By Glenn Ellis
On Sunday, during my health segment on “Rewind with Patty Jackson,” Patty and I talked about something that has been on a lot of minds since the news about Sir Patrick Stewart. I only have a few minutes on the air, and this topic deserves more than that. So let’s keep the conversation going.
When we lost Sir Patrick Stewart last month, many people learned something surprising: he had two forms of dementia at the same time, Alzheimer’s disease and Lewy body dementia. Doctors call this mixed dementia.
Chances are, you’ve never heard of it. You’re not alone. Lewy body dementia affects an estimated 1.4 million Americans, yet a Mayo Clinic neurologist once called it “the most common disorder you’ve never heard of.” When it occurs alongside Alzheimer’s, it’s even easier to miss, and that can mean the wrong diagnosis and the wrong treatment.
In this follow-up, I want to go a little deeper into what mixed dementia is, why a loved one can seem sharp at breakfast and confused by dinner, and what to ask the doctor so you get the right diagnosis and the right care.
This hits close to home. About 282,000 Pennsylvanians 65 and older are living with Alzheimer’s, including an estimated 34,000 right here in Philadelphia, the highest rate of any county in the state. And about 472,000 Pennsylvanians are caring for a loved one with dementia.
What Is Mixed Dementia?
Dementia isn’t one disease. It’s an umbrella term for a decline in memory, thinking, and reasoning serious enough to interfere with daily life. Alzheimer’s disease is the most common cause, but it isn’t the only one. Mixed dementia means that more than one disease is damaging the brain at the same time.
Sir Patrick’s family said he died after “a brief and poignant journey” with both Alzheimer’s disease and Lewy body dementia. That combination is more common than most people realize. According to the Alzheimer’s Association, Lewy bodies are the second most common type of brain change found alongside Alzheimer’s disease at autopsy. In other words, many people who are told they have “just Alzheimer’s” may actually be living with more than one condition.
How Common Is Dementia?
Sir Patrick’s story is one of millions. Around the world, an estimated 57 million people were living with dementia in 2021, according to the World Health Organization (WHO), and there are nearly 10 million new cases every year. Alzheimer’s disease accounts for an estimated 60 to 70 percent of those cases.
Here at home, the Alzheimer’s Association’s 2026 report, Alzheimer’s Disease Facts and Figures, estimates that 7.4 million Americans age 65 and older are living with Alzheimer’s dementia. That’s about 1 in 9 people in that age group.
Age is the biggest risk factor. About 5 percent of people ages 65 to 74 have Alzheimer’s dementia, compared with nearly 14 percent of those ages 75 to 84 and about 36 percent of those 85 and older. Almost two-thirds of Americans with Alzheimer’s are women. Women’s longer life expectancy is part of the reason, but researchers are still working to understand the full picture. Older Hispanic Americans are about one and a half times as likely as older white Americans to have Alzheimer’s or another dementia, and older Black Americans are about twice as likely, a disparity I’ll come back to below. And dementia isn’t only a disease of old age. Worldwide, young-onset dementia, in which symptoms begin before age 65, accounts for up to 9 percent of cases.
These numbers are expected to grow, mainly because people are living longer. The number of Americans 65 and older is projected to rise from 65 million in 2026 to 82 million by 2050. Without new ways to prevent, slow, or cure the disease, the Alzheimer’s Association projects that the number of older Americans living with Alzheimer’s could reach 13.8 million by 2060. Globally, WHO has projected that the number of people living with dementia could reach 139 million by 2050.
There is some encouraging news, too. Several studies suggest that the rate at which older adults develop dementia has actually declined in recent decades. And WHO now says that up to 45 percent of dementia risk can be linked to factors we can do something about, such as high blood pressure, diabetes, smoking, physical inactivity, and social isolation. The total number of cases is rising because our population is aging, but dementia is not an inevitable part of growing older.
Two Different Diseases
To understand why the combination matters, it helps to know how each disease works on its own.
Alzheimer’s disease is driven by two abnormal proteins: amyloid, which builds up into plaques between brain cells, and tau, which forms tangles inside them. It usually begins quietly, with trouble remembering recent conversations, repeating questions, or misplacing things. Over time, it affects language, judgment, and the ability to manage everyday tasks.
