Late one night, the phone rings. It’s my mom. I brace myself and pick up.

“The Baltimore police just called,” she says. “Your brother is in jail!”

I know — well, I’m pretty certain — that my brother, who lives hundreds of miles from Baltimore and is a ­law-abiding family man, isn’t in jail, but that doesn’t really matter. Right now, the point is to calm my mom down.

So, I tell my mom that I’ll figure it out and get back to her. I take a deep breath and send a quick text to my brother, who confirms he’s nowhere near Baltimore or a jail cell and promises to call her right away. I call my mom back a few minutes later, and on this night, the calls do the trick. Everything is okay again, for the moment.

In recent months, I’ve gotten quite a few perplexing and frantic calls as my kind, intelligent, 91-year-old mom struggles with Alzheimer’s disease.

Unfortunately, she is one of many people whose descent into dementia has been twinned with a surge of anxious thoughts. Anxiety isn’t a cognitive issue per se, but it’s definitely a symptom that makes life much harder for caregiver and patient alike. Just imagine being stuck in your worst worries.

Making it tougher is the strangeness of what my mother is anxious about — my brother being in jail or her needing to cancel an event, get to a meeting or get home (when she’s already home). It happens in person, too. Something is upsetting her, and she’s telling me about it, but I can’t get what it is she’s worried about. Quickly, her anxiety becomes my anxiety, too.

Some 80 percent of people with dementia experience anxiety and agitation at some point, said Lea Grinberg, a neuropathologist whose lab at the University of California at San Francisco studies brain aging and associated disorders. She is exploring whether anxiety and depression could sometimes be early indicators of cognitive disorders.

“Anxiety may be part of the disease process,” she said.

Anxiety can be a byproduct of the transition from the normal aging brain to cognitive impairment, some experts said. Understandably, it can also be triggered when people with dementia experience stressful events associated with changing bodies and minds, such as having to move from their home of many years. And, then there are people such as my mom, who has always been a worrier but had also been a high-functioning person who managed to cope with her worries and get on with her life. After Alzheimer’s entered the picture, that has been less and less possible.

People with Alzheimer’s have brains that are “processing differently and processing more slowly,” said Ruth Drew, the director of Information and Support Services at the Alzheimer’s Association. It’s easy for them to feel overwhelmed and overstimulated, and cascading worries can be set off just by feeling uncomfortable — being tired or hungry, having the sun in their eyes, feeling cold. But they may be unable to figure out how to articulate or solve a problem, Drew said.

Many can be disoriented. They look at their living space and think something is off. In my mom’s case, one of the first warning signs that things were changing was her repeated concern that someone had moved all of her belongings into a “new” room at her assisted-living facility. The room, she marveled, looked exactly like her old room. That it was her old room didn’t occur to her.

For caregivers, identifying patients’ anxiety triggers can be helpful.

Even healthy “worriers,” which my mom once was, tend toward “catastrophic thoughts,” Drew said. These are people who fear, for instance, that the son or daughter who hasn’t called is hurt or that their headache is a brain tumor. They shake it off when their brains still work properly, but add dementia, and they “can’t turn that off,” Drew said. Old coping mechanisms no longer work.

In hindsight, I realize that my mother’s Baltimore police panic hit as I was about to go out of town. The next time I travel, I’ve decided not to tell my mom. My brother and other family members will know, and her caregivers will, as well, but I’ll simply call my mom every day I’m away as if I’m calling from home.

On a positive note, Drew and others gave me credit for not telling my mom the police story was absurd but simply accepting it — taking it seriously but not escalating the situation.

Experts also advise adhering as closely as possible to their loved one’s schedule — something I’m paying more attention to after a disastrous doctor’s appointment, which I scheduled early so that I could take my mother to the physician and get to work on time.

The stress of getting her up and out early was clearly too much. Even though we were going to a familiar destination, my mom was visibly scared and confused, moaning repeatedly and crying, at times, because she feared something terrible was about to happen to her. I shifted her most recent doctor’s appointment to midmorning, and things went better.

Ronald Petersen, director of the Mayo Clinic’s Alzheimer’s disease Research Center, recommends playing a person’s favorite music and using other behavioral approaches to distract them. He also advises against trying to convince a person with dementia that they’re worrying about something that isn’t real. Opt for distraction over confrontation, he said.

Use “therapeutic fibs,” Petersen said. “It’s calming. You’re not deceiving anybody . . . The person cannot process the information, so you just go along with it. Don’t elevate the tension state with argument.”

Medication is a last resort when other efforts have failed or the person is in danger because of their symptoms, he said.

Jessica Bryan of Chapel Hill, N.C., runs several Alzheimer’s caregiver groups. Bryan, who cared for her parents during their progression through Alzheimer’s, has written four books on Alzheimer’s and caregiving, and blogs about her experiences. She is one of many authors whose work is featured at the AlzAuthors website, another resource for caregivers and people with dementia.

Bryan makes clear that the best tools for dealing with Alzheimer’s and dementia are empathy, flexibility and humor.

“All you can do is to understand and not fight it,” Bryan said. “Any form of yes keeps the doors open. You want to keep [a loved one] calm and happy and comfortable, and you don’t want to put them in harm’s way, and agitation can certainly put them in harm’s way.”

The Alzheimer’s Association operates a 24/7 helpline (800-272-3900), which receives about 300,000 calls a year and sometimes 1,000 calls in a day. Drew, who oversees the helpline, recommends that anyone with questions or concerns should call it.

“Dealing with dementia disease is difficult . . . No one should do this alone,” she said. “No one has to.”