Patients with mild cognitive impairment were 80% more likely to die over a 6-year period than cognitively normal patients.
The risks were significantly elevated for both patients with amnestic and nonamnestic mild cognitive impairment (MCI), Dr. Maria Vassilaki and her colleagues reported in a study released April 23 in advance of the annual meeting of the American Academy of Neurology.
Dr. Maria Vassilaki
"Our findings build on the previous awareness of the higher mortality rate associated with MCI [mild cognitive impairment] and could promote greater vigilance in the management of these patients, enhancing timely management of any medical issues that might arise," said Dr. Vassilaki of the Mayo Clinic, Rochester, Minn. "In parallel, this information could serve as a reminder to individuals diagnosed with MCI to consult promptly with their health care team in any instances where health-related issues arise."
The findings were from a substudy of the Mayo Clinic Study on Aging (Neuroepidemiology 2008;30:58-69). The study accrued information on more than 2,000 residents of Olmstead County, Minn., who were aged 70-89 years at the time of enrollment.
Over a median follow-up of about 6 years, 331 of the 862 subjects with MCI died as did 224 of the 1,292 cognitively normal subjects.
Mortality was significantly increased whether the subjects later developed dementia (hazard ratio, 1.47). But it was much higher among those who had amnestic MCI than among the nonamnestic group (HR, 1.68 and 2.26, respectively).
"We still need to continue the research for a longer follow-up period to see whether such differences in death rates persist," Dr. Vassilaki said in an interview. "We also need to understand the factors that lead to greater mortality in individuals with MCI and to determine why individuals with nonamnestic MCI had a higher mortality rate than [did] those with amnestic MCI, compared with cognitively normal individuals."
The causal relationship is still under investigation, she said.
"There is another step to this investigation underway, to look at the causes of death. We just retrieved data on the underlying causes of death and will compare those in the different MCI subgroups and in cognitively normal individuals. This might shed some light," Dr. Vassilaki said.
She noted that previous studies have reported that individuals with MCI (either with amnestic MCI or nonamnestic MCI, depending on what the study investigated) were more likely to have dementia as an underlying cause of death, compared with cognitively normal individuals.
Dr. Vassilaki noted that Dr. Ronald Peterson and Dr. Rosebud O. Roberts are primary investigators on the Mayo Clinic Study on Aging.
She reported having no financial conflicts of interest. The study was supported with a grant from the National Institute on Aging.
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