98 Percent of People With Alzheimer's Develop This Symptom First, Study Says

People over 65 should keep an extra eye out for this dementia symptom.

Right now, more than six million Americans are living with Alzheimer's disease (AD), a form of dementia that destroys memory and the ability to function normally. It's the sixth leading cause of death in the United States, but how exactly it develops can be different for each person. Now, a new study has found that in those with late-onset Alzheimer's dementia (LOAD)—meaning those in which the first symptoms appear past the age of 65—98 percent of patients develop one symptom first. Read on to find out which symptom may appear before others in late-onset cases, and how to spot it.

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In late-onset cases, 98 percent of patients experience depression as a first symptom.

older man with his head in his hands

Experts have long reported that the majority of dementia cases begin with mild cognitive impairment. However, research suggests that in the case of late-onset Alzheimer's disease—defined as cases in which the first symptoms appear after the age of 65—there's an additional symptom that's missing from this picture.

According to a 2017 study published in the journal BMJ Open, depression occurs as a first symptom of late-onset Alzheimer's with nearly the exact same frequency as cognitive impairment—a fact which distinguishes it from early-onset cases of the condition. "We found that depression and cognitive impairment were the first symptoms to appear in 98.5 percent and 99.1 percent of individuals in a study with late-onset AD (LOAD) and 9 percent and 80 percent, respectively, in early-onset AD (EOAD)," the team wrote.

This data suggests that depression occurs as a compounding first symptom in the vast majority of late-onset cases of Alzheimer's, while being relatively rare as a first symptom in early-onset cases. This is especially relevant, given that the National Institute on Aging estimates that 90 percent of Alzheimer's cases are considered late-onset.

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Depression may look different in Alzheimer's patients.

sad older white woman sitting on a couch

Though Alzheimer's-related depression is considered common, it may be more challenging to spot than depression in the general population. "Identifying depression in someone with Alzheimer's can be difficult, since dementia can cause some of the same symptoms," explains the Alzheimer's Association. "In addition, the cognitive impairment experienced by people with Alzheimer's often makes it difficult for them to articulate their sadness, hopelessness, guilt, and other feelings associated with depression," their experts say. Symptoms shared between depression and dementia include apathy, loss of interest in activities, social withdrawal, isolation, difficulty concentrating, and impaired thinking.

The organization also notes that depression associated with Alzheimer's disease may look a bit different from depression in the general population. Depression in AD patients may be less severe, last a shorter period of time, or come and go intermittently. AD patients with depression may also be less likely to talk about or attempt suicide than other people with depression.

Targeting depression may help slow the progression of AD.


In those with Alzheimer's, abnormal levels of brain amyloid—a naturally occurring protein—bond to form plaques that collect between neurons in the brain. This disrupts cell function, contributing to cognitive impairment, experts say. According to Harvard Health Publishing, there's evidence to suggest that depressed individuals with abnormal levels of brain amyloid may experience quicker cognitive decline, including changes in memory and thinking.

"Our research found that even modest levels of brain amyloid deposition can impact the relationship between depression symptoms and cognitive abilities," said Jennifer Gatchel, HMS, assistant professor of psychiatry and a geriatric psychiatrist at Mass General. "This raises the possibility that depression symptoms could be targets in clinical trials aimed at delaying the progression of Alzheimer's disease. Further research is needed in this area," she said.

Gatchel adds that because depression "may be among the early changes in the preclinical stages of dementia syndromes," recognizing it could create "a clinical window of opportunity for closely monitoring at-risk individuals and for potentially introducing interventions to prevent or slow cognitive decline."

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Treatment can improve quality of life in AD patients.

A senior man being hugged by his wife while taking a pill and sitting on the couch

Identifying depression is the first step to treating it. However, in Alzheimer's patients, this may present its own set of challenges. "Because of the complexities involved in diagnosing depression in someone with Alzheimer's, it may be helpful to consult a geriatric psychiatrist who specializes in recognizing and treating depression in older adults," recommends the Alzheimer's Association.

They add that The National Institute of Mental Health has established a separate set of guidelines for diagnosing depression in AD patients. "Although the criteria are similar to general diagnostic standards for major depression, they reduce emphasis on verbal expression and include irritability and social isolation," their experts note.

Once diagnosed, many Alzheimer's patients benefit from a combination of medication, counseling, and lifestyle interventions including "gradual reconnection to activities and people that bring happiness."

Speak with your doctor today about whether screening or treatment may be right for you.

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Lauren Gray
Lauren Gray is a New York-based writer, editor, and consultant. Read more
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