BOSTON (Reuters) - Provo, Utah, and Sioux Falls, South Dakota came out on top in a new index of the best U.S. communities to live for senior citizens, based on factors that promote successful and healthy aging.

The Milken Institute's "Best Cities for Successful Aging" study, released on Tuesday, took into account 78 factors that affect senior citizens' quality of life including affordability, safety, health, financial security, and transportation.

Job prospects were among the criteria as well, reflecting a "new economic and social reality" that many seniors want to, or will be forced to, continue to work during their so-called retirement years.

Out of the 100 largest metropolitan areas in the United States, Provo, the home of Brigham Young University, scored top marks for its healthy lifestyle, small-business growth, and numerous medical centers.

Sioux Falls ranked first among 259 smaller cities because of its senior-friendly programs, such as its Medicare and state funding for seniors, and booming economy, the Milken Institute said.

Other large cities termed good for seniors include Madison, Wisconsin, Omaha, Nebraska and Boston while seniors looking for smaller cities to call home were directed to Iowa City, Iowa, Bismarck, North Dakota, and Columbia, Missouri.

"The question wasn't 'what's the best place to retire,' but what areas have the best amenities in the future," said Ross DeVol, chief research officer at the Milken Institute and co-author of the study.

DeVol noted that the presence of universities boosted the rankings of some cities. Not only do they offer their educational services to seniors, but residents often benefit from their health services, including specialized forms of health care.

There was "virtually a complete absence" of cities in the Sunbelt region of the southern and southwest United States, which DeVol said was surprising given its popularity with retirees, but was likely because of poor employment. Continued...