News From the Alzheimer’s Association 2011 International Conference in Paris
Falls May Indicate the Earliest Stages of Alzheimer’s Disease
Falls are more common among persons with the earliest signs of Alzheimer’s disease, according to study results.
Investigators measured the rate of falls among cognitively healthy older adults with and without preclinical Alzheimer’s disease—as measured by amyloid imaging using 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. Older adults with Alzheimer’s disease 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 disease, 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, PhD, Senior Director of Medical and Scientific Relations for the Alzheimer’s Association.
“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 disease,” continued Dr. Carrillo. “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 disease.”
Led by Susan Stark, PhD, Assistant Professor of Occupational Therapy and Neurology at Washington University in St. Louis, the researchers conducted the eight-month study that followed 125 older adults currently enrolled in longitudinal studies of memory and aging at Washington University’s Knight Alzheimer’s Disease Research Center (ADRC). All participants had PiB PET imaging and contributed samples of CSF. Each subject was asked to record in a journal the number of times that he or she experienced a fall, which was defined as unintentional movement to the floor, ground, or an object below knee level. Some participants had preclinical Alzheimer’s disease, while others did not. With an average of 191 days of data collected for participants, the researchers 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 the 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 Dr. Stark. “This finding is consistent with previous studies of mobility problems among persons with very early symptomatic Alzheimer’s disease 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 Dr. 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 disease.”
Retinal Imaging May Help Identify Persons at Risk for Alzheimer’s Disease
Researchers explored whether characteristics of blood vessels in the retina might serve as possible biomarkers for Alzheimer’s disease. Although 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.
“Today, there is no single method for detecting Alzheimer’s until the disease is well advanced,” said Shaun Frost, MSc, of CSIRO’s Australian e-Health Research Center. “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,”
In a small pilot study, Mr. Frost and colleagues examined retinal photographs of patients with Alzheimer’s disease (n = 13), patients with mild cognitive impairment (n = 13), and healthy participants (n = 110) from the larger Australian Imaging, Biomarker, and Lifestyle (AIBL) Flagship Study of Ageing. They examined a variety of parameters, including the width of retinal blood vessels.
The investigators found that the width of certain blood vessels in the back of the eye was significantly different for patients with Alzheimer’s disease versus 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 Mr. Frost. “Since amyloid plaque build-up in the brain occurs years before cognitive symptoms of Alzheimer’s disease are evident, a noninvasive 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 disease, but more research is needed.”