Mixed Dementia: More Common Than Previously Thought, Especially in Older Adults

For many years, dementia research and diagnosis focused on singular forms of the condition—Alzheimer’s disease, vascular dementia, Lewy body dementia, and frontotemporal dementia. However, recent studies suggest that mixed dementia—where a person has two or more types of dementia simultaneously—is far more prevalent than previously believed, particularly among older adults.

What Is Mixed Dementia?

Mixed dementia occurs when changes associated with more than one type of dementia are present in the brain. The most common combination is Alzheimer’s disease and vascular dementia, though some people may also have features of Lewy body dementia or other forms. This overlapping pathology can make symptoms more complex and diagnosis more challenging.

Research has shown that mixed dementia is under-recognised, partly because medical professionals often focus on identifying the most prominent form of dementia rather than considering multiple coexisting conditions.

Why Is Mixed Dementia More Common in Older Adults?

Age is the single biggest risk factor for dementia. As people live longer, the likelihood of developing more than one type of dementia increases. Several factors contribute to this:

• Overlapping Risk Factors – Conditions such as high blood pressure, diabetes, and heart disease increase the risk of both Alzheimer’s disease and vascular dementia. Older adults who have lived with these conditions for many years are at greater risk of developing mixed dementia.
• Brain Ageing – As the brain ages, multiple types of damage can occur. For example, plaques and tangles characteristic of Alzheimer’s disease may develop alongside blood vessel damage seen in vascular dementia.
• Underdiagnosis in Life – Many cases of mixed dementia are only confirmed through post-mortem studies. During life, clinicians may diagnose a single type of dementia because symptoms of multiple types often overlap.

Symptoms of Mixed Dementia

The symptoms of mixed dementia vary depending on which types are present and how they interact. Common symptoms include:

• Memory loss – A hallmark of Alzheimer’s disease, but also seen in vascular dementia.
• Confusion and disorientation – Often worsened by vascular dementia’s impact on brain function.
• Difficulty with problem-solving and decision-making – Can be linked to both Alzheimer’s disease and vascular dementia.
• Movement difficulties – More likely when Lewy body dementia is involved.
• Fluctuations in cognition – Seen in dementia with Lewy bodies but also common in advanced Alzheimer’s and vascular dementia.

Because mixed dementia includes elements of different conditions, its progression can be unpredictable. Some people may have sudden declines linked to vascular dementia, while others experience a more gradual progression associated with Alzheimer’s disease.

Why Recognising Mixed Dementia Matters

Understanding that mixed dementia is common has important implications for diagnosis, treatment, and care:

• Improved Diagnosis – Recognising that a person may have more than one type of dementia helps healthcare professionals tailor treatment and support.
• More Effective Treatment Plans – Certain medications may be more or less effective depending on the mix of dementia types present. For example, cholinesterase inhibitors used for Alzheimer’s and Lewy body dementia may not help as much with vascular dementia symptoms.
• Better Support for Carers – Understanding the complexities of mixed dementia can help carers anticipate changes and manage symptoms more effectively.

The Future of Research and Diagnosis

Researchers are increasingly studying mixed dementia to develop better diagnostic tools. Advances in brain imaging, biomarker testing, and genetic research may help identify mixed dementia earlier in life. Greater awareness among medical professionals and the public can also lead to more comprehensive care approaches.

For now, the key takeaway is that mixed dementia is likely more common than we once thought, particularly in older adults. Recognising this can help families and professionals better understand the needs of those living with dementia and provide the best possible support.

Sources:

• Alzheimer’s Society UK. (2024). Mixed dementia: What you need to know.
• National Institute on Aging. (2023). What is mixed dementia?
• Livingston, G., et al. (2020). Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. The Lancet.
• Love, S. et al. (2019). Mixed dementia: The importance of recognising multiple pathologies. Brain, 142(3), 525–532.
• Vascular Dementia Society UK. (2023). Understanding vascular dementia and its overlap with other dementias.