For patients with Parkinson disease (PD), cognitive decline can be one of the most debilitating symptoms of the condition. As many as 80 per cent of people with PD experience some form of cognitive impairment, with up to a quarter of patients presenting symptoms of memory loss or impairment at diagnosis. In the Centre for Applied Neurogenetics at the Djavad Mowafaghian Centre for Brain Health, researchers performing genetic sequencing have found a biomarker that may enable physicians to predict whether an individual is at increased risk for dementia.

According to Dr. Ilaria Guella, a Research Associate in neurogenetics and a member of Dr. Matt Farrer’s research team, this discovery is significant.

“Using massively parallel sequencing, we have characterized the entire SNCA gene, which codes for the  alpha-synuclein protein,” says Dr. Guella. “We found the exact genetic variation that identifies which patients with PD are most likely to develop dementia.”

Discovering a biomarker for dementia in PD gives researchers a target for drug development, and will be helpful in designing clinical trials aimed at modifying the disease course. Knowing which patients have a heightened risk of dementia will enable physicians to customize individual treatment plans to ease the burden of the disease on the patient and their families.

“Cognitive decline and dementia is a major problem in PD, albeit under recognized. Defining the major genetic influence for motor and cognitive problems is a significant step in prediction and prevention for this syndrome,” says Dr. Farrer. “Our thanks goes out to everyone that took part and for their many years of consistent effort”

“SNCA remains the only gene unequivocally associated with disease susceptibility, progression, and pathology,” says Dr. Guella. “We have demonstrated a clear genetic predictor of cognitive decline, and our hope, moving forward, is to use the SNCA data we have – on thousands of patients – to inform research on PD disease progression, protein expression in the brain, and protein clumping in the brains of patients with PD.”

Read more: α-synuclein genetic variability: A biomarker for dementia in Parkinson disease