Researchers this week announced that the earliest signs of Alzheimer’s disease yet detected have been found in a group of people with a rare inherited form of the disease. Two new studies on the subject were published in the journal Lancet Neurology. The studies were led by doctors from the Banner Alzheimer’s Institute in Arizona, Boston University, and the University of Antioquia in Colombia.

The studies looked at a group of around 5,000 related people in Colombia who could carry a rare mutation of a gene called presenilin 1 (PSEN1). Around 30% of the group had the mutation, which indicates certain early-onset of Alzheimer’s disease.

In one study, researchers performed brain imaging, blood tests, and some cerebrospinal fluid analysis on 44 adults age 18 – 26, 20 of whom had the PSEN1 mutation. Though none of the patients had evidence of cognitive impairment at the time of the study, researchers found differences in the “brain structure and function” between those with the mutation and those without. PSEN1 carriers were found to have more brain activity in the hippocampus and parahippocampus regions of the brain, as well as having higher levels of a protein called amyloid beta in their cerebrospinal fluid.

“These findings suggest that brain changes begin many years before the clinical onset of Alzheimer’s disease, and even before the onset of amyloid plaque deposition,” said Dr. Eric Reiman of the Banner Alzheimer’s Institute. “They raise new questions about the earliest brain changes involved in the predisposition to Alzheimer’s and the extent to which they could be targeted by future prevention therapies.”

The other study tracked amyloid plaque deposits in the brains of 50 people aged 20 – 56. Those patients with the PSEN1 mutation were discovered to have amyloid plaques begin to accumulate as early as their late 20s. According to the study’s authors, the findings will “help set the stage for the evaluation of treatments to prevent familial Alzheimer’s disease, and hopefully aid our understanding of the early stages of late-onset Alzheimer’s disease, which is more widespread.”