Finally, an accurate blood test for Alzheimer’s at its earliest stages could be on horizon

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NEW YORK — When Dr. Alois Alzheimer first identified the disease that would bear his name in 1906, he could only confirm his diagnosis by examining brain tissue after a patient’s death. More than a century later, we still lack simple, reliable ways to detect this devastating condition in its early stages. But a new study suggests that two naturally occurring molecules in our blood could change that, and help explain one of the disease’s most puzzling aspects: why it affects women so much more frequently than men.

The study, published in Molecular Psychiatry,, reveals that declining levels of two molecules — acetyl-L-carnitine (LAC) and its derivative free carnitine — track closely with worsening cognitive symptoms. With an estimated six million Americans currently living with some form of Alzheimer’s disease, most over age 65 and predominantly women, this discovery could transform how we diagnose and monitor this condition.

“Our findings offer the strongest evidence to date that decreased blood levels of acetyl-L-carnitine and free carnitine could act as blood biomarkers for identifying those who have Alzheimer’s disease, and potentially those who are at greater risk of developing early dementia,” explains study lead investigator Betty Bigio, PhD, research assistant professor in the Department of Psychiatry at NYU Grossman School of Medicine, in a statement.

These molecules serve as more than just markers: they play crucial roles in how our brain cells function. Think of them as cellular fuel gauges, monitoring and maintaining the power plants (mitochondria) within our neurons. When these levels drop, it may signal trouble ahead, particularly for women.

In their comprehensive analysis of 125 participants across two independent study groups, researchers found that women with cognitive impairment showed significantly lower levels of free carnitine compared to cognitively healthy women. These levels declined progressively as their condition worsened. Surprisingly, this pattern was largely absent in men, who showed declines only in LAC levels but not free carnitine.

“Because declines in acetyl-L-carnitine and free carnitine tracked closely with the severity of Alzheimer’s disease, the molecular pathways involved in their production offer other possible therapeutic targets for getting at the root cause of the disease and potentially intervening before permanent brain damage occurs,” notes senior study investigator Carla Nasca, PhD, assistant professor in the Departments of Psychiatry and Neuroscience at NYU Grossman School of Medicine.

The potential for a blood-based diagnostic test represents a significant advance over current methods that rely on more invasive procedures like spinal taps, which carry risks of pain and infection. When researchers combined these blood markers with traditional spinal fluid measures, their accuracy in diagnosing Alzheimer’s disease rose to an impressive 93%.

Previous research has shown that LAC serves as a molecular shuttle, transporting crucial molecules from mitochondria to the cell nucleus, enabling gene activation. This process is particularly important for regulating genes that produce glutamate, a neurotransmitter involved in most brain activities, including nerve cell repair. Understanding these mechanisms could lead to new therapeutic approaches.

These findings could potentially be helpful for ailments beyond just Alzheimer’s disease. The research team has previously linked deficiencies in acetyl-L-carnitine to depression and childhood trauma. Future investigations will explore how to prevent the progression from depression to Alzheimer’s disease.

These discoveries open new possibilities for early intervention and personalized treatment approaches. A blood test could help predict the effectiveness of potential new drug treatments designed to delay or prevent Alzheimer’s onset. It might also provide a more objective, quantitative measure of disease severity than existing questionnaires that test memory or thinking skills.