The oldest of the old are living even longer, a new report shows.

In recent years, the death rate among American centenarians — people who have lived to age 100 or older — has decreased, dropping 14 percent for women and 20 percent for men from 2008 to 2014, according to the report, from the Centers for Disease Control and Prevention.

In other words, "the risk of dying for centenarians decreased" over this period, study author Dr. Jiaquan Xu, of the CDC's National Center for Health Statistics, told Live Science.

The leading causes of death in this age group are also changing.

In 2000, the top five causes of death for centenarians were heart disease, stroke, influenza and pneumonia (the two conditions are grouped together), cancer and Alzheimer's disease. But by 2014, the death rate from Alzheimer's for this age group had more than doubled — increasing from 3.8 percent to 8.5 percent — making the progressive brain disease the second leading cause of death for centenarians.

One reason for the rise in deaths from Alzheimer's disease in this group may be that developing this condition remains possible even after people beat the odds of dying from other diseases such as cancer, said Holly Prigerson, a professor in geriatrics at Weill Cornell Medical College in New York.

"People who are physically fit enough to survive over 100 years ultimately succumb to diseases afflicting the mind and cognitive dysfunction," said Prigerson, who was not involved in the report. "In other words, it appears that their minds give out before their bodies do." [Extending Life: 7 Ways to Live Past 100]

On the other hand, the death rate from influenza and pneumonia was nearly halved during the study period, dropping from 7.4 percent in 2000 to 4.1 percent in 2014. That pushed influenza and pneumonia from the third leading cause of death to the fifth, the report said.

Overall, the total number of Americans living to age 100 or older is going up. In 2014, there were 72,197 U.S. centenarians, compared to 50,281 centenarians in 2000. But because this population is getting larger, the number of deaths in this group is also increasing — 18,434 centenarians died in 2000, whereas 25,914 centenarians died in 2014, the report said.

Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.