Gait disturbances could indicate a decline in cognitive function

Gait disturbances – such as a slowing of walking pace or a more variable stride – could indicate a decline in cognitive function, according to new research studies reported today at the Alzheimer's Association's International Conference® 2012 (AAIC® 2012).

"With an aging baby boomer generation advancing into greater risk for Alzheimer's and dementia, it is important for physicians to be aware of the associations between gait and mental function. These studies suggest that observing and measuring gait changes could be a valuable tool for signaling the need for further cognitive evaluation," said William Thies, PhD, Alzheimer's Association® Chief Medical and Scientific Officer.

"For busy doctors who have limited time with their patients, monitoring deterioration and other changes in a person's gait is ideal because it doesn't require any expensive technology or take a lot of time to assess. It is relatively simple and straightforward," Thies added.

Gait Analysis Shows that Stride Speed and Variability May Track with Cognitive Impairment

Difficulties with walking are not inevitable consequences of aging. They are, however, common and relevant problems among older adults. Research shows that people with walking difficulties not only have an increased risk of falling, but may also have an increased risk developing memory disorders and dementia.

Stephanie A. Bridenbaugh, MD, of the Basel Mobility Center in Basel, Switzerland, and colleagues used quantitative gait analysis to explore this issue. The study followed 1,153 participants (average>Basel cohort study, from 2007 to 2011.

Participants were divided into groups based on their cognitive diagnoses: cognitively healthy, mild cognitive impairment (MCI) or Alzheimer's dementia. Those with Alzheimer's dementia were subdivided into mild, moderate or severe. Gait was measured using a 10-meter-long electronic walkway with almost 30,000 integrated pressure sensors. All participants performed one "normal" walk and two different "dual tasks" – normal walking while simultaneously counting backwards out loud or while simultaneously naming animals.

The scientists found that gait became slower and more variable as cognitive decline progressed. For all groups, walking speeds were slower during dual tasking than during normal walking alone. "Those with Alzheimer's dementia walked slower than those with MCI, who in turn walked slower than those who were cognitively healthy," said Bridenbaugh.

"Mobility impairments are often associated with dementia, and some gait changes may even appear before cognitive decline can be detected by traditional testing methods. Gait analysis can simply, quickly and objectively measure walking. When problems emerge, this may provide early detection of fall risk and the earliest stages of cognitive impairment in older adults," Bridenbaugh added. "A gait analysis will not replace a comprehensive neuropsychological assessment to diagnose a patient's cognitive status. Gait analysis, however, may prove to be an important tool to aid diagnosis, and record treatment effects or disease progression."

Specific Aspects of Gait may be Associated with Specific Cognitive Abilities and Functions

With aging and in people with Alzheimer's disease, various brain functions deteriorate. Most research has focused on cognition. Recent evidence suggests that gait is also affected by aging and Alzheimer's, yet the exact relationship remains unclear.

Mohammad Ikram, MD, PhD, and colleagues at Erasmus MC, Rotterdam, the Netherlands investigated the relationship between cognition and gait in community-dwelling elderly. The researchers studied 1,232 individuals age 49 and older from The Rotterdam Study (Note: data included here is updated since the original abstract submission to AAIC 2012). Standardized neuropsychological tests were used to measure information processing speed, memory, fine motor speed, and executive function. Gait was assessed using an electronic walkway.

Each participant performed a normal walk, a tandem walk (where the heel of your front foot is placed directly touching the toes of your back foot), and a turn. Gait variables were grouped into seven independent factors:

• Rhythm (reflecting stride time and cadence)
• Pace (reflecting stride length and velocity)
• Phases (reflecting the amount of time spent on one or both feet)
• Variability (reflecting the variation in gait within persons)
• Base of Support (reflecting step width and stride width)
• Tandem (the amount of errors in a tandem walk)
• Turn (the amount of time and steps needed to turn around)

Interesting patterns emerged in the data analysis; the researchers found that certain cognitive domains were only associated with certain aspects of gait.

• Information processing speed was associated with the Rhythm aspect of gait.
• Executive function was associated with Pace and Variability.
• Fine motor speed was associated with Tandem.
• Memory was not associated with any aspect of gait.

