A relatively simple skin test could eventually lead to the early diagnosis of Alzheimer’s and Parkinson’s diseases, a new study suggests.

The study — which is to be presented at next month’s meeting of the American Academy of Neurology’s annual meeting in Washington, D.C. — suggests that minimally invasive skin biopsies could detect the presence of abnormal proteins associated with the two most frequently diagnosed degenerative diseases of the brain.

The research could open yet another avenue toward finding less intrusive and relatively inexpensive biomarkers for two neurodegenerative diseases, the scientists said. Other studies, for example, have suggested that eye scans and smell tests could be used to identify Alzheimer’s in its early stages.

“We are confident that [skin tests] will prove a valuable tool for the diagnosis of these diseases,” said Ildefonso Rodriguez-Leyva, who is the study author for a team of scientists at the Central Hospital at the University of San Luis Potosi in Mexico.

Rodriguez-Leyva said researchers wanted to see whether they could find traces of abnormally folded proteins that have been linked to neurodegenerative disease. The team focused on the skin as a potential biomarker for brain disease because both organs share the same embryological origin.

What they found was that the skin samples of test subjects who had Alzheimer’s also had significantly higher levels of tau protein, which has been implicated in the disease. A similar finding occurred in subjects with Parkinson’s: Their skin biopsies contained significantly higher levels of alpha-synuclein, which is indicative of Parkinson’s, according to an abstract of the study.

Researchers have devoted more attention to finding ways to detect Alzheimer’s disease and other age-related ailments sooner and with less expensive technology as the United States and other countries brace for a demographic shift toward older populations. A recent report on the financial impact of Alzheimer’s in the United States warned that the cost could top $1 trillion per year by 2050, with much of that borne by the federal government.

The San Luis Potosi University study focused on 65 subjects. The team obtained skin biopsies from behind the ears of 20 people with Alzheimer’s disease, 16 with Parkinson’s disease, 17 who had developed dementia from other causes, and 12 healthy people as control subjects. The skin samples can be obtained easily and with less pain than at other sites and do not leave scars, Rodriguez-Leyva said.

The scientists examined the samples for antibodies related to the abnormal proteins. Those with Alzheimer’s had levels of tau protein that were seven times higher than those who were healthy; those with Parkinson’s had eight times the level of the alpha-synuclein protein, the researchers said.

In e-mails, Rodriguez-Leyva acknowledged that the sample size was small but not unusually so for such preliminary studies.

“It is only the beginning,” he wrote. “We need to make a larger study and to get our results replicated by other researchers to give validity to the test.” But he also suggested that such a test could be developed in two years or so.

According to the American Parkinson Disease Association, more than 1 million Americans suffer from the affliction, with about 60,000 new diagnoses a year. The disease, which generally strikes people in their 50s and later, causes the deterioration of a person’s motor skills and also can cause anxiety, depression and other symptoms.

Alzheimer’s is the leading cause of dementia, affecting more than 5 million people, the Alzheimer’s Association said. The disease is incurable and progressive, leading ultimately to death. The number of cases is expected to increase to 13.5 million by 2050.

The latest findings on skin tests will be presented at the American Academy of Neurology’s conference April 18-25.