The word dementia is often used as if it were a diagnosis. In fact, dementia describes a situation in which changes in thinking, memory, language, or behaviour affect daily life and independence. Therefore, it describes the consequences of a disease affecting brain function, rather than the disease itself.

Alzheimer’s disease is one of many diseases that can cause dementia.

This difference is important because understanding what’s causing someone’s symptoms can make a real difference, not just medically, but emotionally, for people and their whānau. In clinic, this distinction comes up all the time. People have often been told they have “dementia” without being given a clear explanation of what’s causing it, or what that means for the future.

Dementia and Alzheimer’s disease are not the same thing

Dementia isn’t a disease in itself. It’s a description of what’s happening when cognitive changes start to interfere with everyday life.

Alzheimer’s disease is the most common cause of dementia, both in older people and in those diagnosed at a younger age. It’s associated with specific changes in the brain, including the build-up of abnormal proteins called amyloid and tau, which interfere with brain function over time.

One of the challenges with Alzheimer’s is that it doesn’t always look the same in everyone. While many people think of memory loss first, Alzheimer’s can also initially affect language, visual processing, or problem-solving, and can cause subtle changes in behaviour, such as loss of motivation. That variability can make diagnosis harder and, at times, slower than people would like.

Why early and accurate diagnosis matters

People come for assessment for different reasons. Some notice memory or concentration problems and wonder whether stress, anxiety or depression might be the cause. Others experience changes that slowly worsen over months or years, but it isn’t yet clear what’s behind them. Less commonly, people present with unusual or confusing symptoms that don’t fit a familiar pattern.

In all of these situations, uncertainty can be deeply unsettling. Many people describe a period of self-doubt and anxiety, particularly when difficulties begin to affect work or relationships. This, in turn, can further affect their function in a negative spiral, whatever the cause turns out to be. For many, having a clear diagnosis lifts a heavy burden of self-blame and worry, even when the news itself is difficult.

Knowing what’s happening helps people stop questioning themselves, plan ahead, and access the right support. It can also reduce the need for repeated testing and investigations, which, in themselves, can be exhausting and distressing. Everybody experiences minor slips in their thinking – like forgetting a word or someone’s name – from time to time. We suggest seeking a medical review, which usually begins with an appointment with your GP, if you’re experiencing more persistent symptoms that are interfering with your daily function.

What assessment involves

Assessment for cognitive change isn’t based on a single test or scan. It involves listening, observing, and gathering information over time. The cornerstone of assessment remains the clinical history – what changes has a person noticed, how have they progressed across time, and how is their everyday life going. It’s also important to find out about other things that can also affect thinking, such as changes in mood or sleep.

Input from whānau members, friends or others who know the person well is also crucial, as changes aren’t always obvious to the person experiencing them. This is usually accompanied by a physical examination to look for evidence of processes that might be affecting the nervous system (this is often fairly normal in people with Alzheimer’s disease, but can provide important clues in conditions such as dementia with Lewy bodies or frontotemporal dementias).

Cognitive tests we use in the clinical setting provide screening assessments of different areas of thinking, such as memory, language, and attention. But how someone approaches tasks is often just as important as the score itself.

Clinicians aim to determine whether symptoms are linked to mood, stress, neurological disease, or a combination of factors. Spending time with a person, hearing their story, and understanding their day-to-day life is a crucial starting point for interpreting any further tests that may be ordered next.

Alzheimer’s disease begins long before symptoms appear

Over recent decades, research has changed how we understand Alzheimer’s disease. We now know that the biological changes linked to Alzheimer’s begin many years, often decades, before noticeable symptoms appear.

Studies show that amyloid changes in the brain can start 15 to 20 years before memory or thinking problems are detected. Changes in tau tend to follow, along with many other things, with cognitive changes appearing later. Importantly, though, this doesn’t mean that everyone with Alzheimer’s pathology will develop dementia. Many factors influence whether and how symptoms emerge, and understanding and predicting this course is a crucial task that researchers in Aotearoa New Zealand and around the world are engaged with.

Importantly, this means a person can have Alzheimer’s disease pathology in their brain without yet having dementia – or even any noticeable problems. Although we’re not at this stage yet, in the future, it may be that a goal of Alzheimer’s treatment – at least for some people – is to prevent the development of dementia at all.

New diagnostic tools – what they can and can’t tell us

In people who have developed problems with their thinking, new tools now allow clinicians to diagnose Alzheimer’s disease with more confidence, although they must be interpreted alongside symptoms and patient history.

Up to this point, these tests have included spinal fluid tests (requiring a lumbar puncture) and amyloid PET scans. These tests are designed to answer a specific question: Is Alzheimer’s disease pathology present? Unfortunately, though, access is limited and not straightforward. Some tests aren’t publicly funded in Aotearoa, and specialist expertise is needed to use them well. Importantly, though, blood tests that can answer the same question – is Alzheimer’s pathology present? – are emerging and, hopefully, will become available in Aotearoa in the near future.

It is important to emphasise that these tests don’t replace clinical assessment. They also can’t yet tell us exactly how quickly an individual’s symptoms will progress or what their future will look like. Results still need to be interpreted alongside a person’s symptoms, history and overall health. They work best when used to support careful diagnosis, rather than as stand-alone answers.

Emerging treatments – progress with limits

Recently, two different medications (Lecanemab and Donanemab) have been approved in many countries for use in early Alzheimer’s disease. This is based on good-quality clinical trial data showing that these agents, which clear amyloid plaques from the brain via the body’s immune system, modestly slow the rate of cognitive decline. These medications are not currently available in Aotearoa.

It’s important to be clear about what these treatments can and can’t do. They don’t restore lost memory or thinking abilities, and they’re not a cure. They do aim to modify the course of Alzheimer’s, and their benefit may be greatest when used early, before significant brain damage has occurred, although there is still much we need to understand about this.

These therapies also come with risks, including brain inflammation. They’re also expensive, and most governments worldwide (including Australia and the United Kingdom) aren’t currently paying for them. Research continues to explore whether treating earlier, even before symptoms appear, could have a greater long-term effect. Broadly, though, the emergence of these new therapies further emphasises the importance of improving pathways for diagnosis and care for all people with cognitive symptoms and Alzheimer’s disease.

What this means for people and whānau now

This evolving research landscape shouldn’t distract from the point that early clarity matters.

A clear diagnosis can help people make informed decisions about work, driving, finances and living arrangements. It can open access to support services and allow time for planning and conversations that may become more difficult as options narrow.

But a diagnosis is also just one point along a person’s journey. What follows – practical support, good information, and ongoing connection – is crucial and relies on collaboration between clinicians, dementia services, primary care and local supports. Diagnosis should open doors to support, not close them.

Looking ahead

Understanding of Alzheimer’s disease is moving quickly. New tools are improving diagnostic accuracy, and treatments that once seemed out of reach are now being tested and implemented in clinical settings.

No single service can do this alone. Good care depends on coordination among specialist services, primary care, and community organisations. Access to specialist care isn’t the same everywhere, and closing those gaps remains important. Collaboration across groups will be crucial as overall management of Alzheimer’s disease undergoes a paradigm shift over the coming years.

For now, the key message is simple: clarity helps. Being listened to matters. And planning, support and compassion remain just as important as any test or treatment.