WASHINGTON - The United States' population aged 90 and above nearly tripled over the past three decades, reaching 1.9 million in 2010, a report released Thursday by the US Census Bureau said.

This population now comprises 4.7 percent of the older population (age 65 and older) in the country, as compared with only 2.8 percent in 1980, the report said.

The report, supported by the National Institute on Aging, estimated that this group of people will quadruple over the next four decades because of increasing life expectancy. By 2050, this group will likely make up 10 percent of the older population.

The majority of people aged 90 and older report having one or more disabilities, living alone or in a nursing home and having graduated from high school.

Also, people in this age group are more likely to be women and to have higher widowhood, poverty and disability rates than people just under this age cutoff.

According to Census Bureau demographer Wan He, traditionally, the cutoff age for what is considered the 'oldest old' in the United States has been 85. He called for more attention to be paid to this group of people.

The report said an older person's likelihood of living in a nursing home increases sharply with age.

While about only 1 percent of people in their upper 60s and 3 percent in their upper 70s were nursing home residents, the proportion rose to about 20 percent for those in their lower 90s, more than 30 percent for people in their upper 90s, and nearly 40 percent for centenarians.