Scientists have warned Parkinson’s sufferers using a deep brain stimulation device to be cautious about swimming after a group of people reported losing their ability to swim.

According to a study by the American Academy of Neurology, the swimming skills of nine individuals deteriorated once they had deep brain stimulation surgery, despite being good swimmers before and after their Parkinson’s disease diagnosis.

Deep brain stimulation is the main type of surgery used to treat Parkinson’s symptoms which involves implanting a small electrode in the brain connected to a pulse generator that is implanted in the chest like a pacemaker.

A paper published in the Neurology medical journal details three specific cases, including one 69-year-old man who was an experienced swimmer but had to be rescued by a family member after jumping into a lake and almost drowning.

Three of the nine patients switched off their deep brain stimulation device for swimming and found their ability to swim came back immediately, though Parkinson’s disease motor symptoms deteriorated rapidly leading them to switch stimulation on again as soon as possible.

However, researchers say the exact percentage of patients who experience deterioration of swimming abilities is not known.

“Until more research is done to determine why some people with deep brain stimulation can no longer swim, it is crucial that people be told now of the potential risk of drowning and the need for a carefully supervised assessment of their swimming skills before going into deep water,” said author Dr Daniel Waldvogel, from the University of Zurich in Switzerland.

“Swimming is a highly co-ordinated movement that requires complicated arm and leg coordination.

“Exactly how deep brain stimulation is interfering with this ability needs to be determined.”

Katie Goates, communications manager at charity Parkinson’s UK, said: “This study reports on a very small number of people experiencing an effect on their ability to swim following deep brain stimulation.

“We know that reduced co-ordination can be a side effect of deep brain stimulation for Parkinson’s, however we also know that the treatment can work well to control symptoms and many people experience life-changing benefits because of it.

“All current treatments for Parkinson’s have potential side effects and we desperately need better treatments for the 145,000 people living with the condition in the UK.

“Anyone with specific concerns about the side effects of their Parkinson’s treatment should discuss this with their healthcare team.”