Representative brain SPECT scans in a patient with Alzheimer’s dementia showing substantially reduced brain blood flow in the temporal and parietal lobes compared to a person with depression with mild decreased frontal lobe blood flow. [Image from Journal of Alzheimer’s Disease]
The study examined 4541 people in total — 847 with dementia, 3269 with depression and 425 with both. SPECT imaging measures the blood flow and activity in the brain and the researchers saw that people with cognitive disorders had reduced blood flow in the hippocampus, temporal and parietal lobes of the brain. With 86% accuracy, SPECT imaging could tell the difference from a cognitive disorder and depression. It can also distinguish depression or dementia in people with both conditions with 83% accuracy.
“This is a critical clinical question that has practical implications for patient management and treatment,” said Dr. Daniel G. Amen, lead researcher, psychiatrist, and director of the Amen Clinics, in a news release. “These disorders have very different prognoses and treatments and being able to improve diagnostic accuracy can improve outcomes for some patients.”
Amen has been a major proponent of SPECT over the years, though he has been criticized for being over-promotional.
Depression affects more than 300 million people worldwide, according to the World Health Organization. Other methods for diagnosing depression include a physical exam, blood tests or psychological evaluation, and a mental health professional may use information from the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) to diagnose someone. Doctors also use the Beck’s Depression Inventory questionnaire that asks a patient to rate how they’re feeling on a scale of 0 to 3 on a variety of questions.
To diagnose a cognitive disorder, doctors look at the patient’s medical history, independent function and daily activities, consult a family member or friend, evaluate their mental status, perform a neurological exam, evaluate their mood and perform lab tests. The Alzheimer’s Association suggests that 15-20% of those who are 65 years or older may have some form of mild cognitive impairment.
The Beck’s Depression Inventory questionnaire makes it harder to tell the difference between someone with depression and someone with a cognitive disorder because the symptoms overlap, according to the study.
“One of the greatest new insights of the past decade is the linkage of depression to the psychology of late-life cognitive decline. Raji and coworkers extend the approach to the biological substrate by an elegant imaging approach. These studies further place brain aging on a firm biological basis,” said George Perry, PhD, editor-in-chief of the Journal of Alzheimer’s Disease and dean and professor of biology at the University of Texas at San Antonio.
The study was published online in the Journal of Alzheimer’s Disease.
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