Spanish researchers at the CSIC Institute of Biomedical Research of Barcelona believe that they may have identified a biological marker that could detect Alzheimer’s disease at least a decade before symptoms appear. A verifiable test would enable scientists to design studies for treatment of the disease in its earliest stages.

Worldwide, researchers have been working to address this challenge, as no accurate way to diagnose Alzheimer’s disease currently exists. The only way to precisely identify the disease is through post-mortem brain analysis. The Centers for Disease Control and Prevention estimates that as many as five million Americans currently have the disease, though scientists do not understand its cause. Risk factors include family history and genetics as well as past head trauma, yet the greatest of all is age. The likelihood of developing Alzheimer’s doubles about every five years after age 65.


To identify a biological marker, the investigators analyzed the cerebrospinal fluid of symptomatic patients who already showed biochemical evidence of the disease, such as decreased beta-amyloid or increased tau in the spinal fluid, signs which appear later in the progress of the disease. Scientists do not understand whether these known indications cause or are a result of Alzheimer’s disease; they only know that they are linked to it. In the samples of cerebrospinal fluid, the investigators discovered low levels of mitochondrial DNA (mDNA), the genetic material present in the energetic motor of cells. The same result was duplicated among another cohort of patients as well as with a third group of young patients with a genetic mutation that causes early-onset Alzheimer’s.

Symptomatic and asymptomatic patients alike showed reduced levels of mitochondrial DNA in their spinal fluid, suggesting the pathology of the disease begins far earlier than previously thought.

"This discovery may enable us to search for more effective treatments that can be administered during the preclinical stage," Professor Ramon Trullas, who led the research study, told the Daily Mail.

The researchers noted that it is necessary to verify these results in other laboratories to properly assess the potential to effectively diagnose Alzheimer’s before clinical symptoms appear. Trullas and his colleagues believe that lower levels of mitochondrial DNA may reflect the diminishing ability of these power stations to provide energy for brain cells.

Source: Podlesniy P, Figueiro-Silva J, Llado A, et al. Low CSF concentration of mitochondrial DNA in preclinical Alzheimer's disease. Annals of Neurology. 2013.