The neurologist uses careful words: mild, early, still very functional. Your father nods. On the drive home he says he feels relieved, because it could have been worse. Nobody in the car says what everyone is thinking: he has never signed a power of attorney, his will is from 1998, and it names a wife he divorced. Over the next few months the family will keep telling each other there's time. That isn't exactly a lie. But the time is being spent whether anyone counts it or not.

This article is about that stretch of time. A dementia diagnosis doesn't take away a person's legal right to plan their estate. In the early stages most people can still sign a valid will, a durable power of attorney, and a healthcare directive. What closes the window isn't the diagnosis. It's waiting, and families have strong psychological reasons to wait.

Capacity is not a switch

Most people picture mental capacity as a light switch, on or off. The law works differently, and that difference is the most useful thing to understand here.

Capacity is task-specific. The question is never whether someone is competent in general. It's whether they're competent to do this particular thing at this particular moment. Different documents carry different thresholds.

For a will, most U.S. states use some version of a test that traces back to an 1870 English case, Banks v. Goodfellow. Roughly, the person has to understand that they're making a will, know in general terms what they own, recognize who their natural heirs are (spouse, children, close family), and understand how those pieces fit into a plan. They don't have to remember what they ate for breakfast. They don't have to manage their own checkbook.

That bar is lower than many families expect. In many states it's lower than the standard for signing a contract, and some states treat a power of attorney more like a contract. So there can be a period when someone can still validly sign a will but their ability to sign other documents is getting weaker. The law also recognizes lucid intervals: a person whose cognition fluctuates can make a valid will during a clear stretch.

The good news is that a diagnosis is not a deadline. The bad news is that nobody can see where the real deadline is, and it arrives on its own schedule.

Why families wait anyway

If the window is real and narrowing, why do so many families wait until it's gone? The reasons are deeply human, and naming them is the first step past them.

Anosognosia. Many people with Alzheimer's and related conditions have reduced awareness of their own impairment. This is a neurological symptom, not stubbornness or denial in the everyday sense. Damage to the brain can affect the systems a person uses to monitor themselves. When your mother insists she's fine, she may honestly believe it. Asking her to "get her affairs in order" sounds to her like an accusation of something she doesn't experience.

Money skills slip early and quietly. Researchers who study financial capacity, notably Daniel Marson and colleagues at the University of Alabama at Birmingham, have found that complex financial skills like managing bank statements, spotting a bad deal, and paying bills accurately can start to decline in mild cognitive impairment, sometimes before a formal dementia diagnosis. This is also the stage when people are most exposed to scams and to pressure from people close to them. The person is at their most vulnerable just when everyone feels the least urgency.

The hope trap. Any conversation about incapacity asks the family to picture a future they're desperate to avoid. Avoiding that picture feels like loyalty. Psychologists describe a related pattern called present bias: we discount costs that sit in the future, especially vague, emotionally painful ones. "We'll deal with it when it gets worse" feels kind. In practice it hands the decision to a probate court.

Fear of the role reversal. For adult children, raising the subject can feel like taking their parent's place as the adult in the room. Many would rather say nothing than be the one to make that shift visible.

What happens if the window closes

If someone loses capacity without a durable power of attorney, nobody automatically has legal authority over their finances. In most cases that includes spouses for accounts held only in the other person's name, and it includes adult children. Usually the family has to petition a court for guardianship or conservatorship (the term depends on the state). That process typically involves filing fees, attorney fees, medical evaluations, a court hearing, and often continuing reports and court oversight afterward. The person you love becomes a respondent in a legal case about their own competence.

An outdated will is also a problem. If the 1998 will still names the ex-wife, what happens depends on state law. Many states automatically revoke provisions for an ex-spouse after divorce, but not all do, and the rules for retirement accounts and insurance policies can differ. If capacity is gone, nobody can fix it.

The documents that would have prevented all of this take a few hours to sign. The difficulty was never the paperwork. It was the conversation.

Signing in a way that holds up

When someone with a known diagnosis signs estate documents, the risk shifts from can they sign? to will someone challenge it later? Wills signed after a dementia diagnosis attract challenges, especially when the new plan differs from an old one or favors a caregiver. Two legal theories usually come up: lack of capacity and undue influence, meaning someone in a position of trust overpowered the person's free will.

You can't remove the risk of a challenge, but you can make one much harder to win:

  • Use an attorney, not a template. An estate attorney who meets privately with the client, asks open questions, and keeps notes becomes a credible witness to capacity.
  • Get a contemporaneous capacity assessment. A letter from the treating physician, or a formal evaluation close to the signing date, documents the person's state of mind when it mattered.
  • Keep beneficiaries out of the room. The child who stands to gain shouldn't drive to the meeting, sit in on it, or choose the lawyer if it can be avoided. Distance is evidence.
  • Let the plan be explainable. A plan that follows the person's long-standing values, or that comes with their own explanation for a change, is far harder to attack than an unexplained reversal.

Your next moves

  • Within the next week, find out which documents exist and how old they are. Write down the date of the most recent will, any durable power of attorney for finances, any healthcare proxy or advance directive, and whether there's a trust. If you can't find them, that counts as an answer too.
  • Ask the treating physician one specific question at the next appointment: "Would you be willing to document their capacity to make legal and financial decisions if we schedule an attorney meeting soon?" Write down the answer, and ask how they'd want to do it.
  • Book an elder-law or estate attorney consultation within 30 days, not "when things settle." When you call, mention the diagnosis so the attorney can plan the meeting around capacity documentation.
  • Pick a time of day, not just a date. Many people with dementia are clearest in the morning and more confused late in the day, a pattern often called sundowning. Schedule signings and hard conversations for the person's best hours.
  • Open the conversation by asking about what they want, not what they're losing. Try: "If you couldn't tell the bank or the doctor what you wanted, who would you trust to speak for you?" Asking who they trust is easier to hear than talking about decline, and it keeps them in charge of their own life.

The kindest thing is to go early

There's a version of this story where the family waits, out of love, until the decision is taken from all of them. There's another version where everyone has a hard conversation in the second month, while the person can still make their own choices. That version is the one that respects them.

If your family is in that window now, it helps to see everything in one place: which documents exist, who's been named, and what's missing. Heirloom gives you a clear view of a whole estate plan, so the conversation can start from facts instead of guesses about what's in a drawer. Whether or not you use it, start this month. You can explore it at heirloom.lumenlabs.works.