Dementia is one of the scariest risks associated with aging, affecting nearly 5.6 million Americans over the age of 65, per the Centers for Disease Control and Prevention (CDC). Currently, there is no cure for any kind of dementia, including the most common form, Alzheimer’s disease. Researchers and health experts work to help those who already have the condition, while simultaneously trying to understand how the disease presents itself—and what can be done to stave it off. One recent study points to a notable sign that could serve as a predictor of the disease, which may help healthcare providers intervene earlier. Read on to find out how your body might be telling you that you’re at risk.
Diagnosing Alzheimer’s disease presents a unique challenge, and historically, medical professionals were only been able to give a concrete diagnosis when examining a patient’s brain after death. According to the Mayo Clinic, it is now possible to diagnose the disease “with more certainty” while patients are alive, thanks to new tests that check for biomarkers, which are signs of the condition.
Clinicians and researchers can do this with PET scans—imaging tests that check for diseases—or by testing plasma or cerebral spinal fluid to measure levels of amyloid and tau proteins, both of which accumulate abnormally in the brain of Alzheimer’s disease patients. Blood tests are also on the rise, with several in development, according to the National Institute on Aging (NIH), but due to limited availability, experts continue to search for more approaches. Now, a new study has identified one risk factor that could be a less invasive approach for early diagnosis.
Losing your sense of smell is something many of us have come to fear amid the COVID-19 pandemic, as it was once one of the telltale symptoms of the virus. But loss of smell could also be an early warning sign that you’re at risk for Alzheimer’s disease.
A recent study published in the Journal of Alzheimer’s Disease provides additional evidence that loss of smell is a warning sign for mild cognitive impairment (MCI) related to Alzheimer’s disease. In fact, for every unit lower a patient scored on the Sniffin’ Sticks Odor Identification Test, the risk of developing MCI shot up by a staggering 22 percent. And while not everyone who develops Alzheimer’s has MCI, that milder cognitive decline often precedes the condition.
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Also known as anosmia, loss of smell has been identified as an early indicator of Alzheimer’s in previous studies. Data published in Biosensors in 2018 found that sense of smell worsened as patients progressed from MCI to Alzheimer’s disease. As a result, researchers suggested designating “olfactory dysfunction”—that is, disruptions to your sense of smell—as a way to identify those at risk for Alzheimer’s disease even before MCI symptoms appear (also known as the preclinical stage). Experts believe anosmia occurs because the olfactory system “has limited self-repair mechanisms,” which make it more susceptible to damage from Alzheimer’s disease.
What the new data suggests is that this loss is connected to a faster buildup of harmful proteins in the brain, namely amyloid-beta and tau, according to an NIH press release outlining findings. This may explain why the loss of smell is an early warning sign for MCI and eventually Alzheimer’s disease, as it was “closely tied” to the level and progression of neuropathological damage.
To evaluate the association between olfaction with MCI and protein deposition, researchers studied 364 patients from the Baltimore Longitudinal Study of Aging, all of whom were cognitively normal at baseline. At the start of the study, patients were given odor identification tests as well as PET scans, which are used to detect the amount of amyloid-beta and tau in the brain.
Over the course of 2.5 years, 17 study participants (5 percent) were diagnosed with mild cognitive impairment. Of these patients, 11 cases were associated with Alzheimer’s disease, three with vascular dementia, and one with frontotemporal dementia. The remaining two were “unspecified based on clinical characteristics,” the press release stated.
When looking at these patients’ PET scans, those with lower olfactory scores had higher levels of Alzheimer’s pathology in their brains, and those whose sense of smell declined over time also had higher amyloid and tau levels in some regions related to smell and memory function. Further research, however, is required to predict other neurodegenerative changes related to dementia, investigators said.