Also, Preliminary Results on a Possible New "Eye Test" for Alzheimer's
Falls are more common among individuals with the earliest signs of Alzheimer's, according to a study presented at the Alzheimer's Association® International Conference 2011 (AAIC 2011). The study measured the rate of falls among cognitively healthy older adults with and without preclinical Alzheimer's – as measured by amyloid imaging using positron emission tomography (PET) with Pittsburgh compound B (PiB) – and found twice the risk of falls for people with higher levels of PiB on their scan.
In older adults, falls contribute to increased disability, premature nursing home placement and injury-related mortality. There are also higher health care costs associated with falls – more than $19 billion could be attributed to the direct medical costs of falls in 2000. Older adults with Alzheimer's may be at higher risk for falls because of balance and gait disorders and problems with visual and spatial perception that are caused by the disease.
"Understanding the traditional hallmarks of Alzheimer's, including cognitive impairment and memory loss, are important; however, these study results also illustrate the significance of understanding that, in some people, changes in gait and balance may appear before cognitive impairment," said Maria Carrillo, Ph.D., Alzheimer's Association Senior Director of Medical and Scientific Relations.
"Growing scientific evidence suggests that 'silent' biological changes may be occurring in the brain a decade or more before we can see the outward symptoms of Alzheimer's. According to this study, a fall by an older adult who otherwise has a low risk of falling may signal a need for diagnostic evaluation for Alzheimer's," continued Carrillo.
Led by Susan Stark, Ph.D., Assistant Professor of Occupational Therapy and Neurology at Washington University in St. Louis, the 8-month study followed 125 older adults currently enrolled in longitudinal studies of memory and aging at Washington University's federally funded Knight Alzheimer's Disease Research Center (ADRC). All participants had PiB PET imaging and contributed samples of cerebrospinal fluid (CSF). Each participant was asked to record in a journal how many times they experienced a fall, which was defined as unintentional movement to the floor, ground or an object below knee level. Some of participants had preclinical Alzheimer's and some did not. With an average of 191 days of data collected for participants, the study found that 48 people experienced at least one fall. A positive PiB PET image resulted in a 2.7 times greater risk of a fall for each unit of increase on their PiB PET scan.
"To our knowledge, this is the first study to identify a risk of increased falls related to a diagnosis of preclinical Alzheimer's disease," said Stark. "This finding is consistent with previous studies of mobility problems among persons with very early symptomatic Alzheimer's or mild cognitive impairment. It suggests that higher rates of falls can occur very early in the disease process."
"In the near future, with continued research, we will improve our ability to detect and intervene early in Alzheimer's disease. With earlier detection, perhaps we can also lower the risk of falls, which can be disabling, expensive and even deadly in older adults," said Carrillo. "Additional research is urgently needed, for example to further explore the connection between motor deficits and falls as possible early signals of Alzheimer's."
Retinal Imaging May Prove Useful In Identifying Individuals at Risk for Alzheimer's
Another study featured at AAIC 2011 explored whether characteristics of blood vessels in the retina (the light-sensitive layer at the back of the eye) might serve as possible biomarkers for Alzheimer's disease. While most Alzheimer's-related pathology occurs in the brain, the disease has also been reported to create changes in the eye, which is closely connected to the brain, and more easily accessible for examination in a doctor's office.
"Today, there is no single method for detecting Alzheimer's until the disease is well advanced. Current PET and MRI scans can detect some brain changes, but these procedures can be expensive and technically challenging, and so are impractical for testing in large populations," said Shaun Frost, MSc, of CSIRO's Australian e-Health Research Center.
In a small pilot study, Frost and colleagues examined retinal photographs of people with Alzheimer's.
They found that the width of certain blood vessels in the back of the eye were significantly different for people with Alzheimer's vs. healthy controls, and that this correlated with a brain imaging benchmark indicative of Alzheimer's disease – the deposition of amyloid plaque in the brain as measured by PET PiB imaging.
"Our studies are very preliminary, but encouraging," said Frost. "Since amyloid plaque build up in the brain occurs years before cognitive symptoms of Alzheimer's are evident, a non-invasive and cost-effective retinal test may hold promise as an early detection tool for the disease. We hope that, in the future, our measure could be used with blood-based tests to help doctors identify who needs further assessment with PET imaging and MRI for Alzheimer's, but more research is needed."
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