Years after the beginning of the COVID-19 pandemic, researchers continue to study its far-reaching effects on the body. COVID-19 was initially understood to be primarily a respiratory illness, but we now know that SARS-CoV-2 (the virus that causes the illness) or coronavirus can affect organs beyond your lungs. People can experience the long-term effects of COVID-19, often called “long COVID,” for months or years after initial symptoms like fever and a runny nose are long gone. These lingering issues can include fatigue, difficulty concentrating (often called “brain fog”), and other neurological symptoms, highlighting the virus’s broader impact.

While research into the link between COVID-19 and Alzheimer’s disease continues, it’s clear that the relationship is complex. Having COVID-19 can impact your Alzheimer’s disease risk, and Alzheimer’s disease can change the way COVID-19 affects you. In this article, we share five important facts to know about the link between the two diseases, including information on how to protect yourself or a loved one with Alzheimer’s from a future COVID-19 infection.

1. Alzheimer’s Increases Your COVID-19 Risk

If you or a loved one has Alzheimer’s disease, it’s important to be aware that having Alzheimer’s puts you at a higher risk of COVID-19. In general, older people are more at risk. Below are two factors that particularly impact people with Alzheimer’s.

Forgetfulness of Prevention Strategies

Confusion and memory problems can make it harder for someone to protect themself from catching COVID-19 or other respiratory infections. They might forget they already washed their hands and do it repeatedly, or, more concerningly, they might completely forget to wash their hands after being in a public place. They also may not remember to take other precautions like wearing a mask in higher-risk situations.

Caregivers and family members have the opportunity to support people with Alzheimer’s in preventing COVID-19. If you’re a caregiver of someone with Alzheimer’s disease or dementia, you can help them take steps that reduce the risk of getting sick. This might involve gentle reminders about handwashing, assistance with putting on and taking off masks, ensuring they maintain a safe distance in public, and helping them stay up-to-date with vaccinations.

Close Quarters in Residential Care

People with Alzheimer’s or dementia living in residential care homes have an added layer of risk for COVID-19. They live closely with other residents and staff. In shared areas, coronavirus can spread from person to person.

Older adults in nursing homes tend to be frailer, making them more susceptible to infections due to age-related weakening of the immune system.

2. COVID-19 Can Increase Your Alzheimer’s Risk

Severe COVID-19 infections can lead to an increased risk of dementia and Alzheimer’s disease in the future. A severe COVID-19 infection can also make someone more likely to develop other psychiatric and neurological conditions, such as depression, obsessive-compulsive disorder (OCD), and Parkinson’s disease.

Experts believe coronavirus causes changes in the brain, brain stem, and spinal cord — the central nervous system (CNS). They have a couple of theories on how this happens: COVID-19 might trigger the release of neurotoxins that damage nerve cells, or COVID-19 activates the immune system and causes it to damage nerve cells with widespread neuroinflammation (inflammation in the CNS).

Coronavirus also causes oxidative stress in your body as part of the immune response. Oxidative stress means you have too many free radicals (unstable molecules that damage cells) and not enough antioxidants (molecules that protect your cells from free radicals) to fight them. Oxidative stress damages nerve cells, which can cause or worsen Alzheimer’s disease.

3. COVID-19 Affects People With Alzheimer’s Differently

Some symptoms and long-term effects of COVID-19 are more common in people with Alzheimer’s disease or other forms of dementia. Many people with Alzheimer’s experience more severe COVID-19 illness, especially if they have other conditions like diabetes or heart disease, which can weaken the body’s ability to fight off the virus and increase inflammation.

Delirium

Delirium, which involves disorientation and trouble thinking clearly, is the No. 1 COVID-19 symptom in people with dementia. One study showed that 82.4 percent of people with dementia experienced delirium at the start of a COVID-19 infection. Delirium can increase Alzheimer’s symptoms one already has, such as confusion. Recognizing delirium as a potential early sign of COVID-19 is crucial in this population.

Fewer Typical COVID-19 Symptoms

Some of the symptoms you might associate with COVID-19 are less likely to affect people with dementia during an infection, including:

• Chills
• Shortness of breath
• Nausea and vomiting
• Headache
• Body aches

Other common symptoms, weakness and fever, appear in over 70 percent of COVID-19 cases affecting people with Alzheimer’s, making them the second- and third-most common COVID-19 symptoms in people with dementia, after delirium.