"Our results suggest that cognition and gait are tightly linked according to a specified pattern, in which certain cognitive domains only associate with corresponding aspects of gait," Ikram said.

Reduced Gait Velocity, Cadence, and Stride Length may be Associated with Cognitive Decline

Some previous studies have reported that gait abnormalities may be associated with cognitive impairment and dementing illnesses. However, it is unclear which gait components may be associated with a future cognitive decline.

Rodolfo Savica, MD, MSc, and colleagues at the Mayo Clinic Study of Aging (MCSA) measured the stride length, cadence and velocity of more than 1,341 study participants through a computerized gait instrument (GAITRite) at two or more visits roughly 15 months apart. The visits also included neurological and neuropsychological evaluations covering four domains: memory, executive functioning, language, and visuospatial ability. Participants were either cognitively normal (1,172), or diagnosed with MCI (158) or dementia (11).

The researchers found that study participants with lower cadence, velocity and amplitude of the stride length experienced significantly larger declines in global cognition, memory and executive function.

"We observed an association between reduced gait velocity, cadence and stride length, and both global and domain-specific cognitive decline in our population," said Savica. "These results support a possible role of gait changes as an early predictor of cognitive impairment."

Continuous In-Home Monitoring may be a More Accurate Measure of Gait than Single Tests

Traditionally, walking speed has been collected at a single, intermittent time point, such as during a yearly physical exam.

"Advanced technology now allows us to measure walking speed in one's own home, derived from hundreds of walking episodes, and using information collected continuously by motion sensors," said Lisa Silbert, MD, MCR, of Oregon Health & Science University, Portland. "This potentially provides a better measure that links real-world walking abilities and brain health."

Silbert and colleagues worked with 19 dementia-free volunteers (mean MMSE 28.7) enrolled in the Intelligent Systems for Assessment of Aging Changes (ISAAC) study. All participants underwent brain MRI to measure the volume of the total brain and various brain sections. Gait speed was determined in two ways: (1) at the time of MRI, by assessing the time to walk nine meters, and (2) by using an in-home assessment system that continuously collected data over a one month period using motion activity sensors.

The researchers found that:

• Study participants walked faster when measured once in person than when walking in their home under conditions of continuous assessment.
• Slower walking speed determined with continuous in-home assessment technology was associated with smaller total brain size, while single walking speed measures were not.
• Slower in-home walking speed was more highly associated with smaller volumes of the hippocampus (a section of the brain important for memory) than walking speed obtained during a single time point.

"Walking speed taken at a single time point may over-estimate walking abilities in the elderly. Our data suggests that continuous in-home monitoring may provide a more accurate reflection of walking speed and may be more sensitive at detecting motor changes associated with future cognitive decline," Silbert said.

Gait Changes Correlate with Dementia Symptoms in an "Old-Old" Population

The Kurihara Project, conducted by Kenichi Meguro and colleagues at the Tohoku University Graduate School of Medicine, Sendai, Japan, examined the relationship between gait and cognition in 525 community dwelling persons age 75 and older in Kurihara and Osaki, Japan.

Researchers gathered participants' demographics, medical history, general medical and neurological examination results, MRI results, and neuropsychological exams including the Mini-Mental State Examination (MMSE) and the Clinical Dementia Rating (CDR). Participants walked six meters at their fastest pace. Gate measures included gait pattern, velocity and stride length.

The researchers found that 385 study participants had a normal gait pattern, 65 had "neurological gait," and 73 had abnormal gait due to bone and joint disease (such as osteoarthritis). On the CDR scale: 175 participants were classified CDR 0, 287 as CDR 0.5, 44 as CDR 1, 20 as CDR 2, and 2 as CDR 3. (CDR 0 is considered normal, CDR .5 = very mild dementia, with dementia severity increasing to CDR 3 = severe dementia.) They also found that MRI-measured atrophy of the entorhinal cortex – a section of the brain that functions as a hub in a widespread network for memory and navigation – was significantly correlated with gait velocity.

"Our research found that gait velocity was significantly decreased as the severity of dementia symptoms increased," said Meguro. "Gait should no longer be considered a simple, automatic, motor activity that is independent of cognition. They are linked."

SOURCE Alzheimer's Association