Rich Americans and ones with private health insurance find five activities of daily living easier such as walking across a room, bathing, eating, dressing and getting in and out of bed, study found.
Especially troubling, though, was how the disadvantage for the poor snowballs over time, and determines when the elderly need to be institutionalised, said Virginia Richardson, co-author of the study and professor of social work at Ohio State University.
"The rich stay healthier, while the poor see steeper declines in their health as they age," Richardson said.
This study is one of the few that have linked socioeconomic status - which includes income and assets - and health insurance on people's physical functioning over an extended period of time, according to Richardson.
The researchers used data from the Health and Retirement Study, run by the University of Michigan, which followed Americans over 50 years of age over the course of 12 years, from 1994 to 2006. Data was collected every two years. For this study, Richardson and Kim used data on 6,519 participants.
In 1994, when data was first collected, the researchers found that those with higher income and assets had better functioning.
"The more income and assets you have, the slower your health decline will be," she said.
Those who had private health insurance also reported fewer problems with physical functioning than those who didn't at the beginning of the study.
The study has been published in the journal Health.