Lost Sense of Smell

Anosmia (losing your sense of smell) is a common early symptom of COVID-19. People with a specific gene variant, the e4 allele of apolipoprotein E4 (APOE4), have an increased risk of developing anosmia with COVID-19. APOE4 is also the strongest risk factor for Alzheimer’s disease. Over 25 percent of people carry at least one copy of this gene, but it is crucial to understand that not all people with the APOE4 gene will develop Alzheimer’s. This shared genetic link is an area of ongoing research.

Worsening Cognitive Decline

COVID-19 can speed up the progression of Alzheimer’s disease and other forms of dementia. This likely happens for a few reasons:

• The virus damages cells in the brain that control learning, thinking, and memory.
• Delirium heightens Alzheimer’s disease symptoms.
• Intensive care in hospital settings makes people with Alzheimer’s more confused.
• Long COVID causes confusion and brain fog for months or years after initial COVID-19.
• Social distancing during infections might affect a person’s mental health and cognitive function.

While COVID-19 can worsen Alzheimer’s symptoms, it’s encouraging to know that targeted treatment and rehabilitation strategies can help improve some symptoms that got worse because of COVID-19. This might include cognitive rehabilitation exercises to help regain some cognitive function, occupational therapy to assist with daily living activities, and supportive care to address emotional and behavioral changes.

Lower Survival Rate

People with Alzheimer’s disease have a lower COVID-19 survival rate than those who don’t have Alzheimer’s disease. This means COVID-19 is more likely to lead to death, possibly due to factors such as increased frailty, the presence of other underlying health conditions, and potentially, a less effective immune response to the virus.

4. Some Therapies Can Improve Your Outcome

Evidence-based treatments can lead to better outcomes for people with Alzheimer’s disease after COVID-19 by preventing or lessening nervous system damage.

• Antioxidant therapy — Antioxidants like vitamin E can help reduce oxidative stress in the brain from COVID-19 so it doesn’t make Alzheimer’s disease worse.
• Acetylcholinesterase inhibitors — These medications stop acetylcholine, an important molecule in your brain and nervous system, from breaking down.
• Memantine — This treatment can slow Alzheimer’s disease progression.
• Nutrition therapy — Some nutritional treatments might improve outcomes for people with Alzheimer’s disease after COVID-19. For example, prebiotics like wheat bran might slow the progression of Alzheimer’s disease.
• Exercise — Physical exercise can help slow Alzheimer’s progression after COVID-19 by reducing inflammation and oxidative stress and increasing blood flow in the brain.

5. You Can Stay Safe From COVID-19

If you’re a loved one or caregiver of someone with Alzheimer’s disease, you can help them reduce their COVID-19 risk to avoid Alzheimer’s progression and other COVID-19 health complications.

The most effective way to prevent COVID-19 is by getting COVID-19 vaccinations. The COVID-19 vaccine — including various types that have been rigorously tested and proved safe and effective for older adults and individuals with cognitive impairment — can greatly reduce the risk of severe COVID-19 illness and its potentially devastating health complications.

You might worry about taking a loved one with Alzheimer’s to get a shot. However, it’s crucial to remember that vaccination is a vital preventive measure, especially for this vulnerable population, precisely because contracting COVID-19 can lead to a worsening of dementia. Members of myALZteam have shared encouraging messages about getting the COVID-19 vaccine:

• “My husband, who has Alzheimer’s/dementia, had the COVID-19 shot and he was fine. It did not affect him at all. Not even a sore arm.”
• “It is my understanding that having COVID-19 can cause a worsening of dementia. Any trauma can do that. However, the vaccine doesn’t cause any problems, and in preventing COVID-19, it is a must for a dementia patient as well as the caregiver.”
• “We’ve had both shots. Happy to say, no side effects!”

The vaccine is generally safe and won’t interact negatively with Alzheimer’s medications. It won’t make Alzheimer’s worse or cause it in someone who doesn’t have it. Still, if a person with Alzheimer’s disease can make medical decisions for themself, it’s up to them to decide whether to get the COVID-19 vaccine.

You can also help reduce COVID-19 risk for a person with Alzheimer’s disease by encouraging them to wash their hands frequently and making sure their living space has good airflow. You can also encourage a loved one with Alzheimer’s to wear a mask over their mouth and nose in crowded areas.

Talk With Others Who Understand

On myALZteam, the social network for people with Alzheimer’s disease and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with Alzheimer’s disease.

Have you or a loved one had COVID-19 with Alzheimer’s disease? What steps have you taken to reduce your risk? Share your experience in the comments below, or start a conversation by posting on your Activities page.