En español | Like everyone else who's jumped the fence into "later middle age," I have senior moments. Words and names flow to the tip of my tongue and stop. I can't add and subtract in my head as readily as I used to. We may grow wiser with years, thanks to the lessons we reap from experience, but we aren't as quick. A 2009 study on financial decision-making called "Age of Reason" put our mental sweet spot — knowledge plus agility — at an average age of (are you ready?) 53.

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In short, preparing for retirement is just part of the picture. You also have to prepare for the risk that, at some point, your thinking won't be as clear as it is today. Some of us will stay sharp (or sharp enough) into our 90s. Others will suffer declines that make us vulnerable to serious money errors or even fraud. Investment advisers face the same question as do our family and friends. What should they do if they think we're losing our grip on financial decisions?

Don’t be afraid to ask for help managing your money. — Photo by Getty Images

In a new study, called "Protecting Older Investors: The Challenge of Diminished Capacity," AARP surveyed the safeguards that financial firms put in place. Most said they'd stop making investment recommendations if they suspected a client was losing track, says Naomi Karp, who headed the research team. Some said they'd wait for clarification if they had concerns before following a client's instructions to buy or sell.

The tough part is knowing when to sound the alarm — not only for advisers but for you and me. Financial planner Linda Patchett of Chapel Hill, N.C., gets it right when she says, "Within each person rages the tension between maintaining independence and selfhood and recognizing deficits." Age 60, she says, is "a very good time to bring the issues of aging into sharper focus."

Four steps to take:

1. Get your documents together, starting with a durable power of attorney (POA). It lets someone make financial decisions for you if you cannot. But POAs can be powerful documents in the wrong hands, so talk over your wishes carefully with the agent you choose. Your document dump should include an up-to-date will, living will, health care power of attorney and current beneficiary forms for an individual retirement account and other assets. People in the initial stages of dementia might consider a do-not-resuscitate order, to prevent future overtreatment by doctors at a time when they can't choose, says Brentwood, Tenn., planner Mark Nickell.

Don't forget the digital documents. When a client of Patchett's threw out her husband's computer after his death, all of his passwords and payment records went with it. Reconstructing them was expensive.

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