New Model Predicts Five Years of Alzheimer's Cognitive Decline

For people diagnosed with Alzheimer's disease, one of the most frightening aspects can be the uncertainty around what comes next for them and their carers. A new study may help make that prognosis less mysterious.

Researchers have created a tool designed to project cognitive decline over the following five years in people showing early signs of Alzheimer's.

Although dementia progresses differently from one person to another, the team produced its prediction model through a detailed examination of real patients.

"People are very interested in what to expect from the disease in themselves or their loved ones, so better prediction models are urgently needed," says physician-researcher Pieter van der Veere of Amsterdam University in the Netherlands.

Alzheimer's disease patients and the prediction model

Van der Veere's team assessed 961 patients with an average age of 65. Of these, 651 had mild dementia and 310 had mild cognitive impairment. Every participant also had amyloid beta plaques - protein deposits in the brain associated with Alzheimer's disease, the most common type of dementia.

The researchers closely examined MRI scans and biomarkers obtained from cerebrospinal fluid. They additionally considered each patient's age, gender, medical history and cognitive-test results over time, with the tests scored out of 30.

A score above 25 signified no dementia. Scores from 21 to 24 indicated mild dementia, 10 to 20 indicated moderate dementia, and any score below 10 was classified as severe dementia.

Cognitive decline over five years

On average, patients with mild cognitive impairment recorded an initial test score of 26.4, which fell to 21 after five years. Those with mild dementia declined considerably faster, dropping from 22.4 to 7.8 over the same five-year period.

The team could also simulate the impact of medication.

"In the future, this will become even more important if we can treat Alzheimer's disease," says neuroscientist Wiesje van der Flier of Amsterdam University.

"This can be a starting point for conversations between doctor, patient and family about the pros and cons of treatments, so that they can come to an appropriate decision together."

How medication could affect predicted outcomes

The models suggest that someone with mild cognitive impairment and a baseline cognitive-test score of 28 could reach moderate impairment in six years. If medication reduced their decline rate by 30 percent, it would take 8.6 years to reach moderate impairment.

For a patient with mild dementia beginning at a score of 21, moderate impairment would be reached in 2.3 years. With medication slowing the decline, this would extend to 3.3 years.

Actual results can differ substantially. Half of the patients with cognitive impairment had scores within two points of the forecast, while half of the dementia patients were within three points. This indicates that the models may help people understand cognitive decline, but that reaching a confident prognosis can still be difficult.

Even so, the results are encouraging. Incorporating as many parameters as possible allows the model to generate an individualised outcome, giving patients and their loved ones a clearer sense of what may happen as the disease advances - provided medical practitioners clearly communicate the uncertainty involved.

The researchers also hope to improve the work further and develop more accurate prediction models.

"We understand that people with cognitive problems and their care partners are most interested in answers to questions like 'How long can I drive a car?' or 'How long can I keep doing my hobby?'" Van der Veere says.

"In the future, we hope that models will help make predictions about these questions about quality of life and daily functioning. But until then, we hope these models will help physicians translate these predicted scores into answers for people's questions."

The research was published in Neurology.