India, April 9 -- As people grow older, one of their biggest hopes is to stay independent, whether that means being able to stroll through the park, whip up a quick meal, or head out to meet friends without needing help. Staying active and self-reliant is often more important to them than anything else. Yet despite how common this goal is, there's still a lot we don't know about what actually causes disability in older adults or what leads to the loss of these abilities over time. (Also read: Poor knee health in older adults: 5 exercises to improve joint strength )

A new Yale study published in JAMA Network Open took a closer look at how illness and injury affect older adults, specifically, how long they're able to stay active versus how...