Lewy body dementia – How it Affects the Sensory System

Lewy body dementia affects many parts of the body and causes a wide variety of symptoms. The central symptom is a decline in cognition, such as memory, thinking, or decision making. A change in movement abilities is also a core feature of both dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD). Sleep difficulties and changes in autonomic function—such as serious constipation and/or fainting—are also common.

But did you know that LBD also affects the senses and the way we perceive the people and objects around us?

Vision and LBD

Vision and our visual experience can be affected in multiple ways in LBD. One of the most common is the experience of visual hallucinations, or perceiving that you can “see” something or someone that is not present. In DLB, hallucinations tend to be well formed and detailed. Fortunately, the visual hallucinations frequently associated with DLB are not usually distressing to the person with DLB or to others around them, and in fact they may even be comforting. For example, a person may experience “seeing” a favorite pet from earlier in their life.

But vision and visual perception may also be affected by LBD in other ways.

  • People with LBD may have difficulty with color vision discrimination (seeing different hues)
  • Changes in cognition can also affect our visual abilities
    • It may become difficult to recognize objects, particularly in visually “busy” areas such as pantries or medicine cabinets
    • It may become difficult to locate where objects are with respect to the body or to other objects
    • Driving may become more difficult or even unsafe

Researchers have recently begun taking advantage of an interesting quirk of human nature called pareidolia to study changes in visual abilities in LBD. Pareidolia is the word for the tendency to impart extra meaning onto visual scenes, such as seeing “faces” in the fronts of cars. In “busy” visual scenes, people with LBD often report these images as being actually present rather than as fleeting perceptions. Researchers have suggested that a pareidolia test may someday be used to identify people in the early stages of LBD.

To learn more about vision and LBD you can watch the recording of our Community Webinar on this topic and for tips on managing visual changes in LBD you can download our booklet on visual function in Lewy body dementia.

Smell and LBD

Surprisingly, smell may be one of the first senses affected by LBD. Smell and cognition are closely linked; you can likely think of a time when a particular smell such as a childhood favorite food or a familiar perfume practically transported you back to a strong memory from earlier in your life. Loss of the ability to detect smells or tell smells apart may be a very early indicator that Lewy bodies are present in the brain.

Hearing and LBD

Doctors have considered untreated hearing loss a major risk factor for dementia since at least 2017, and more recently it has been suggested that it is the single largest modifiable risk factor for dementia around the world. Hearing loss is particularly common in Lewy body dementia—people with Lewy bodies have double the risk of hearing loss compared to others of the same age, according to a recent study from Newcastle University in the United Kingdom.

So does that mean that treating hearing loss could prevent dementia? Treating hearing loss is unlikely to reverse or fully prevent the brain diseases that cause dementia, but it might slow cognitive decline in people who are at risk of dementia. This was recently tested in a large clinical trial. People at high risk of dementia and people with average risk were randomly assigned to either a hearing intervention (hearing aids and counseling with an audiologist) or a general health education intervention for comparison. Their cognition was then studied every six months for three years. Among people at high risk for developing dementia, the hearing intervention slowed their cognitive decline by nearly 50%.

What does this mean for me?

Changes in the senses are common in LBD. If you have experienced changes in your senses, be sure to tell your doctors. If you have LBD, let the healthcare professionals who take care of your senses know, such as your eye doctor or audiologist, as this information may inform the way they diagnose and/or treat any sensory concerns you have. Also, whether you currently have LBD or not, if you have concerns about your hearing, do not delay in seeking an evaluation and treatment if needed. It may be one of the single most important things you can do to protect your cognition later in life.




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