FAST or GDS? How the Two Staging Tools Line Up

What is the difference between FAST and GDS staging?

The Global Deterioration Scale stages primary degenerative dementia by cognition across seven stages, and it came first, in 1982 1Ref 1Reisberg B, Ferris SH, de Leon MJ, Crook T (1982).The Global Deterioration Scale for assessment of primary degenerative dementia.The existence, seven-stage structure, 1982 publication, and clinical origin of the Global Deterioration Scale as a framework for staging primary degenerative dementia by cognitive deterioration.. Functional Assessment Staging keeps the seven-stage architecture but rates what a person can still do without help, and it adds lettered substages inside the later stages 2Ref 2Reisberg B (1988).Functional Assessment Staging (FAST).The FAST scale's seven major stages of functional decline in Alzheimer's dementia, its lettered substages within the later stages, the functional content of those stages, and its use as the staging tool in dementia hospice eligibility.. One tool watches the mind. The other watches the day.

The difference is not severity. It is the question being asked. A person can be far along on one scale and less far along on the other, and neither reading is a mistake.

Why a second scale was written six years after the first

Because a cognitive scale runs out of things to measure before the illness runs out of course. The Global Deterioration Scale describes deterioration in the mind 1Ref 1Reisberg B, Ferris SH, de Leon MJ, Crook T (1982).The Global Deterioration Scale for assessment of primary degenerative dementia.The existence, seven-stage structure, 1982 publication, and clinical origin of the Global Deterioration Scale as a framework for staging primary degenerative dementia by cognitive deterioration., and describing a mind requires a person who can be questioned, tested, and observed responding. Late in Alzheimer's disease — the most common cause of dementia 3Ref 3National Institute on Aging (NIH) (2024).What Is Alzheimer's Disease?.That Alzheimer's disease is the most common cause of dementia and is a progressive brain disorder that gradually destroys memory and thinking skills. — that person can no longer be questioned.

Function has no such ceiling. Whether someone dresses themselves, bathes themselves, walks, sits up, or holds their head up can be observed from across a room by anybody, on any day, without a single question being asked 2Ref 2Reisberg B (1988).Functional Assessment Staging (FAST).The FAST scale's seven major stages of functional decline in Alzheimer's dementia, its lettered substages within the later stages, the functional content of those stages, and its use as the staging tool in dementia hospice eligibility.. The scale keeps producing information long after the interview stops working.

That is the whole reason the 1988 tool exists. It is not a correction of the 1982 one and not a replacement for it. It is the same seven-step map redrawn from a vantage point that stays usable at the end. Clinicians sometimes file both under Reisberg staging, which is accurate about the authorship and misleading about the measurement.

What each scale measures, and who supplies the answer

This is the practical difference, and it decides who in the room is the expert. A cognitive stage rests on what a clinician can elicit — orientation, recall, judgement, awareness of the deficit itself 1Ref 1Reisberg B, Ferris SH, de Leon MJ, Crook T (1982).The Global Deterioration Scale for assessment of primary degenerative dementia.The existence, seven-stage structure, 1982 publication, and clinical origin of the Global Deterioration Scale as a framework for staging primary degenerative dementia by cognitive deterioration.. A functional stage rests on what the household reports: what happened at breakfast, whether the shower needed two people, when the walking stopped 2Ref 2Reisberg B (1988).Functional Assessment Staging (FAST).The FAST scale's seven major stages of functional decline in Alzheimer's dementia, its lettered substages within the later stages, the functional content of those stages, and its use as the staging tool in dementia hospice eligibility..

So the informant changes. For gds staging, the person with dementia is the primary source of evidence, examined directly. For the fast scale, the primary source is whoever provides daily care, because they are the only ones who see an ordinary Tuesday.

That has an awkward consequence worth naming. The cognitive scale depends most heavily on self-report at exactly the stages where insight is already going — which is why families are asked to fill the gap, and why their candour ends up determining the number. A relative who softens the answers to protect a parent's dignity moves the stage, and everyone involved has done that at least once.

When the two numbers legitimately disagree

Regularly, and a mismatch is usually information rather than error. Cognition and function decline together on average and separately in individuals, so a person can look further along on one scale than the other for reasons that have nothing to do with the dementia. The disagreement itself is often the most clinically useful thing on the page.

• Function ahead of cognition. A stroke, a fracture, arthritis, or Parkinsonism can take walking or dressing while conversation is still largely intact. The functional number drops; the cognitive one does not.
• Cognition ahead of function. A physically robust person with severe memory loss may still walk for miles, which is exactly the pattern in which wandering becomes the dominant safety concern rather than physical care 4Ref 4National Institute on Aging (NIH) (2024).Coping With Alzheimer's Behaviors: Wandering and Getting Lost.That people with Alzheimer's may wander and become lost, making wandering a leading safety concern for people who remain physically mobile..
• Fluctuation. Some dementias vary so much between morning and evening that the cognitive stage depends on when the appointment was booked.
• A bad month. Infection, dehydration, pain, poor sleep, or a new medication moves function fast and cognition faster.

