Subtle changes in the way a person walks can be an early warning sign of cognitive decline and a signal for advanced testing, according to research out today at the Alzheimer's Association International Conference 2012.

The findings are the first to link a physical symptom to disease, which up until now, required doctors to begin a diagnosis by focusing on cognition and administering lengthy neurological exams. The evidence in the five studies is "robust," say experts, adding walking changes can occur even before cognition decline surfaces. The presentation on the opening day of the weeklong meetings follows a government plan announced in May to help train doctors to detect the disease earlier and to find a cure by 2025.

"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,'' says Bill Thies, chief medical and scientific officer for the Alzheimer's Association.

The disease affects 5.4 million mostly older people in the USA, numbers expected to spike to 16 million in 2050 as the Baby Boomers age. Nearly 5,000 researchers are attending the meetings in Vancouver, where dozens of studies will address new treatments currently being tested in trials and how lifestyle influences the disease.

"Walking and movements require a perfect and simultaneous integration of multiple areas of the brain,'' says Rodolfo Savica, author of a study done at the Mayo Clinic in Rochester, Minn.

Walking changes occur because the disease interferes with the circuitry between these areas of brain. Savica ruled out other diseases (Parkinson's, arthritis) as possible causes of gait change.

In the Mayo Clinic study, researchers measured the stride length, cadence and velocity of more than 1,341 participants through a computerized gait instrument at two or more visits roughly 15 months apart. They found that study participants with lower cadence, velocity and length of stride experienced significantly larger declines in global cognition, memory and executive function.

"These changes support a possible role of gait changes as an early predictor of cognitive impairment,'' Savica says.

Another large study of 1,153 adults with a mean age of 78 done by researchers at the Basel Mobility Center in Basel Switzerland found gait became "slower and more variable as cognition decline progressed.''

Participants were divided into groups based on their cognitive diagnoses: cognitively healthy, mild cognitive impairment (MCI) or Alzheimer's dementia. Gait was measured using a walkway with nearly 30,000 integrated sensors.

"Those with Alzheimer's dementia walked slower than those with MCI, who in turn walked slower that those who were cognitively healthy,'' says Stephanie Bridenbaugh, lead researcher.

Bridenbaugh says analysis of walking could also be used to show if treatments to treat the disease are working.

"At the annual wellness visit required by Medicare, a physician could add a walking test to the checklist without adding a lot of extra time,'' says Thies.

Yet, one of the study's researchers said that one annual test wouldn't work with everyone.

"You'd be surprised how many people say to me 'He doesn't walk that well at home,' when I give them a gait test in the office,'' says physician Lisa Silbert.

Silbert conducted research on 19 dementia-free volunteers enrolled in the Intelligent Systems for Assessment of Aging Changes study at Oregon Health and Science Univeristy in Portland. They measured gait speed during MRIs and gait speeds at home. Partipants walked faster when measured once in person than when walking in their home. Slower in-home walking speed was associated with smaller total brain size. Dementias cause brain shrinkage.

"Walking speed taken at a single time point may overestimate the walking abilities in the elderly,'' she says.

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