Is Dementia Hereditary? What Families Ask Before a Move

When a parent is diagnosed with dementia, the adult children in the room are thinking about two people: the parent in front of them, and themselves. Is this going to happen to me is the question they ask me in the parking lot after the tour, not in the conference room. I asked it myself when my mother was sick.

Most dementia is not directly inherited. Having a parent or sibling with Alzheimer’s raises your risk somewhat, and certain genes raise or lower it further, but only a small share of cases come from a single gene that is passed down. Family history is a reason to take your own brain health seriously. It is not a sentence.

The short answer: risk runs in families, the disease usually does not

Dementia is an umbrella term for memory and thinking loss severe enough to interfere with daily life, and Alzheimer’s disease is the most common cause. For the vast majority of people, Alzheimer’s develops from a mix of age, genes, health and environment, with age as the biggest factor by far. Published research puts the directly inherited forms at a small fraction of all cases.

Having a first degree relative with Alzheimer’s, meaning a parent or sibling, does raise your odds compared with someone with no family history, and having more than one affected relative raises them further. But most people with an affected parent never develop dementia, and many people with dementia have no family history at all. That is the pattern of a risk factor, not of a hereditary disease.

Risk genes versus deterministic genes

There are two kinds of genes in this conversation, and the difference is everything.

Risk genes

A risk gene changes the odds without deciding the outcome. The best known is APOE, which comes in several forms. One form, often written APOE e4, raises the chance of late onset Alzheimer’s and may bring it on a few years earlier. Inheriting one copy raises risk; two copies raise it more. Plenty of people with two copies never develop the disease, and plenty of people with none do.

Deterministic genes

A deterministic gene causes the disease in anyone who inherits it. In Alzheimer’s these are rare mutations in three genes, usually written APP, PSEN1 and PSEN2, and they cause early onset familial Alzheimer’s, often with symptoms in a person’s forties or fifties. These families usually know, because the pattern across generations is unmistakable. Huntington’s disease is another deterministic condition that produces dementia, and some forms of frontotemporal dementia run in families through specific genes.

If your parent developed symptoms in their seventies or eighties, the deterministic genes are almost certainly not the story. Talk to the doctor if symptoms started unusually early or several relatives were affected young.

How heredity differs by type of dementia

Families ask about Alzheimer’s, but there are several dementias and they do not inherit the same way. My post on what causes the different types of dementia covers the conditions; here is the hereditary picture in general terms.

Type of dementia	Hereditary pattern	What it means for relatives
Late onset Alzheimer’s	Risk genes and family history raise odds; no single cause	Modestly higher risk; lifestyle and health still matter
Early onset familial Alzheimer’s	Rare, caused by a single inherited mutation	Each child of a carrier has about a one in two chance of inheriting it; genetic counseling advised
Vascular dementia	Not inherited directly; shares risk with heart disease, stroke, diabetes and high blood pressure	Family history of those conditions matters more than family history of dementia
Lewy body dementia	Mostly not inherited; rare familial cases	Low direct risk for relatives
Frontotemporal dementia	A meaningful share is familial through known genes	Worth asking the doctor about genetic counseling if more than one relative is affected
Huntington’s disease	Deterministic, single gene	Each child has a one in two chance; testing is available and is a personal decision

Mixed dementia, where Alzheimer’s changes and vascular damage occur together, is common in people over 80 and follows the risk factor pattern, not the single gene one.

Should you get a genetic test

For most families the honest answer is that a test for APOE will tell you about risk and not about fate, and it may change how you feel more than what you do. Doctors generally do not recommend APOE testing to predict Alzheimer’s in healthy people, because the result does not change the advice: protect your hearing, your heart and your sleep, stay active and stay social.

Testing is a different conversation when early onset or frontotemporal dementia runs through a family, or when a newer treatment for early Alzheimer’s requires knowing APOE status because of side effect risk. In those cases the test is done through a doctor with a genetic counselor on hand, and the counselor matters as much as the result. Mail order tests that report APOE status come without that support and have led to a lot of frightened phone calls in my office. If you take one, bring the result to your doctor before you draw any conclusions.

What changes risk that has nothing to do with genes

The encouraging news in published research is that a large share of dementia risk is tied to things people can influence. Studies suggest that hearing loss, high blood pressure, diabetes, smoking, heavy drinking, obesity, physical inactivity, depression, social isolation, head injury and air pollution each contribute, and that addressing them in midlife and later may delay or prevent a meaningful share of cases.

None of this is a guarantee and none of it is a cure. It is a reason to get the hearing aids, keep the blood pressure appointment and keep the Tuesday card game. I see the social piece every week in communities: the resident who joins the table at lunch tends to hold on to more than the one who eats alone. Ask your own doctor what applies to you.

Why families ask before a move, and what it changes

Adult children ask about heredity at the moment they are choosing a community for a parent because the decision makes the disease real. It changes nothing about the placement. A community admits a resident based on an assessment of needs, not on genes, and I choose a community based on how well it will handle the next two years, not on why the dementia happened.

It does change how I talk to the family about planning. My horizon runs 18 to 24 months past the move so a rising level of care is already in the plan, and a family that has just learned how dementia can unfold is usually ready to hear that. It also prompts the adult children to get their own paperwork in order. If watching a parent lose capacity teaches one thing, it is to sign a power of attorney and a health care proxy while you can, for yourself as well as for them. My post on the five legal documents every senior needs is the place to start, and an elder law attorney is the person to finish with.

What I look at when a parent has dementia, whatever the cause

The cause of the dementia matters to the doctor. The stage, the behaviors and the pace matter to me, because they decide which setting works. Across Long Island and Queens there are about 47 memory care programs, 42 of them inside larger assisted living communities and 5 free standing, and they are not interchangeable.

On the first call I ask about the diagnosis, where the person is in the course of the disease, what a typical day and a bad night look like, where the family wants to be and what the finances will carry. Then I pick the communities worth touring and we go together, where I watch staffing, food, how aides speak to residents and what the contract says about care level changes. My memory care guide lays out the three care types and the questions I ask in each building. How quickly things move is its own topic, and I wrote about it in how fast dementia progresses.

Practical steps for a family after a diagnosis

Whether or not the dementia runs in your family, the next steps are the same, and the order matters.

1. Get a complete workup from the doctor so treatable conditions that mimic dementia are ruled out. I explain them in can dementia be reversed.
2. Sign or update the power of attorney, health care proxy and will while your parent can still take part, with an elder law attorney.
3. Put the finances on one page: income, savings, insurance, the house, and what each will cover.
4. Decide who the point person is in the family and how decisions get made, especially if your parent has no insight into the illness.
5. Call me, and let us tour two or three memory care programs before there is a crisis, so the choice is made calmly.
6. Ask the doctor about genetic counseling only if symptoms started early or several relatives were affected young.

Families who do these six things in the first few months after a diagnosis have options. Families who wait for the hospital discharge planner to force the question usually have one.

Talk to me, at no cost to your family

Assisted Living Locators of Long Island helps families in Nassau, Suffolk and Queens find the right memory care, assisted living or independent living community, and the help is free to families; communities compensate the advisor when a family moves in. I hold a dementia care certification and I have toured more than 90 communities.

My office is at 42 Prospect Ave, Glen Cove, NY 11542. Reach out for a conversation about your parent and your family.

Questions readers ask

Read next

• Do People With Dementia Know They Have It? Anosognosia for Families
• Can Dementia Be Reversed? Conditions That Look Like Dementia but Are Treatable
• Assisted Living With Memory Care Under One Roof: How the Hybrid Communities Work