With current therapies being unable to treat Alzheimer’s disease (AD) once symptoms appear, early detection has become the holy grail for managing the neurodegenerative disease. A promising biomarker that allows for early detention of Alzheimer’s is an abnormal amount of amyloid-β and tau protein deposits in the central nervous system, which is detectable many years prior to symptom onset.
The urgency around finding a predictive test has grown from the disease’s large and multifaceted impact. Alzheimer’s affects one in ten people over the age of 65, and the CDC expects rates of the disease to nearly triple over the next 40 years, affecting about 14 million Americans. The burden of the disease weighs heavily on the shoulders of caregivers, tax payers, and hospitals alike. In 2019, the disease is estimated to cost $290 billion nationally, the majority of which will come from Medicare and Medicaid. Older adults with AD are more likely than those without the disease to rack up multiple hospital visits, nursing facility stays, and home visits. And all of this says nothing of the emotional burden stemming from the devastating symptoms that patients and their loved ones must confront.
Previous research has examined the utility of testing for biomarkers in spinal fluid and imaging the eye's retina for clues about a person’s AD risk, but these tests are not without their limitations. For example, the spinal fluid used in some AD tests must be obtained through a lumbar puncture, an invasive and expensive procedure that can be painful for patients during and after the procedure. The retina imaging scan is encouraging, but needs more study to determine whether abnormalities in the eye are due to preclinical AD or an undiagnosed eye disease.
New research from Boston Medical Center (BMC), published in the Journal of Alzheimer’s Disease, points toward the possibility of a more accessible test for detecting AD risk before symptom onset.
Researchers examined amyloid-β and tau protein levels in eye fluid that’s extracted — and typically discarded — during certain eye surgeries. None of the participants had an AD diagnosis. Lower levels of these biomarker proteins were significantly associated with lower scores on a nondiagnostic test of the corresponding patient’s baseline cognitive function. The research is the first study to connect these known AD biomarkers in the eye to mental status.
“The findings could help us build an accessible and minimally invasive test to determine Alzheimer’s disease risk, especially among patients with eye disease,” says Lauren Wright, MD, first author on the study and ophthalmology fellow at BMC.
These results also reaffirm previous research suggesting that patients with eye disease are at-risk for the development of AD, and suggest that further investigation in patients with eye disease may yield results that could be generalizable to larger populations.
“This is a great step in discovering the eye’s potential role in diagnosing preclinical Alzheimer’s disease, and further study is needed comparing protein biomarkers in the eye with more in-depth neurological testing,” adds Manju Subramanian, MD, senior author, principal investigator, and ophthalmologist at BMC.