Dementia vs Alzheimer's: What's the Difference?

It's one of the most common mix-ups in this whole area, and an understandable one. If you've just heard the word "dementia" attached to someone you love, or you're trying to make sense of a diagnosis, it helps to get this one distinction clear early, because a lot of what follows depends on it.

Dementia is the umbrella, not the disease

Dementia isn't a specific illness. It's a general term for a set of symptoms, memory problems, difficulty finding words, trouble with planning and decision-making, changes in mood or behaviour, that become severe enough to interfere with everyday life. Those symptoms have to be caused by something. Dementia is the name for the symptoms; the underlying disease is what's actually causing them.

Where Alzheimer's fits in

Alzheimer's disease is a specific brain disease, and it's the most common cause of dementia by far, responsible for around 60% of dementia diagnoses in the UK. It's caused by a build-up of proteins in the brain that gradually damage the way brain cells communicate with each other.

So every case of Alzheimer's is dementia, but not every case of dementia is Alzheimer's. Think of dementia as the category, and Alzheimer's as the single largest thing that falls inside it.

What else can cause dementia

• Vascular dementia, the second most common cause, caused by reduced blood flow to the brain, often following a stroke or a series of smaller, unnoticed ones. Read our full guide on vascular dementia →
• Lewy body dementia, caused by abnormal protein deposits called Lewy bodies, often involving vivid hallucinations and fluctuating alertness. Read our full guide on Lewy body dementia →
• Frontotemporal dementia, which affects personality and behaviour before memory, and is often mistaken for a mid-life crisis or mental health problem before anyone thinks of dementia. Read our full guide on frontotemporal dementia →
• Mixed dementia, where more than one of these processes is happening at once, most commonly Alzheimer's alongside vascular disease.

Why the distinction actually matters

This isn't just semantics. Different causes of dementia can have different early warning signs, different typical patterns of progression (gradual versus stepwise, for example), and sometimes real, practical differences in treatment, including which medications are safe to use. Knowing the specific cause, where possible, helps a family understand what's likely to come and plan around it, rather than treating every dementia diagnosis as identical.

One more thing worth knowing

Not every memory or thinking problem is dementia. Medication side effects, sleep problems, depression, thyroid issues, vitamin deficiencies, and infections can all cause similar symptoms, and some of these are entirely treatable. Mild cognitive impairment (MCI) is also a distinct, separate thing from dementia, and doesn't automatically progress to it. This is exactly why a proper assessment matters when symptoms first appear, rather than assuming the worst or dismissing early changes.

A word from The Care Compass

If you're newly navigating any of this, the terminology alone can feel like its own maze. You don't need to become an expert overnight. Getting this one distinction, dementia the umbrella, Alzheimer's the most common disease underneath it, straight is often the first thing that makes the rest of it easier to follow.

This article is for general guidance only and does not constitute medical advice. For any concerns about symptoms or a diagnosis, speak to a GP or specialist directly.

You don’t have to navigate it alone.