Lewy body disease: a test would detect the disease before the first symptoms

Two studies published in the journal NatureMedicine focused on the early diagnosis of Lewy body disease, the second most common neurodegenerative disease after Alzheimer’s disease. Its symptoms make life difficult for the sick person and those around them. The disease can manifest itself through cognitive disorders (attention disorders, mood swings, loss of cognitive abilities, etc.), unpredictable changes in concentration or wakefulness, hallucinations, motor disorders and sleep disorders. Lewy body disease is caused by abnormal deposits of a protein called alpha-synuclein that form inside brain cells. These deposits are called Lewy bodies. They are the ones that damage nerve cells and trigger the characteristic symptoms of the disease.

Decreased sense of smell, a harbinger of the disease

Until very recently, it was impossible to know for sure whether a person with movement or cognitive impairment had Lewy bodies in the brain before death. Only the examination of his brain after death made it possible to verify this. But now, it is possible to detect Lewy bodies thanks to the analysis of cerebrospinal fluid. The studies published in NatureMedicine completed the work of a large study conducted on more than 1100 people with no cognitive or motor symptoms at the start of the study. Analysis of their cerebrospinal fluid revealed that 10% of them had Lewy bodies in their brains. This means that Lewy body disease can be detected long before the first symptoms appear.

“Even though the participants had no cognitive or neurological impairment at the start of the study, we noticed that those who had Lewy bodies in their brains saw their cognitive functions decline significantly over time. These people also developed Parkinson’s disease or Lewy body dementia in the years that followed.” said Professor Oskar Hansson, professor of neurology at Lund University and co-author of the two studies.

But that’s not all. These studies have also shown that the presence of Lewy bodies in the brain is associated with a reduced sense of smell, long before the appearance of the first symptoms of the disease. According to the researchers, the sense of smell of these patients deteriorates as the disease progresses. “This link is so obvious that it would be legitimate to test the sense of smell of people over the age of 60 before carrying out a cerebrospinal fluid analysis for those who want to know if they have Lewy body disease at an early stage.”, explained Oskar Hansson.

Amyloid plaques + Lewy bodies = rapid disease progression

Several drugs targeting Lewy bodies are currently being studied to slow the progression of the disease. These drugs are likely to be more effective if given at an early stage of the disease. “People without symptoms of the disease who complain of a decrease in their sense of smell and who have tested positive for Lewy bodies could enter clinical trials aimed at developing new drugs capable of slowing the progression of Lewy body disease.”, said Oskar Hansson.

Another important finding revealed by these two studies: people who, in addition to having Lewy bodies, have amyloid plaques and tau protein in their brains are more likely to suffer from a rapidly progressive Lewy body disease. This suggests that these different changes in the brain interact and constitute a decisive element in the estimation of the patient’s prognosis.