Scotland has one of the highest Huntington’s disease rates, research finds

Northern Scotland has one of the world’s highest Huntington’s disease rates, more than five times the estimated global average, new research shows.

For the first time in 35 years, scientists have accurately quantified the number of people in the region carrying the gene that causes the condition.

Using NHS family-based records, researchers identified more than 160 adults living in Grampian, Highland, Orkney, Shetland and the Western Isles who have the gene but remain untested.

Researchers believe the actual figure is likely higher as not everyone with symptoms seeks a formal diagnosis.

Professor Zosia Miedzybrodzka of the University of Aberdeen and clinical lead for Huntington’s disease at NHS Grampian said: “Previous work looked at how many people in the area have been tested for Huntington’s disease, that is, people diagnosed with Huntington’s disease signs and those with a gene alteration that will develop the condition in later life.”

“However, no-one has properly counted just how many people who haven’t been tested yet must have the gene.

“It is crucial that we know this, and that it is accurate, so that health boards can properly plan for care and for treatments when they become available in the future.

“A 2022 Scottish Government report underestimated Huntington’s disease rates and did not account for numbers of people at risk in a way that our data has.”

Huntington’s disease is a neurodegenerative condition that slowly damages the brain, affecting movement, speech, swallowing and decision-making, and can remove the ability to live independently.

Every child of someone affected has a 50:50 chance of inheriting the gene.

The study confirmed that northern Scotland has a rate of 14.5 per 100,000 people, compared with the estimated worldwide rate of 2.71 per 100,000 people.

On average, every person diagnosed will have at least another 2.2 relatives who have the gene, meaning there are hundreds of people in northern Scotland who could be considered for effective treatments in the future, researchers said.

If rates across Scotland are similar to the north, around 800 people are manifesting signs of the condition, and almost 2,500 have the gene, according to the research.

Heather Cruickshank, genetic counsellor at NHS Grampian, said: “In 1989, when scientists previously studied this, testing was not possible, fewer people had a diagnosis, families were larger.

“Despite high rates of testing, most people at risk of developing Huntington’s disease in Scotland have not had a test. There is a massive worldwide effort seeking treatments for Huntington’s disease.”

“Services need to plan to treat these as-yet-uncounted people, as well as those currently diagnosed. Regional variations in rates will become more important, including genetic counselling and testing, management, and treatment delivery.

“Better knowledge of the numbers of people who could benefit will encourage investment into drug discovery.

“Having a test remains a free choice for people from Huntington’s disease families and our research means that care can be planned for all those at risk, without people who don’t want a test having one.”

Alistair Haw, chief executive of Scottish Huntington’s Association, said: “Earlier this term a Scottish Parliament motion calling for an expansion of specialist Huntington’s disease services in light of rising cases became the most supported motion in the history of devolution.

“This latest study further strengthens the case for immediate action to expand specialist services for families impacted by Huntington’s.

“Huntington’s disease is a hugely complex, widely misunderstood and extremely difficult to manage condition.

“Specialist services are not some ‘nice to have’ optional extra but an absolute necessity to prevent patients reaching crisis point and presenting to acute emergency statutory services.”