The death rate appears to be higher in persons with mild cognitive impairment (MCI), a precursor of Alzheimer disease, than in those who are cognitively normal.
“Our study results support previous findings that MCI is associated with an increased death rate. However, we added new information by looking at all MCI types and the extent of cognitive domains involved. Both amnestic (with memory impairment) and nonamnestic (without memory impairment) types of MCI and both single and multiple cognitive domains are associated with increased mortality,” lead author Maria Vassilaki, MD, PhD, a research fellow with the Mayo School of Graduate Medical Education, Department of Neurology, Mayo Clinic, in Rochester, Minnesota, told ConsultantLive before her presentation at the American Academy of Neurology annual meeting in Philadelphia.
Dr Vassilaki and colleagues, including principal author Ronald Petersen, MD, and one of the co-investigators, Dr Rosebud Roberts, studied 862 persons with MCI and 1292 without MCI who were between age 70 and 89 years and enrolled in the Mayo Clinic Study of Aging. Participants were given tests at the start of the study and every 15 months to assess their thinking abilities and were monitored for nearly 6 years.
Over 6 years, 331 of the MCI group and 224 of the non-MCI group died. The death rate was 80% higher in those who had either type of MCI during the study than in those without MCI. The death rate was more than twice as high in persons who had MCI with no memory loss during the study than in those without MCI; the death rate was 68% higher in persons with MCI and memory loss during the study than in those without MCI.
Risk factors for MCI, such as type 2 diabetes mellitus, heart disease, and stroke, could contribute to increased mortality in MCI, noted Dr Vassilaki. “MCI is associated with damage to the neurons in the brain,” she said. “It is possible that this damage could reduce brain function in general and thereby contribute to the increased mortality.”
It is yet unknown why there was a stronger association with nonamnestic MCI than with amnestic MCI. “It is possible that differences in etiology of the MCI types and differences in patterns of progression may contribute to the differences in mortality,” Dr Vassilaki said. “In addition, other comorbidities related or unrelated to MCI in the elderly could account for the differences in mortality.”
The researchers have just retrieved data on the causes of death and will compare underlying causes of death in the different MCI subgroups and those without MCI. “This might shed some light on why individuals with MCI have an increased mortality, and why individuals with nonamnestic MCI have a higher mortality than amnestic MCI,” Dr Vassilaki said.
In addition, the researchers will continue to monitor the study participants to see whether there are any long-term differences in death rates.
“As of now, clinicians follow MCI patients because of their higher risk for dementia,” Dr Vassilaki said. “ Our current research findings suggest a need for increasing awareness of higher mortality rates associated with MCI. This could lead to greater vigilance in the evaluation of all types of MCI patients and may result in timely management of any health issues that might arise.” She added,”We need to focus on reducing MCI risk factors so as to prevent the condition from developing.”