dementia stages

Dr. Zaldy Tan On the Stages of Dementia

By | February 23rd, 2021

Dr. Zaldy Tan of the Cedars-Sinai's Memory & Aging Program discusses the symptoms of early, middle and late -stage of dementia, and shares why some people experience a faster decline than others.

The progression of dementia is often unpredictable as people’s symptoms can ebb and flow. But, clinicians can distinguish the different stages of dementia, identifying the common symptoms that characterize each phase and helping patients and families plan ahead. We spoke with Dr. Zaldy Tan about the stages of the disease.

  • Dr. Tan urged people living with dementia and their caregivers to ask their doctors the question, ‘What stage of dementia am I or my loved one in?” It starts the conversation between patients, families and doctors to plan for treatment, day-to-day needs and care services appropriate for the person’s specific stage of dementia.
  • Caregivers should describe in detail about the symptoms they have observed in the person they are caring for, providing clues for the clinician to determine the stage of dementia.
  • While people with Alzheimer’s typically experience a slow progression of the disease, those who also have vascular dementia and experience mini-strokes could suffer from a more rapid decline. Meanwhile, people with dementia who are hospitalized can have a quicker deterioration in their condition than previously expected.

Being Patient: What are the various stages of dementia? 

Dr. Zaldy Tan: There are many scales for the different stages of dementia. For the general caregiver or family members, I want to simplify it to thinking of it as a continuum … Some people say mild, moderate, severe, but I try to avoid that because when [someone says], “You have severe dementia,” typically it’s a bit disconcerting, when in reality, some people in the late stage have severe symptoms, but they don’t have severe psychosocial issues. I like to think of it as early, middle and late stages.

One of the things that I’ve found in my practice is that, unlike for example with cancer or other progressive chronic diseases, people don’t think about dementia as stages, when in fact, any progressive chronic disease should be thought of as stages because it allows us to monitor the symptoms, plan for the future, and for health professionals to help educate families of what to expect next. And I think that is truly important. 

[Identifying the stages of dementia is] extremely important from a research standpoint. Clinical trials are aimed specifically at specific stages of dementia. A lot of the prevention trials are targeting either [mild cognitive impairment] stage or very early dementia. Knowing what cutting edge treatments or research or clinical trials your loved one might be eligible for, it’s important to know what stage they’re in in order to participate in the scientific process and discovery. 

From a practical standpoint, there are characteristics of each stage that will allow one to anticipate the things that they will need, and the things that they should be left to do on their own. A good example would be driving … I have some patients with mild dementia … and they’re still able to drive short distances, in good weather and in daytime. That’s a good example of some things that may be very important to the patient but you don’t want to take it away if they’re still able to do it safely, albeit you have to monitor it. 

As much as we want to anticipate where the patient will be, we also want to know what they can still do for themselves so that we can allow them as much independence and ability to do things in their own terms. 

Being Patient: Why do some people with dementia progress faster than others? 

Dr. Zaldy Tan: I see [a faster decline] frequently in people with vascular dementia. When patients ask me, “How long before this progresses to the next stage?” I’d be like, “It depends when the next stroke happens.” 

We know that a lot of people with so-called Alzheimer’s disease actually have mixed dementia. It’s not just the neurofibrillary tangles and the amyloid plaques that are causing the nerve cells to die, but a lot of people have small strokes that can cause change pretty abruptly. 

But if it’s pure Alzheimer’s disease, you don’t expect these abrupt changes. In fact, one of the characteristic symptoms of Alzheimer’s disease is this slow smoldering progression. 

The other thing is that hospitalizations are bad for people with dementia. If you have someone with mild dementia, and they get an infection or they get a hip fracture, god forbid and they end up in a hospital, then it’s been shown that when they get out of the hospital, they may not be able to get back to their previous baseline. That’s another reason why someone will progress more rapidly than expected.

Being Patient: In some ways, knowing a loved one’s specific stage of dementia helps caregivers prepare themselves for what’s ahead, doesn’t it?  

Dr. Zaldy Tan: Certainly caregivers are looking out for their loved one so that they could be physically, financially, emotionally prepared for what’s to come next. 

But also we have to understand that the person with dementia themselves are also going through their own journey. I find people with early dementia can become socially isolated if without the support of the caregiver and their loved ones. For example, they have many friends and some of the closest ones may not be able to deal with dementia and adjust to it. In the early stage of dementia, you can anticipate that you’re going to lose some friends, and even more so when you get to the middle stage. That anticipatory need for what is to come next is very important. 

Being Patient: There seems to be a lot of confusion about the different stages of dementia and it can be difficult to anticipate when a person is nearing the end-of-life, can you tell us about some of the common symptoms in the late stage of dementia? 

Dr. Zaldy Tan: I understand why that’s a source of confusion for people because these stages overlap. Take for example ambulation … in the early stage, people can walk without getting lost. At the moderate stage, they could still walk but they could be a bit slower, and they could wander and get lost, hopelessly lost, even though physically they’re still able to ambulate. 

But at the late stage, typically people are getting slow in walking. They can fall. A lot of head trauma can happen during that period. At the late, late stage, what happens is that they become wheelchair-bound or bed-bound. They can get pressure sores from being on their backs for most of the day. That’s the typical progression. 

However, there are people who don’t progress that way, meaning they’re ambulatory till the very end. What may get them in the end may be aspiration pneumonia, or something else altogether. 

Being Patient: Are there any tests that can help clinicians predict how quickly a patient will advance through the stages of dementia? 

Dr. Zaldy Tan: Not at the outset, meaning there are now biomarkers for spinal fluid and there are plasma biomarkers now developing, but I haven’t seen any good studies that show for example if your amyloid beta levels or p-tau217 (a biomarker of tau proteins) is higher, then you are going to progress faster. 

But the interesting thing about biomarkers is now that we have monoclonal antibodies, prevention trials or trials for disease modifying therapies, I predict that these biomarkers will be helpful in terms of predicting who is responding to the treatment. 

Until recently, all we had were performance on cognitive evaluations and functional measures. But if we have a reliable way of measuring the biology of disease, for example, neurofilament light (NfL) is one of the biomarkers that has shown promise in monitoring the progression of neurodegeneration, I predict in the future you can go to your doctor and they will draw blood or give a [spinal tap] and [they may] say, “Your level of this biomarker is stabilized and therefore we’re in good shape.” If it’s increasing, [the doctor may say], “I think we have to do something else.” 

The interview has been edited for length and clarity.

Contact Nicholas Chan at

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