Elderly assisted living facilities are disproportionally located in more affluent areas, with Massachusetts lagging far behind other states in terms of the number of assisted living units available, according to a recent Harvard Medical School study.

After calculating the ratio of number of assisted living units per thousand of people over 65 years of age for every state, researchers found that the locations of the facilities showed a strong connection to the education levels, property values, and ethnic makeups of the areas. More facilities were found to be situated in areas with a lower proportion of black and Hispanic residents—a correlation researchers said they found “disconcerting."

Since Massachusetts is comparatively affluent, the fact that most of the state’s counties fell below the national average ratio came as a surprise to the researchers, they said.

“It appears that there are unmeasured factors at play, such as property taxes or local regulations, that influence our measure for the distribution of assisted living facilities,” said David C. Grabowski, associate professor of health care policy at HMS and the paper’s co-author.

In a broader sense, the study's conclusions raise potentially troubling issues regarding the nation’s longterm care for the elderly, according to Grabowski.

In contrast to nursing homes, which are primarily funded by Medicaid and Medicare, assisted living homes have traditionally been financed privately. As a result, “it makes sense” that they would naturally be found in areas of higher income, said David G. Stevenson, assistant professor of health policy at HMS and lead author of the paper.

“This is not a criticism of assisted living,” Stevenson said of the study's results. “It’s a natural byproduct of how they’re financed, but it does raise a number of important issues.”

Two issues could stem from the uneven distribution of assisted living units, according to Stevenson: capacity and efficient use of state funds. Residents of rural or lower income areas may face difficulty accessing assisted living units and be forced to relocate, and since nursing homes are generally more expensive for the state, this may mean that more money is used to pay for individuals living in nursing homes who could be better—and more inexpensively—served in assisted living facilities.

The study also raises broader questions of equality and issues of financing elderly care, according to Grabowski.

Currently, assisted living is not covered by most states and is paid out-of-pocket by individuals. Grabowski said the system “accentuates a two-tiered elderly health care,” in which people from lower income communities live in Medicaid-financed nursing homes,  while those who can afford the costs choose assisted living—the favored type of care.

“There are many reasons why we don’t want to create Medicaid mills and segregate our Medicaid populations," Grabowski said. "Rather, we should opt for a more integrated model of care."

Although the study suggests that residents of rural and low income areas may have difficulty accessing these facilities, Paul Williams—the senior director of government relations at Assisted Living Federation of America—said such issues do not exist.

“We never get calls about lack of beds or space, and people who look for [assisted living] aren’t finding them only in places with rich people or big cities,” Wiliams said, pointing to homes in Wisconsin and Florida with only four or five beds as examples of care that “better fit the needs of small communities” that the study may not have considered.

The study—funded by the Robert Wood Johnson Foundation—was published Tuesday in the journal Health Affairs.

—Staff writer Helen X. Yang can be reached at hxyang@fas.harvard.edu.