When Thomas Gill compares the human body to a car running low on fuel, he's not speaking metaphorically. A new Yale School of Medicine study suggests that maintaining what researchers call "intrinsic capacity"—the full range of mental, physical, sensory, and psychological abilities—may be one of the most important ways older adults can preserve their independence. And the findings, published in The Lancet Healthy Longevity, offer a surprisingly long runway for intervention.
The research tracked 746 adults aged 70 and older living in South Central Connecticut over a 20-year period, following them from health to the end of life. What they discovered challenges assumptions about aging: the connection between overall capacity and disability becomes stronger, not weaker, as people approach death. Specifically, the study found that higher intrinsic capacity was linked to lower odds of disability beginning around 14 years before death—and that link only grew stronger with time.
"Clinically, one can think of intrinsic capacity as a gas tank that drains as we age," said Gill, the Humana Foundation Professor of Medicine in geriatrics at Yale and senior author of the study. "By intervening to bolster reserves, we can preserve that fuel and avert disability."
Olivia Malkowski, a postdoctoral associate in Yale's Department of Internal Medicine and the study's first author, said the research represents a shift in how scientists think about healthy aging. Rather than focusing solely on physical health, measuring intrinsic capacity captures what older adults themselves say matters most: the ability to think clearly, move freely, hear and see well, and maintain emotional balance.
"By measuring intrinsic capacity, we're not just looking at physical health," Malkowski explained. "We're looking at other things that are important to older adults, such as mental, cognitive and sensory health, which are sometimes overlooked when we attempt to measure healthy aging."
To conduct the analysis, the researchers used time-varying effect modeling—a statistical method that allowed them to watch how the relationship between capacity and disability shifted month by month in the years before death. Traditional approaches assume this relationship stays constant over time, which can mask important changes.
Malkowski cautions that the findings are early evidence, not yet a clinical roadmap. But she sees clear potential in what the data suggests: regular checkups that track not just blood pressure and weight, but also walking speed, memory, mood, and sensory health could help identify people who might benefit from early support. The goal would be to help older adults stay independent longer—able to shop for groceries, prepare meals, manage their finances, and move through the world on their own terms.
"This is early evidence that monitoring things like walking speed and memory as part of routine care could be useful for developing early interventions to help older adults preserve their independence and quality of life," Malkowski said.