D.C. Council Member Vincent C. Gray will convene a hearing Friday on legislation that would affect which assisted living facilities in the city can care for patients with Alzheimer’s and other dementia-related illnesses. (Jahi Chikwendiu/The Washington Post)

Meredith Lair and her family had a plan. After watching her grandmother and then her aunt battle Alzheimer’s, Lair knew what she had to do when she noticed symptoms of the deadly disease in her mother.

Her parents spent their life savings moving from Ohio to Washington, where they could be closer to their daughter and live in a retirement community that would afford Lair’s mother a range of care options as her suspected illness progressed.

But now Lair is worried that a D.C. Council bill might leave her mother with nowhere to go.

The legislation, which the council’s health committee is scheduled to discuss in a Friday hearing, will update 18-year-old laws regulating the District’s ­assisted-living residences — something most everyone agrees needs to happen.

But tucked into the bill is one sentence that would prohibit those facilities from admitting anyone who “is or has ever been diagnosed with moderate to severe dementia, or requires hospice care.”

That could affect hundreds of city residents struggling with dementia.

“This really detonated a bomb in a lot of people’s lives,” Lair said.

If her mother isn’t able to get into an assisted-living residence, Lair doesn’t know what they’ll do. The only other options — putting her mother in a nursing home or paying for in-home care — would be too costly, she said.

“This looms very large and is very scary,” Lair said.

About 600 people live in the city’s 12 assisted-living residences, according to LeadingAge D.C., a local chapter of an association of nonprofit organizations that care for the elderly. Nationally, it’s estimated that 50 percent of people in assisted living have dementia.

“It is causing a lot of seniors and family members in the District great concern,” said Christy Kramer, the director of Leading­Age D.C.

The bill would not displace those with dementia or in need of hospice care who are already in assisted-living facilities.

But Laurence Barrett, whose wife has Alzheimer’s, worries what will happen after current patients die and new patients with dementia are not allowed admission.

“Virtually everyone I know is up in arms about this; they can’t figure out the rationale,” Barrett said.

Council member Vincent C. Gray (D-Ward 7), the lead sponsor of the bill and chair of the council’s health committee, did not comment on why the specific provision was inserted, but he said he takes public feedback “very seriously” and would listen to residents’ concerns as the council considers possible amendments. All 13 council members are sponsors of the legislation.

Kate Sullivan Hare, executive director of the Long Term Care Quality Alliance, the group that crafted and advocated for the bill, said the line came from “very real experiences of residents witnessing the horrible effects of late-stage Alzheimer’s disease.”

“It was affecting their own well-being because they were so upset at how their neighbors were suffering,” she said.

However, Sullivan Hare said her group did not intend to bar dementia and hospice patients from all assisted-living residences.

Rather, her group wants dementia patients limited to facilities with dedicated “memory care units.” These units, usually secure and separated from the rest of a facility, are best equipped to treat patients with moderate to severe dementia, Sullivan Hare said.

She said she would support an amendment clarifying that facilities with specialized units would still be allowed to admit patients with dementia.

Her mother spent seven years in a D.C. assisted-living facility, and Sullivan Hare said she understands the uproar — everyone wants “someplace safe” for their family members to go when they need additional care.

But across the country, most people with dementia do not live in memory-care units, said Sheryl Zimmerman, a professor and assisted-living expert at University of North Carolina at Chapel Hill. “Also, the care in those units isn’t always better,” she said.

What matters is quality of care, not the unit in which the patient receives it, she said.

Some say the best, most humane way to provide that care is to give patients with dementia the option of living among residents who are not cognitively impaired.

“The question is, do you believe you should segregate people with Alzheimer’s disease from the general population, and we don’t believe you should do that,” said Carter Harrison, the Alzheimer’s Association’s head of state and local policy in the Washington metro area. ­“Memory-care units provide an important part of the care continuum; however, that should not be the only option available.”

The Alzheimer’s Association and LeadingAge D.C. are two of the organizations paying close attention to the legislation. There are several provisions in it they like — among them, higher standards of training, especially for staffers who deal with dementia patients, and measures intended to establish and ensure residents’ rights.

“The D.C. Council is looking to do something we’ve needed to do for a long time,” said Kramer, adding that new regulations are “long overdue.”

The council won’t vote on the bill at the Friday hearing, which is scheduled for 10 a.m. in the Wilson Building, but about 50 people have signed up to testify.

Lair said she realizes that parts of the bill may bring improvements, but after reading the provision that would affect her mother’s care, she said she no longer trusts the council to catch another such oversight.

“I want experts to read it, I want lawyers to read it, so that when it’s approved it doesn’t wreak havoc in people’s lives — and that’s a fair thing to expect from our elected officials,” she said. “I am losing faith in the process.”