The gene that causes the devastating brain disorder, Huntington’s disease (HD) could affect more than 10 times as many people than previously thought, according to new research.

Scientists from the University of Aberdeen, the University of British Columbia and the Coriell Institute for Medical Research found that as many as 1-400 people could be at risk of developing the condition. Previously it was thought HD affected around 1-5000 of the population.

The disease is an incurable genetic condition that usually starts between the ages of 35 and 45 years. It begins with personality changes that can make those diagnosed aggressive, anxious and depressed. The disease progresses slowly, with changes to muscle control that slowly erodes mobility and the ability to talk. As it progress those affected will need 24 hour care. It is also hereditary with each child of those diagnosed at 50% risk of developing the disease.

The study, published last month by the American Academy of Neurology, is the first to reveal just how common the genetic mutation that causes Huntington’s disease is in the general population.

The test for HD is relatively straight forward with people registering a certain amount of the mutated gene definitely developing the disease.

However, until now it has remained unclear how many people in the general population have enough of the gene that causes Huntington’s disease, and how many of them are at risk of developing it.

“It has been a difficult question to answer, since no one has ever examined the gene repeats in large numbers of people outside the clinic,” says Chris Kay from the University of British Columbia, lead author on the manuscript. “We had estimates based on how many patients we see, but our study in Canada, United States of America and Scotland found far more mutations than expected.”

People with less incidents of the mutated gene usually develop HD over the age of 60. However, the new results suggest that many people with the mutation may never actually develop the disease, but may be passing on a more serious risk of their children developing full blown HD.

The Scottish Huntington’s Association is the only charity in the country supporting families living with HD

Its chief executive, John Eden said:

“These results may mean we are seriously underestimating the number of elderly patients with the condition. Their symptoms may not be clearly recognised as HD, meaning there could be a whole generation of their children potential at risk and they do not even realise it.

Co-author of the study was Professor Zosia Miedzybrodzka from the University of Aberdeen.

“Recognising the disease in more people who actually have problems from it should improve their medical care.”

The SHA is currently rolling out a national HD care framework which will standardise standards of care for patients across the country for the first time.

“This research shows that the incidents of HD we are currently seeing might only the tip of the ice berg. This could have serious implications for care funding for the condition and I would urge the Scottish Government to look closely at the results of this study when planning future provision for HD care.”

The study was funded by the Canadian Institutes of Health Research with the assistance of the Coriell Institute for Medical Research and the NHS Grampian Huntington’s disease endowments research fund.