Sleep disorder linked to Parkinson’s and dementia

Acting out violent dreams may be a sign of future illness, study says
Paul Taylor

Globe Life - People who suffer from a bizarre sleep disorder, in which they act out violent dreams with nocturnal kicks and punches, appear to be at increased risk of developing Parkinson’s disease or dementia later in life.

In fact, a recent study suggests the sleep disorder may precede these neurological illnesses by as many as 50 years.

“Our paper implies [the disease progression] is an extremely slow process in some people,” said the lead researcher, Bradley Boeve of the Mayo Clinic in Rochester, Minn.

The unusual behaviour takes place during rapid-eye-movement (REM) sleep, when dreams tend to occur. Most people experience a form of temporary muscle paralysis during this sleep phase to prevent them from acting out their dreams. But those with REM-sleep behaviour disorder, or RBD for short, are free to move. And their dreams often have violent themes. So they kick and punch and sometimes fall out of bed – with potentially painful consequences.

“They are usually being attacked or chased by someone or something [in their dreams],” said Dr. Boeve. “They try to defend themselves and flail their limbs, but in so doing they can accidentally hurt themselves or their bed partners.”

The disorder tends to afflict more men than woman. “Wives will say, ‘I remember on my wedding night, I got punched in the arm’,” noted Dr. Boeve. The episodes may occur as frequently as several times a night, or be limited to just a few times a month.

U.S. researchers first began to record cases of this sleep disorder about two decades ago. Initially, the medical community didn’t pay much attention to RBD. But over the years, an alarming number of these patients have come down with one of three related neurological conditions: Parkinson’s disease, in which muscle control is gradually lost; dementia with Lewy bodies (abnormal proteins inside nerve cells); or multiple system atrophy.

These cases prompted researchers at the Mayo Clinic to dig deep into their files to pinpoint patients who had RBD for at least 15 years before being diagnosed with one of the degenerative brain disorders. In total they identified 27 patients who fit the bill. On further examination, they learned the time between the start of the sleep problems and the emergence of symptoms of a neurological illness ranged up to 50 years, with an average span of 25 years.

The Mayo Clinic researchers published their findings in the journal Neurology.

So what’s going on with these patients? It’s possible that the sleep disturbance is simply an early manifestation of the other conditions, said Dr. Boeve. In other words, the sleep problems show up first and eventually other symptoms become apparent as the disease state slowly progresses to different parts of the brain.

If that is indeed the case, then the sleep disorder could help alert doctors to the fact that a more serious illness could be on the way. The problem is that researchers can’t yet say which RBD patients will go on to develop Parkinson’s disease or the other related disorders. And some patients may never suffer from anything more than troubled sleep.

Even so, Dr. Boeve said researchers may some day develop treatments that can slow or even prevent the progression of these diseases. And having an indication of who is most at risk means treatment could be given at an early stage of the disease when there is a greater chance of it being effective.