PHILADELPHIA — If current trends continue, the number of aging homeless people will more than double in three major metropolitan areas, straining social and medical services, a report released this week concluded. It said that improvements in housing plus services aimed at preventing medical crises could sometimes save cities money.

The report was the work of researchers from several universities, including the University of Pennsylvania and the University of Delaware and was funded by four foundations. Data from New York, Boston, and Los Angeles County were analyzed.

Philadelphia’s homeless shelters also are struggling with an influx of older homeless people who have complex medical problems the shelters are not designed and staffed to handle. The city is working with area hospitals to provide better transitional care for homeless patients who no longer need hospital treatment but are too sick to live safely in most city shelters.

The report said the coming boom in aging homeless people stems from younger, less educated baby boomers who faced economic challenges in their youth: falling wages and rising housing costs. A disproportionate number wound up homeless, an effect that has persisted for decades.

Now in their 50s and 60s, they are biologically older than most people their age and already facing the medical problems of aging.

The report projected that the number of homeless people 65 and up will grow from 570 in 2017 to 1,560 in Boston by 2030, from a little above 5,000 to 13,900 in Los Angeles, and from 2,600 to 6,900 in New York.

The national population of people 65 or older experiencing homelessness is estimated to grow from 40,000 to 106,000 by 2030. The predicted spike is based on 30 years of existing census data.

New York spends an average of $25,000 on homeless people age 55 to 59, a figure that rises to more than $28,000 in people aged 70 and up. That includes the cost of shelter, emergency department visits, inpatient hospitalization, and nursing-home stays. Costs hovered around $20,000 in the other cities.

The researchers said the cities likely could save money, especially in the oldest, sickest group, by helping older homeless people find permanent housing and providing them with adequate medical and social support. They estimated that costs would rise in Boston, but that New York and Los Angeles County could save $20 million to $33 million a year by providing more housing and medical services.