Introduction 

Dementia is an umbrella term for a collection of symptoms that are associated with a progressive decline in normal brain functioning, which means that the severity of the disorder gets worse with time. Lewy body dementia is the third most common form of dementia apart from Alzheimer’s disease or vascular dementia.¹ Dementia usually affects older people aged 60 and above, but this is not a normal process in ageing. Common symptoms of dementia include memory loss, hallucinations and difficulty in thinking or other cognitive abilities. This affects an individual’s capability to support themselves and may lead to a loss of independence in daily activities. This article will illustrate how Lewy body dementia affects cognition and thinking and the impact on the quality of life in affected individuals.

Lewy body dementia

Lewy body dementia is a neurodegenerative disorder identified by the presence of Lewy bodies in the brain. Lewy bodies are named after the neurologist Friedrich Lewy, who discovered these protein deposits. ² They are clumps of protein (made of ubiquitin and alpha-synuclein) that build up in the brain's nerve cells (neurons) and damage normal brain functioning. ² Neurons act as messengers for the communication of signals across different brain regions, so these Lewy bodies abnormally accumulate in neurons and disrupt the messaging network of the brain. They are commonly found in affected individuals' cerebral cortex, basal ganglia, and brainstem regions.¹ Further research is required to determine the exact cause behind the appearance of these Lewy bodies. 

A deficiency in acetylcholine in the brain's temporal and parietal cortex regions leads to visual hallucinations.¹ Acetylcholine is a neurotransmitter (a chemical that aids in the communication of signals from the brain to the body) responsible for memory, attention, learning, arousal and involuntary muscle movements, and rapid eye movement (REM) sleep. Visual hallucination symptoms are present in up to 80% of all cases of Lewy body dementia (Alzheimers.gov). Deficiencies in another neurotransmitter, called dopamine, have also been detected in some cases of Lewy body dementia. Dopamine is responsible for the regulation of motivation, memory, attention, mood and many other functions. Low dopamine levels lead to memory loss, apathy, depression, fatigue, difficulties in attention, sleep and other cognitive abilities. Low dopamine is also a significant feature of Parkinson’s disease dementia, which is classified as a subtype of dementia with Lewy bodies. Usually, dementia with Lewy bodies is characterised by the initial appearance of Lewy bodies in the cerebral cortex and brainstem. In Parkinson’s dementia, Lewy bodies first appear in the brainstem and then spread to the cerebral cortex in later stages. Symptoms of Lewy body dementia can resemble those of Alzheimer’s or Parkinson’s disease, which demands careful diagnosis for the appropriate treatment or medication to relieve the symptoms.

Symptoms

Lewy bodies lead to the development of the following symptoms:

• Visual hallucinations
• Cognitive difficulties such as fluctuating attention or alertness, memory loss, visual-spatial problems
• Trouble sleeping, such as REM sleep behaviour disorder (RBD)
• Parkinsonism (tremors, rigidity or stiffness, and slowed movements or bradykinesia)
• Depression, apathy or loss of motivation
• Dysautonomia or improper regulation of normal body functions like blood pressure, heart rate, digestion, and sweating.

Cognitive impairments 

Cognitive impairments in Lewy body dementia impact memory, attention, and executive functions (planning, reasoning, problem-solving, multitasking). In progressive dementias, memory and executive functions are mainly impacted.¹ Visual-spatial abilities are also affected, such as perception of depth, the orientation of objects in space, and the processing of visual information due to damage to the occipital and parietal lobes of the brain.³ Thinking and Behavioral Changes

Cognitive impairments can induce changes in one’s mood, behaviour and thinking. Visual hallucinations occur due to decreased levels of acetylcholine in the temporal and parietal cortex of the brain, and delusions occur due to the up-regulation of the M1 muscarinic receptor ¹. The M1 muscarinic receptor responds to acetylcholine and aids in the learning and memory processes of the brain.⁴ Visual hallucinations and delusions can lead to confusion and fluctuations in mood, such as anxiety, depression, and apathy. In severe cases, one may even start to show aggressive behaviour. Those with Lewy body dementia commonly experience REM sleep behaviour disorder or RBD, wherein flailing, punching, yelling or speaking during their sleep is a recurrent event. They may also experience insomnia, excessive daytime drowsiness, changes in their sleeping patterns, and restless leg syndrome. 

A key difference to note is that in dementia with Lewy bodies, difficulties in thinking, visual hallucinations, and fluctuations in attention and alertness appear earlier than symptoms of Parkinsonism. However, in Parkinson’s disease dementia, parkinsonism appears earlier, and not everyone develops dementia. 

Frequently asked questions 

What daily activities are most affected by Lewy body dementia (LBD)?

Lewy body dementia impacts memory, attention, and executive functions (planning, reasoning, problem-solving, and multitasking). Therefore, preparing meals, eating, general household tasks and personal hygiene are all impacted.

Is there a treatment for the symptoms of LBD?

Unfortunately, there is no cure for LBD and most of the options available focus on the management of symptoms. However, it is of utmost importance to seek professional help from a doctor to diagnose and manage the disorder appropriately. 

Are hallucinations a common cognitive symptom of LBD?

Yes, it is quite a common symptom that can display itself from the onset of the condition.

How does LBD affect sleep?

Those with Lewy body dementia commonly experience REM sleep behaviour disorder or RBD, wherein flailing, punching, yelling or speaking during their sleep is a recurrent event. They may also experience insomnia, excessive daytime drowsiness, changes in their sleeping patterns, and restless leg syndrome. 

Summary 

Lewy body dementia is the third most common form of dementia in the world after Alzheimer’s disease and vascular dementia. It can be subdivided into dementia with Lewy bodies and Parkinson’s disease dementia based on the order of appearance of symptoms. Lewy body dementia occurs due to an accumulation of Lewy body deposits in the neurons of the brain, which disrupt normal brain signalling for cognition and behaviour. A deficiency in the neurotransmitter acetylcholine is responsible for the symptoms of Lewy body dementia, but an extensive study is required to find the exact cause of the accumulation of these Lewy bodies. Common symptoms include visual hallucinations, parkinsonism, fluctuation in attention and alertness, and REM sleep behaviour disorder (RBD). Cognitive impairments affect memory, attention, and executive functions like planning, reasoning, problem-solving and multi-tasking. Changes in thinking, mood, and behaviour include visual hallucinations, delusions, anxiety, depression, apathy, RBD, and even aggressive behaviour. Due to the similarities in symptoms of dementia with Lewy bodies and Parkinson’s disease dementia, it is of utmost importance to seek professional help from a doctor for the appropriate diagnosis and management of the disorder.