Resulting from the degeneration and death of brain cells, Alzheimer’s disease is the most common cause of dementia — that is, cognitive decline severe enough to interfere with one’s day-to-day life. It is a “fast-moving, aggressive disease” that affects women more than men — making it crucial to develop tests to predict it as early as possible.

Published in Nature’s Molecular Psychiatry, the study by a team of Swedish researchers compared how different biomarkers for Alzheimer’s fare in predicting the risk and progression of the disease.

“There’s been a rapid development of different Alzheimer’s biomarkers in recent years, enabling us to measure and detect early signs of the disease in patients… But we still need to find tests that can predict the development of the disease with greater specificity, so that we can improve not only its diagnosis but also its prognosis and treatment,” Marco Bucci from the Center for Alzheimer Research at Karolinska Institutet in Sweden, who led the study, told the press.

Bucci and his team focused on beta-amyloid and tau — two proteins that “go rogue and destroy brain cells” in people with Alzheimer’s. This results in memory problems, as well as trouble thinking and reasoning.

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“[U]ntil a few years ago, the levels of these proteins in a person with Alzheimer’s could only be measured after the person had died,” Bucci wrote in The Conversation. “Today, we can measure these levels in living people using two methods: examining a sample of cerebrospinal fluid (the clear liquid that surrounds the brains and spinal cord) [and a form of] brain scans,” he added.

Essentially, through a medical procedure known as a “spinal tap,” which involves the insertion of a needle into a person’s spinal canal to collect cerebrospinal fluid, medical practitioners can assess a patient’s risk of developing Alzheimer’s. At present, the procedure is already used to diagnose cancers of the brain or spinal cord, and different disorders of the central nervous system like Guillain-Barre syndrome and multiple sclerosis.

However, Bucci notes that the brain scan is an even more accurate method to predict the development of Alzheimer’s. The PET scan, an imaging test, provides insights into the presence of tau in the brain, which was found to be linked to a rapid decline of episodic memory, or the “memory of everyday events that can be explicitly stated or conjured.”

The researchers tested both methods on a group of 282 participants, and their results demonstrated the greater accuracy of the brain scan over the spinal tap. “Episodic memory is often affected at an early stage of the disease, and our study suggests that looking for tau using PET scans is the best way to predict early-stage Alzheimer’s,” Bucci writes.

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Last month, yet another study involving researchers from the U.S. also reached a similar conclusion regarding the usefulness of PET scans in the early diagnosis of Alzheimer’s. “[T]au PET imaging biomarkers can predict future decline in individuals… These tau-based biomarkers may help predict the pace of progression of the disease and be important for early detection. They may eventually help us treat [Alzheimer’s] before we see symptoms,” Emily Rogalski, associate director of Northwestern Medicine’s Mesulam Center for Cognitive Neurology and Alzheimer’s Disease, who had co-authored the study, said in a statement.

The fact that brain scans are non-invasive, unlike a spinal tap, makes this news even greater.

Bucci believes the tau PET “should be recommended” for assessing potential cognitive decline. But that’s not all. “Our findings show that the concentration of tau in the brain in Alzheimer’s disease plays an important part in its pathological progression and may become a key target for future drug treatments,” said Agenta Norberg, a neuroscientist at Karolinska Institutet, and co-author of the present study.

However, Bucci expressed hopes that more specific tau tracers in the future can make the diagnostic assessment even more accurate, which is exactly the need of the hour. “By 2050, the number of people with Alzheimer’s disease in India is expected to triple from what it is now; most new cases will be among the generation reading this article now; most patients will be women,” The Swaddle had reported in 2019.