While many people associate extreme old age with failing health, new research suggests that many centenarians live independent, healthy lives.

Danish researchers assessed the health, mental capacity and independence of Danes in their 90s over the 10-year run-up to their 100th birthdays. Although only 166 of the original 2,300 subject survived long enough to reach the century mark, researchers made an interesting discovery: The percentage of those able to take care of themselves in their early 90s was roughly the same as those able to take care of themselves into their 100s. A total of 37% of participants maintained an independent lifestyle at the start of the survey and 33% continued to do so at the end of it.

Because of the independence of the super-elderly, researchers say that a boom in this population might not have a major impact on healthcare expenditures. Findings appear in the August 18-22 issue of the Proceedings of the National Academy of Sciences.