A brain disease closely linked to dementia may begin much earlier than many people realize.
Researchers in Finland found signs of Lewy body disease in some people over age 50 who had never been diagnosed with the condition.
The study was carried out by researchers from the University of Helsinki and Tampere University. The findings were published in the medical journal Annals of Neurology.
Lewy body disease is one of the most common causes of dementia after Alzheimer’s disease. It is linked to unusual clumps of a protein called alpha-synuclein that collect inside nerve cells in the brain.
These clumps are known as Lewy bodies. As they build up, they can interfere with brain areas involved in thinking, memory, movement, sleep, behavior, and emotions.
Lewy body disease is also closely connected with Parkinson’s disease. Both conditions involve abnormal alpha-synuclein, although the symptoms and the way the disease develops can differ from person to person.
One major problem is that Lewy body disease can be difficult to recognize. Symptoms may include memory and thinking problems, changes in attention, visual hallucinations, sleep problems, and movement difficulties similar to those seen in Parkinson’s disease.
These problems usually become noticeable only after changes have already been developing in the brain for years. Scientists therefore want to understand what happens during the much earlier, silent stage of the disease.
For the Finnish study, researchers examined brain tissue collected during forensic autopsies. The study included about 600 people between the ages of 16 and 95 who had died outside hospitals and had not been diagnosed with a neurological disease.
This approach allowed the team to look for early brain changes in people who had shown no known signs of Lewy body disease during life. It also provided a rare opportunity to study people across a very wide age range.
The researchers found evidence of Lewy-related brain changes in about 9% of people older than 50. These people had not been diagnosed with Parkinson’s disease or Lewy body dementia before they died.
The finding suggests that abnormal protein deposits may sometimes begin forming during middle age, long before symptoms become obvious. This challenges the idea that Lewy body disease is mainly a condition that starts late in old age.
However, finding Lewy bodies in brain tissue does not mean that every person would eventually have developed dementia or Parkinson’s disease. Some early brain changes may never progress far enough to cause noticeable symptoms during a person’s lifetime.
Associate Professor Liisa Myllykangas, who led the research, said the early findings need to be confirmed in further studies. Understanding how often these silent changes progress into disease will be especially important.
If scientists can identify the earliest stages of Lewy body disease, it could eventually change how the condition is diagnosed and treated. Researchers are increasingly interested in finding brain diseases before major nerve-cell damage occurs, when future treatments might have a better chance of working.
At present, there is no routine screening test that can tell healthy middle-aged people whether Lewy body disease has silently begun. Diagnosis is generally based on symptoms, medical history, examinations, and tests used to rule out or identify related conditions.
The Finnish findings provide another clue about the long period that may exist between the first biological changes in the brain and the appearance of dementia. More research could help scientists develop blood tests, brain scans, or other tools capable of detecting these changes earlier.
Such advances could eventually give doctors a much larger window for treatment. For now, the study adds to growing evidence that some diseases associated with dementia may begin quietly many years before memory, thinking, or movement problems become clear.
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