FROM JAMA NEUROLOGY

Poor performance in dual-task gait testing was significantly associated with dementia progression in patients with mild cognitive impairment (MCI), according to a small prospective study.

The dementia prediction model could provide clinicians with a minimally invasive, low-cost analysis tool for patients with MCI and a compass to help guide decisions for further testing, according to Manuel Montero-Odasso, MD, PhD , an associate professor at the University of Western Ontario, London, and his colleagues.

In a study of 112 patients with MCI who were part of the Gait and Brain Study, investigators measured patients’ walking speed while only focusing on walking and then again while walking and counting backward from 100 by ones, counting backward from 100 by 7, or naming animals. The percentage difference between patients’ single-test walking speed and the dual-task speed was the dual-task gait cost. Patients received a biannual follow-up over a 6-year period.

Investigators found that higher gait costs in the dual gait test involving either counting backward by ones or naming animals were associated with a significantly increased risk of progression to dementia (JAMA Neurol. 2017 May 15. doi: 10.1001/jamaneurol.2017.0643 ).

“Our sensitivity analysis showed that dual-task gait was comparable with cognitive testing to predict incident dementia,” said Dr. Montero-Odasso. “Clinicians may use dual-task gait testing in screening patients with MCI who could benefit the most from additional testing, optimizing recommendations for imaging, spinal fluid examinations, and genetic testing.”

Patients were an average of 75 years old, with an even distribution of men and women. Patients had an average of five comorbidities, most common among them hypertension (60.4%) and history of smoking (56.1%). Of the 112 participants, 24% progressed to dementia, an incidence rate of 121 per 1,000 person-years. A total of 39% of the study participants carried an APOE e4 allele.

Investigators confirmed the presence of MCI by evaluating patients’ levels of cognitive challenges, impairment in memory, executive function, attention, language, certain living activities, and an absence of dementia using criteria from the Diagnostic and Statistical Manual of Mental Disorders, fourth edition.

When comparing the three dual-task gait tests, researchers found that higher gait cost when asking patients to count backward by ones or name animals presented a 3.8 times (P = .003) and 2.4 times (P = .04), respectively, increased risk of dementia progression. Gait cost when counting from 100 by sevens wasn’t significantly associated with dementia risk.

The researchers said that they still do not understand completely the relationship between walking velocity and cognitive function, although they hypothesized the connection may have to do with shared networks in the brain.

“What does seem clear is that executive demands used for gait and for the selected cognitive tasks may share a similar pathogenic mechanism at the brain level,” according to Dr. Montero-Odasso and his fellow investigators. “Episodic memory, a cognitive domain that was affected in all of our participants who progressed to dementia, relies on frontal-hippocampal circuits that are also central for gait control.”

The study was limited by the small population size, causing investigators to conclude that their findings are only generalizable at a clinic-based level. The investigators also noted the need for cross-validation in other MCI cohorts.

The model would be accessible for clinicians and researchers alike when identifying high-risk patients, designing further testing strategies, or planning primary prevention or intervention studies by more easily selecting patients with a greater risk of dementia progression, Dr. Montero-Odasso and his peers asserted.

The Canadian Institutes of Health Research funded the study. One of the authors reported having been a part-time employee of Pfizer and owning employee stock options. The investigators reported no other relevant financial disclosures.

ezimmerman@frontlinemedcom.com

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