Lewy body dementia is caused by clumps of a different protein, called alpha-synuclein, that form inside nerve cells. These clumps are known as Lewy bodies. Early on, memory may be less affected than in Alzheimer’s. Instead, families often notice:
· Swings in alertness and attention, from clear and engaged one moment to confused, drowsy, or staring into space the next
· Visual hallucinations, often detailed images of people or animals that aren’t there
· Acting out dreams during sleep, such as shouting, punching, or kicking
· Movement problems similar to Parkinson’s disease, including stiffness, slowness, a shuffling walk, and falls
· Dizziness, fainting, or sudden drops in blood pressure when standing
Those swings in alertness are why a loved one can seem sharp at breakfast and confused by dinner. Families sometimes wonder whether their loved one is “faking it” or whether they are imagining the good days. They aren’t. Fluctuation is one of the hallmarks of Lewy body disease.
Why It’s So Easy to Miss
When Alzheimer’s and Lewy body disease occur together, the symptoms overlap and blur. Memory loss can make it look like Alzheimer’s alone. Hallucinations might be blamed on medication or a urinary tract infection. A shuffling walk and stiffness might lead to a diagnosis of Parkinson’s disease. Each piece gets explained away, and the full picture never comes into focus.
There is also no single test that confirms Lewy body dementia. Diagnosis relies on a careful history, a neurological exam, and sometimes specialized tools, such as a sleep study, certain brain scans, or newer tests that look for the abnormal alpha-synuclein protein. Many families see several doctors before they get a clear answer. The most important information often comes from the people who see the person every day.
Why the Right Diagnosis Matters
This is not just about putting the right label on a chart. Getting the diagnosis right can change care in real ways.
Medication safety. Many people with Lewy body dementia are highly sensitive to antipsychotic medicines, which are sometimes used to calm agitation or hallucinations, especially in hospitals and nursing homes. In these patients, the drugs can cause severe confusion, rigidity, falls, and other dangerous reactions. If the care team doesn’t know Lewy bodies are involved, a well-meaning prescription can make things much worse.
Treatments that may help. Medicines called cholinesterase inhibitors, such as donepezil and rivastigmine, are used for Alzheimer’s and are often helpful for people with Lewy body dementia as well. Sleep problems, blood pressure changes, and movement symptoms can also be treated once they’re recognized.
Newer Alzheimer’s drugs. The newer anti-amyloid medications for early Alzheimer’s target amyloid, not Lewy bodies, and they carry risks of their own, including brain swelling and bleeding. Whether and how much they help people with mixed dementia is still an open question. That’s a conversation to have carefully with a specialist.
Planning ahead. Lewy body dementia can change quickly, and it brings safety concerns, such as falls and nighttime behaviors, that families need to prepare for. Knowing what you’re dealing with helps you plan for care, finances, and support before a crisis.
Questions to Ask the Doctor
If someone you love has memory problems, or a dementia diagnosis that doesn’t seem to explain everything you’re seeing, bring these questions to the next appointment:
· Could more than one condition be causing these symptoms?
· Have you considered Lewy body dementia, given the hallucinations, sleep behaviors, movement changes, or ups and downs in alertness?
· Should we see a neurologist, geriatric psychiatrist, or memory specialist?
· Are any of the current medications risky for someone who might have Lewy body disease?
· What should we do, and who should we call, if confusion or hallucinations suddenly get worse?
It also helps to keep a simple diary of good days and bad days, unusual behaviors, sleep problems, and falls. Bring it with you. Doctors may see a person for only 15 minutes, and that diary can show them what they would otherwise miss. And don’t be shy about speaking up. You know your loved one better than anyone else in that exam room.
For the Caregivers
Behind every person living with dementia, there is usually someone caring for them, often a spouse, a daughter, or a son doing it with little help. Here in Philadelphia, that burden doesn’t fall evenly. Older Black Americans are about twice as likely as older white Americans to have Alzheimer’s or another dementia, and they are often diagnosed later, when there are fewer options. That is one more reason to speak up early and ask questions.
If you are a caregiver, you don’t have to figure this out alone. The Alzheimer’s Association’s free 24/7 Helpline and the Lewy Body Dementia Association’s Lewy Line can answer questions, point you to local resources, and connect you with support groups. And please take care of your own health, too. You can’t pour from an empty cup.
Let’s Keep Talking
Sir Patrick Stewart spent a lifetime helping us imagine the future. In his final chapter, he left us something else: a reason to talk openly about a disease too many families face in silence. My thanks to Patty Jackson for making room for this conversation, and to everyone who tuned in on Sunday. If you have questions about mixed dementia, or a health topic you’d like us to take on next, keep them coming.
Remember, I’m not a doctor. I just sound like one. Take good care of yourself and live the best life possible!
#informationisthebestmedicine
Glenn Ellis is a medical ethicist, health educator, and writer whose work centers on health equity and ethics in medicine. For more good health information, visit www.glennellis.com.
