline fairly slowly" over a matter of quite a few years, for example, "but once [a person] reaches dementia, cognitive impairment starts accelerating, and the care demands [on family caregivers] will change more quickly," he says. "In typical cases, the middle temporal lobe where short-term memory is mediated" is where cognitive decline begins, says Knopman. Once dementia occurs, other areas of the brain are affected.
So, should you fear for the status of your middle temporal lobe because you recently misplaced your keys, or went upstairs and couldn't remember why once you got there? Should the fact that your spouse or parent has similar issues be the cause for alarm? No, experts say. Those types of mental slips are better attributed to a lapse in attention or distraction, not actual cognitive decline, Wilson says. However, "if you're really experiencing memory loss, it's unlikely to be benign," he adds. It's extremely difficult for an individual or their loved ones to parse out true cognitive decline from less concerning mental lapses. And a heightened sense of alarm or paranoia only complicates one's perception.
Knopman says he sees a wide variety of patients in his practice, including the "worried well" who are concerned but have no cognitive deficits. "We all forget," he says. While people with genuine memory problems may be aware of the issue early on, with progression of the disease "they lose the capacity for insight, so they think everything is fine," he says. The vast majority of patients Knopman sees have been brought in by a concerned loved one.
Here are a few indicators that actual trouble may be brewing:
Difficulty with the sense of smell. That's right, the nose might offer a very early sign of cognitive change. Some of Wilson's previous research suggested the possibility of predicting who would develop mild cognitive impairment or Alzheimer's disease, even in those who showed no evidence of mild cognitive impairment, by measuring subjects' olfactory system—part of the brain's hippocampus, which is affected by Alzheimer's. Subjects had difficulty recognizing once familiar smells.