Two different numbers for the same person do not mean somebody got it wrong. They mean two things were measured.

Why FAST is the scale on the hospice paperwork

Because eligibility has to rest on something observable by more than one person and repeatable across visits. Functional Assessment Staging is the tool used for dementia hospice eligibility, and the markers that count sit at its later stages 2Ref 2Reisberg B (1988).Functional Assessment Staging (FAST).The FAST scale's seven major stages of functional decline in Alzheimer's dementia, its lettered substages within the later stages, the functional content of those stages, and its use as the staging tool in dementia hospice eligibility.. Nothing about a cognitive stage is easier to document than the plain fact that someone can no longer walk.

That has a knock-on effect families feel directly. Once a person is well into the illness, the fast scale is likely to be the number quoted back to them by hospice teams, long-term-care assessors, and anyone else working from a form. The global deterioration scale dementia stages are more likely to appear in the diagnostic story: what has been happening to the mind, and roughly where in the arc it sits.

Both numbers describe the same person. Neither is the more serious one. It is worth knowing which scale a number came from before repeating it to somebody else, because the same digit means two different things depending on its source.

Where neither scale fits well

Both were built around one illness. The Global Deterioration Scale was written for primary degenerative dementia 1Ref 1Reisberg B, Ferris SH, de Leon MJ, Crook T (1982).The Global Deterioration Scale for assessment of primary degenerative dementia.The existence, seven-stage structure, 1982 publication, and clinical origin of the Global Deterioration Scale as a framework for staging primary degenerative dementia by cognitive deterioration. and the functional tool was written to describe decline in Alzheimer's disease 2Ref 2Reisberg B (1988).Functional Assessment Staging (FAST).The FAST scale's seven major stages of functional decline in Alzheimer's dementia, its lettered substages within the later stages, the functional content of those stages, and its use as the staging tool in dementia hospice eligibility. — the most common cause of dementia, but far from the only one 3Ref 3National Institute on Aging (NIH) (2024).What Is Alzheimer's Disease?.That Alzheimer's disease is the most common cause of dementia and is a progressive brain disorder that gradually destroys memory and thinking skills.. The further a person's illness sits from that template, the worse both sequences fit.

The misfits are recognisable. An illness that takes behaviour and language early while leaving self-care intact for years does not step through either scale in order. An illness that drops in steps and then holds flat produces a stage that is accurate for a year and then wrong overnight. An illness that fluctuates by the hour produces a stage that depends on the hour.

When that happens, a clinician who stops reaching for a number and describes the actual day instead is doing the better thing. The broad three-part description — early, middle, late — survives in general use partly because it does not pretend to a precision the finer scales imply 5Ref 5Alzheimer's Association (2024).Stages of Alzheimer's.That Alzheimer's is commonly described in three broad stages — early, middle, and late — as a general-purpose description of the illness's course..

What to ask so the number means something

Ask which scale it came from. That single question resolves most of the confusion these two tools create, because a stage quoted without its source is only half a fact. After that, ask what the reasoning was — the observation behind the number is the part a family can actually act on at home.

A second technique is worth borrowing from clinicians. Health-literacy guidance recommends structuring conversations so that everyone understands regardless of background, using plain language and teach-back — having the listener say back what they heard so gaps surface immediately 6Ref 6Agency for Healthcare Research and Quality (2024).Health Literacy Universal Precautions Toolkit, 3rd Edition.That health-literacy universal precautions means structuring communication so every patient can understand regardless of literacy level, using evidence-informed techniques including plain language and teach-back.. Families can invite it: repeating the stage and its meaning back in your own words, and asking whether that is right, catches the misunderstanding while the clinician is still in the room.

• Write the stage down with the date. Direction matters more than any single reading.
• Ask what the next change is likely to be, not how long there is.
• Ask whether anything treatable could be depressing the number today.

So which one should a family use?

Whichever one the people making decisions about this person are using — plus the translation. There is no prize for picking the better scale, and no version of this where a family needs to become fluent in both. What matters is not repeating a number into a context that reads it differently.

Early on, the cognitive picture usually carries more meaning: gds stage 4 and gds stage 5 describe an illness that is still mostly about judgement, planning, and independence rather than about physical care. Later, the functional picture carries more: by gds stage 6 and fast stage 6, the useful information is about dressing, bathing, and continence, which is also the vocabulary that memory care criteria and care plans are written in.

The scale is a shared language, not a verdict. Its value is letting a family, a clinician, and an assessor describe the same person without a long preamble. It cannot tell anyone whether they are doing enough, and it was not built to try.