Dementia vs. Alzheimer’s: What’s the difference?

Dementia and Alzheimer’s both affect the memory and often they are used interchangeably but there are important distinctions between the two. While people often assume they have the same causes and symptoms, the two overlap in more of a Venn Diagram than as the same diagnosis. There are many types of dementia and not all of them are caused by Alzheimer’s though dementia is often caused by Alzheimer’s.

What is dementia?

                While somewhere between 60-80% of dementia cases are caused by Alzheimer’s, that’s not the only thing that causes it. In fact, dementia is simply a general term to describe the loss of memory, language, problem-solving, and other skills that interfere with someone’s daily life. Dementia is simply an umbrella term for the symptoms caused by abnormal brain changes. While the fist things one might notice are a decline in a loved one’s cognitive abilities, dementia often worsens and begins to affect the person’s behavior, feelings, and even their relationships.

What is Alzheimer’s?

                Until fairly recently people assumed that Alzheimer’s was just a part of aging. The good news is that it isn’t, but on the other side of the coin, aging is the greatest known risk factor at this time with the majority of people diagnosed with Alzheimer’s being 65 or older. Alzheimer’s is a degenerative disease that begins mildly and eventually leaves the patient unable to carry on conversations or even respond to their environment. Currently there is no known cause and no known cure, although scientists are working to determine the role that the buildup of plaque on a patient’s neurons play in Alzheimer’s cases. While there is no cure there is a treatment called Aduhelm that has shown promising results in breaking down the plaque in the brain to help reduce cognitive decline in those in the early stages of Alzheimer’s.

What are the other causes of dementia?

                We know that somewhere between 60 and 80% of dementia cases are attributed to Alzheimer’s, but what about the rest of the cases?

                The second most common cause of dementia is blocked or reduced blood flow to the brain. This is called vascular dementia and accounts for somewhere between 5 and 10% of dementia cases. When the brain can’t get the correct amount of blood to it, it is deprived of nutrients and oxygen. This can be caused by anything that restricts blood flow to the brain, such as strokes or poor vascular health.

                Third is Lewy body dementia and like vascular dementia it accounts for 5 to 10% of dementia cases. Lewy bodies (named for neurologist Frederich Lewy) in the brain are composed of a protein normally found in the brain though scientists are unsure of its normal function. Lewy bodies are also found in those diagnosed with Alzheimer’s and Parkinson’s dementia. Due to the overlap in cognitive and movement symptoms in Parkinson’s, Parkinson’s dementia, and Lewy body dementia may be linked by how the brain processes the protein that makes up the bodies.

                Frontotemporal dementia (FTD) is a type of dementia that doesn’t always begin with memory loss but still makes up between 5 and 10% of dementia cases. While eventually someone with FTD may develop memory loss, more often the symptoms begin with changes in behavior or changes in language skills. While diseases like Alzheimer’s are usually diagnosed in people over 65, FTD is more likely to begin in midlife with some people developing it as early as their 20’s. FTD itself has three subtypes: behavior variant (bvFTD) that affects things like judgment and empathy, primary progressive aphasia (PPA) that affects the language skills, and disturbances of motor movement (such as ALS or progressive supranuclear palsy) that may occur with or without the other two subtypes.

                Covid has brought the idea of comorbidities to the front of everyone’s mind and when two or more conditions are causing cognitive impairment, it is known as mixed dementia. Mixed dementia is under underdiagnosed. Often mixed dementia isn’t diagnosed until after someone has passed away, with 54% of Alzheimer’s patients diagnosed with some sort of coexisting pathology during their autopsies.

                There is still a lot we don’t know about Alzheimer’s and dementia, and that makes it significantly harder to protect ourselves against. But it’s comforting to know that every day scientists are working toward treatments and understanding the causes of the diseased that affect cognitive function. In fact, in early March congress granted $289 million to Alzheimer’s research!