VANCOUVER, B.C. – Mild cognitive impairment warrants clinical attention as it confers a sharply elevated risk of death and also portends increasing social isolation, according to a pair of longitudinal studies.
Amnestic MCI Is Independent Risk Factor for Death
In the first study, investigators led by Mindy J. Katz, a senior associate in the neurology department of the Albert Einstein College of Medicine, New York, followed 733 community-dwelling participants aged 70 years or older from the Einstein Aging Study.
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Mindy J. Katz
Results showed that after confounders were taken into account, individuals with the amnestic type of mild cognitive impairment (MCI), which affects memory, were more than twice as likely to die in the next 5 years as were their cognitively intact counterparts. But those with nonamnestic MCI, which affects executive function, judgment, visuospatial ability, and/or language, were not at increased risk.
The heightened mortality with the former may be related both to its frequent progression to Alzheimer’s disease and to its impact on adherence to medical therapy for comorbidities such as hypertension and diabetes, according to Ms. Katz. "If they can’t remember to take their medications, if they don’t keep their appointments with their doctors, their medical care might not be as good as that of someone who is ... capable of keeping these appointments and taking their medications," she said in an interview at the Alzheimer’s Association International Conference 2012.
The findings apply only to people who meet diagnostic criteria for amnestic MCI, she stressed. "Just because you forget where you put your keys or you can’t remember why you walked into a room, that’s not a reason to panic." However, "after you’ve been clinically evaluated and the clinician feels that you really do have a true memory impairment, then it’s a warning sign for both the individual to prepare for the future and for caretakers to be aware that maybe this person might need more care or a plan for care in the future, and to make provisions both financially and in terms of caretaking that might be involved going forward for that individual."
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Dr. Richard Lipton
Senior author Dr. Richard B. Lipton, also of the Albert Einstein College of Medicine, noted that there has been some question as to whether MCI is an important entity. "Well, if it’s associated with an increased risk of death, then presumably it’s important, because death is the ultimate hard end point that is face-valid to all parties," he said.
Identifying MCI is now key for two reasons, according to Dr. Lipton. "Ultimately ... that will be a group that’s treated to keep them from progressing and developing full-blown Alzheimer’s disease. But even today, it’s important because adherence to medical therapy for people with memory impairment requires planning and family support."
In the study, 10% of participants had amnestic MCI and 9% had nonamnestic MCI at baseline. Additionally, 3% developed dementia at some time after their first evaluation.
During follow-up, nearly a third of study participants died. In a multivariate analysis, those with amnestic MCI had a significantly elevated risk of death relative to their cognitively intact peers (hazard ratio, 2.17). The other significant independent risk factors were dementia (3.26), advancing age (1.10), Geriatric Depression Scale score (1.09), and comorbidity index (1.34).
In contrast, nonamnestic MCI did not significantly affect risk, nor did educational attainment. APOE e4 allele status showed a trend toward increased mortality.
Withdrawal From Community Life
In the second study, a team led by Dr. Jeffrey Kaye of Oregon Health and Science University in Portland followed 140 community-dwelling, nondepressed older adults from the Intelligent Systems for Assessing Aging Change (ISAAC) cohort who had a mean age of 84 years at baseline.
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Dr. Jeffrey Kaye
The investigators used new technology called pervasive computing or embedded ambient sensing, outfitting the participants’ homes with motion sensors and with contact sensors on doors to detect 24/7 activity patterns, including travel outside the home.
At baseline, the 20% of participants who had MCI were statistically indistinguishable from their cognitively intact counterparts in terms of the amount of time spent outside the home each day, with both averaging about 4.2 hours daily.
However, during a follow-up period of more than 3 years, there was a steady decline in this measure in the adults with MCI, compared with little change in the cognitively intact participants. In the last month of monitoring, the participants with MCI left their home for 2.9 hours daily on average, which was significantly shorter than the 3.8 hours recorded for cognitively intact participants.