The number of five-star nursing homes in the Philadelphia region fell by 20 percent, from 74 to 59, under a modified regimen for nursing-home ratings, federal data released Wednesday show.

The number of one-star facilities in the eight-county region, which has a total of 236 nursing homes, jumped 58 percent, from 24 to 38. One of those was the Delaware County-owned Fair Acres Geriatric Center, the largest nursing home in the region by far, which saw its rating fall from 4 to 1.

The latest rating of the nation’s 15,564 nursing facilities, easily available to consumers on Medicare’s Nursing Home Compare website, uses a new, uniform inspection methodology, includes new quality measures, and places a greater emphasis on the presence of registered nurses.

With about a million people aged 65 and older, Philadelphia ranks fifth among the country’s largest metro areas in terms of an aging population, according to the most recent census data.

The federal Centers for Medicare and Medicaid Services combine three separate ratings, based on health inspections by state officials, staffing levels now reported electronically through facilities’ payroll systems, and mostly self-reported quality measures, into one overall rating.

Since February 2018, the health inspection rating used on the Nursing Home Compare website had been frozen after implementation of a new survey process for long-term care facilities. That way, the health inspection scores available to the public would be based on the same process for all facilities.

“Ending the freeze is critical for consumers,” federal regulators said last month. “In April, they will be able to see the most up-to-date status of a facilities compliance, which is a very strong reflection of a facility’s ability to improve and protect a resident’s health and safety.”

Factors other than changes in the survey methodology, such as incidents involving negligence or other instances of faulty care during the period of the freeze, could also affect ratings.

For example, the overall and health inspection ratings for the nursing home at Cathedral Village, a continuing-care retirement community, fell sharply. Herbert R. McMaster Sr., the father of former national security adviser H.R. McMaster Jr., died there last April after falling five times during a four-day stay at the facility in Upper Roxborough.