Motoric cognitive risk syndrome (MCR), a newly developed diagnosis that incorporates cognitive symptoms and slow gait in patients without dementia or mobility-related disability, is common in older adults and is an early risk factor for cognitive decline, a new study suggests.
The research found that the pooled prevalence of MCR among older adults from countries around the world is 9.7%, with prevalence being similar in both men and women, but higher in those older than 75 years.
The research also revealed that those with MCR are about twice as likely as those without this diagnosis to develop dementia.
"There are other predementia syndromes that have been identified, but almost all of them rely on cognitive testing or biomarkers or doing imaging studies, and these procedures may not be practical in many clinical settings around the world that have few resources," said lead study author Joe Verghese, MBBS, professor, Department of Neurology and Medicine, Albert Einstein College of Medicine, and chief, geriatrics, Einstein and Montefiore Medical Center, Bronx, New York.
A recently described predementia syndrome, MCR is diagnosed with simple questions about memory and accessible ways to measure gait speed, such as using a stop watch to time walking over a fixed distance, said Dr. Verghese.
Dr. Joe Verghese
The study was published online July 16 in Neurology.
Pooled Prevalence
The analysis included 26,802 older adults (mean age, 71.6 years) from 22 cohorts in 17 countries: 7 North American, 6 European, 5 Asian, 2 African, 1 Israeli, and 1 Australian. Slightly more than half the sample (55.7%) were women and the mean duration of education was 6.9 years.
MCR is diagnosed independent of cognitive tests. In the studies included in this analysis, cognitive problems were ascertained from standardized questionnaires.
Gait speed was measured quantitatively as well as timed over a fixed distance. Slow gait was defined as a walking speed of 1 standard deviation below age- and sex-specific means individualized to each cohort. Mean gait speed in the analysis was 81.8 cm/s.
Participants with MCR had worse performance on all cognitive tests than those without MCR, as well as a higher prevalence of vascular and nonvascular disease. Higher education (12 or more years) was associated with reduced risk for MCR, a finding that "needs further scrutiny to gain insights into potential interventions," the authors write.
Pooled prevalence of MCR among the 26,802 participants was 9.7% (95% confidence interval, 8.2% - 11.2%). MCR prevalence was higher among those aged 75 and older (10.6%) than in those aged 60 to 74 years (8.9%). Prevalence of MCR was similar in men and women.
The lowest MCR prevalence was in the Australian (2%) and United Kingdom (2%) studies that recruited ambulatory seniors with high walking speeds. The highest prevalence was in French (16%) and Indian (15%) cohorts that enrolled seniors with cognitive symptoms.
The researchers looked at MCR and risk for cognitive impairment, defined as a change in score of 4 or more on the Mini-Mental State Examination (MMSE) during follow-up In 4 studies. Three of these studies were from the United States (Hispanic Established Populations for Epidemiologic Studies of the Elderly [H-EPESE], Memory and Aging Project [MAP], and Religious Orders Study [ROS]) and 1 was Italian (Inveocchiare in Chianti [InCHIANTI]).
In this analysis, MCR predicted incident cognitive impairment in all cohorts with adjusted hazard ratios (aHRs) ranging from 1.48 to 2.74.
The researchers did an analysis that excluded participants who met incident cognitive impairment criteria in the first 3 years to, as Dr. Verghese explained, rule out people with early dementia misdiagnosed as having MCR. MCR still predicted incident cognitive impairment (aHR, 1.71).
"You would expect that the people who actually have dementia but are being classified as MCR would meet dementia criteria pretty soon over the next 2 or 3 years, but if you take them out, that would suggest that MCR can predict beyond the initial few years and capture cases that are going to develop dementia more than 3 years out," said Dr. Verghese.
MCR also predicted incident cognitive impairment when the analysis was restricted to those with baseline MMSE scores of 28 or more (aHR, 1.65).
MCR was associated with increased risk for Alzheimer disease (AD) dementia in the 2 cohorts that included this subtyping: MAP and ROS, which together included more than 2000 participants. This finding was "surprising" given that in an earlier cohort (the Einstein Aging Study), MCR predicted vascular dementia but not AD, said Dr. Verghese.
Unfortunately, in this new analysis, the studies didn't have vascular subtyping, "so we couldn't say if MCR also predicted vascular dementia", added Dr. Verghese.
"The high agreement in MCR prevalence defined multiple ways and excluding subgroups is reassuring," commented the authors, who also stressed that the association of MCR with clinical dementia subtypes "needs to be further verified."
Enlarging the Pool
Identifying MCR has numerous benefits, Dr. Verghese said. It identifies a group of older adults not encompassed by other predementia syndromes, "so you're enlarging the pool of people, or capturing the people who might not be identified otherwise."
Gait speed has a common metric, high reliability between different protocols, and excellent validity in predicting health outcomes, he noted. And, unlike neuropsychological, laboratory, and imaging tests that can detect predementia syndromes, gait speed testing is readily available and practical in most settings.
From a clinician's point of view, the MCR is attractive because of its simplicity, said Dr. Verghese. It doesn't even have to be a doctor using the tool; it could be a nurse, receptionist, or worker out in the field.
The MCR approach "can help streamline high-risk individuals for further investigation, especially in resources-poor settings," noted the authors.
A limitation of the study was that it wasn't totally global and slow gait might vary regionally. However, said the authors, representing all counties may not be feasible.
Gait speed may not be the strongest motoric predictor of dementia, although there's limited information on the predictive validity of other motoric signs for dementia, for example tone or strength.
As well, dementia prevalence may be underestimated with criteria used in the participating studies, particularly in low- and middle-income countries.
Dr. Verghese said he hopes the MCR diagnosis will eventually be used widely — in both developed and developing countries — although it's "still too early" for use in daily clinical practice. "It takes time for these concepts to percolate through the clinical world; clinicians don't change very easily."
Low Cost, Easy to Perform
Asked to comment, Pinky Agarwal, MD, a neurologist and associate clinical professor, University of Washington, Seattle, said identifying predementia is important for both clinical and economic reasons.
"The current recommended cognitive, laboratory, and radiological tests need access to facilities and are very expensive for people in low-income countries and for people with limited insurance in higher-income countries. These tests are also often denied payment by insurance companies."
Not only is the proposed method for identifying predementia "low cost," but it's also easy to perform in a wide variety of settings, said Dr. Agarwal.
No targeted funding is reported for the pooled analysis performed in this study. The authors have disclosed no relevant financial relationships.
Neurology. Published online July 16, 2014. Abstract
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Cite this: Slow Gait, Cognitive Complaints Predict Cognitive Decline - Medscape - Jul 30, 2014.
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