Northern Scotland has one of the highest rates of Huntington’s disease globally, according to new research from the University of Aberdeen.
For the first time in 35 years, scientists have accurately quantified the number of people living 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.
The study, published in Neuroepidemiology, confirmed that northern Scotland has one of the highest rates of Huntington’s disease in the world at 14.5 per 100,000 people, more than five times the estimated worldwide rate of 2.71 per 100,000 people.
Every child of someone affected has a 50:50 chance of inheriting the neurodegenerative gene, which slowly damages the brain, taking away the ability to walk, talk, eat, drink, make decisions and live independently.
On average, every person who has been diagnosed with Huntington’s disease 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.
The research was led by Professor Zosia Miedzybrodzka of the University of Aberdeen and clinical lead for Huntington’s disease at NHS Grampian, alongside Heather Cruickshank, genetic counsellor at NHS Grampian.
Previous studies have mainly looked at the number of people who tested positive for the gene and then estimated the number of relatives at risk using statistical modelling.
In the new study, scientists used family tree clinical records to count how many people have a 50:50 chance of having inherited the condition but have not been tested, amid hopes it will ensure future investment in specialist care.
If rates of Huntington’s disease 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 research.
“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,” Prof Miedzybrodzka said.
“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.”
Ms Cruickshank added: “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.”
Scottish Huntington’s Association chief executive Alistair Haw 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.”
