Cambridge’s increasing affluence may threaten residents who want to continue living in the city after retirement, officials said at a roundtable discussion yesterday.

Clifford Cook, planning information manager for the Community Development Department, said that as Cambridge becomes more affluent, it becomes more difficult for elderly residents—who are often on fixed incomes—to afford rising rents and other costs.

Cook added that the city is becoming more socioeconomically diverse because the number of low-income residents—who often live in public housing—has remained constant, while higher-income individuals have steadily replaced middle-class residents.

“When we no longer have as many folks who are middle income in the community, it makes it that much harder to bridge that divide,” said Beth Rubenstein, the assistant city manager for community development.

Councillor Henrietta J. Davis said that because of the changing demographics, the city would need more assisted-living units and find ways to accommodate the elderly with better transportation and more accessible buildings.

Several people at the meeting said they were concerned about seniors whose incomes are too high for them to qualify for federal assistance, but too low for them to live comfortably in Cambridge, which has some of the highest real-estate prices in the country.

Davis and other councillors pointed out that while the number of housing units has steadily increased in the past 50 years, each unit accommodates fewer people. And with the demise of rent control in 1994, inflation-adjusted rents have increased substantially.

Councillors said they were surprised by other changes in the city’s demographics, such as the fact that it is becoming more racially diverse.

“I think these trends are really profound,” said Councillor Sam Seidel, who is an urban planner. “The city’s composition is changing. We’re now at one-third non-white.”

Some councillors were concerned to learn that 40 percent of the children under 18 in Cambridge speak a language other than English at home. But Ellen Semenoff, the assistant city manager for human resources, said that while Cambridge is becoming more diverse, with growing black and Asian populations, the city has few “linguistically-isolated” households.

—Staff writer Sarah J. Howland can be reached at showland@fas.harvard.edu.

—Staff writer Michelle L. Quach can be reached at mquach@fas.harvard.edu.