The number of Americans aged 90 and older has tripled in the past three decades and will quadruple again over the next four, according to the U.S. Census Bureau, and the majority of people in this age group have one or more disabilities. But medical studies typically seek volunteers with one—and only one—disease so that variables can be eliminated from research data.

“Those people don’t exist!” says geriatric medicine expert Leo M. Cooney Jr., M.D., Humana Professor of Medicine—at least not among the patients he treats. In other words, there is a rapidly growing segment of the population that health researchers have historically made a point of excluding from studies. But that is changing, and the Yale Program on Aging (POA), founded by Mary E. Tinetti, M.D., in 1991 and now one of the most respected research programs on health and aging in the U.S., has led the way.

The POA has developed research methodologies that take into account the multiple health issues that seniors typically face to examine how these problems interact and to develop evidence-based interventions that promote quality of life and independence.

“We have the opportunity of potentially solving some of the most vexing issues in our society,” says Thomas M. Gill, M.D., Humana Professor of Medicine, and current director of the POA and the affiliated Claude D. Pepper Older Americans Independence Center, which was launched at the School of Medicine in 1992.

“Rather than adapt our research questions to the available methodology, we really adapted the methodology to the clinical questions,” says Tinetti, the Gladys Phillips Crofoot Professor of Medicine and professor of epidemiology and investigative medicine.

The program is home to a team of biostatisticians sought after throughout the medical school for their ability to apply rigor to out-of-the-box questions. “We have one of the best biostatistics cores in the country,” says Cooney.

Tinetti has worked with this team to develop ways to explore complex issues in the lives of older people. Her work has focused on falls, an area that many researchers would have seen as hopelessly broad. Many physical factors play into falls, as do furniture arrangement, poor lighting, and other factors. But falls cause 95 percent of hip fractures and kill more than 20,000 elderly Americans a year, according to the Centers for Disease Control, so Tinetti saw falls as a major public health issue that was worth pursuing.

Tinetti’s research proved that falls, once thought an inevitable part of aging, could be predicted and prevented, and that fall-prevention programs offer significant health care savings.

Demonstrating the success and cost-effectiveness of interventions has been a hallmark of POA research, which has led to widespread adoption of the fall-prevention strategies Tinetti championed, and of strategies to prevent delirium during hospital stays, devised by former POA member Sharon Inouye, M.D., adjunct professor of internal medicine and assistant clinical professor of nursing.

“We have taken our research to the next step that a lot of researchers don’t,” says Tinetti. “Not a publication in a top journal or a presentation at a national meeting. The next step is working with the clinical community and the community at large.”

Tinetti’s work has received wide praise, and earned her a MacArthur Fellowship (or “Genius Grant”) in 2009. But she maintains that research on aging remains “unglamorous,” so the POA makes a point of aggressively recruiting medical students and young physicians for training. “We make major investments in young investigators,” and not all are geriatricians, says Gill, also professor of public health. The program works with doctors who specialize in cardiology, infectious disease, or any other areas that come into play in the health of older people. Increasingly, basic scientists are collaborating with clinical researchers.

The necessary element is that collaborators be “brave enough to embrace the complexity” of the field, says Gill, who was once a trainee in the program himself, working under Tinetti. He credits her with revealing this complexity—the “almost overwhelming” interrelationships among the health problems facing seniors. But complexity has its advantages, he adds, often leading to multiple strategies to help elderly patients stay independent. For example, though numerous factors contribute to falls, by addressing just a few of these causes, clinicians have been able to make great progress in their prevention.

Gill’s work focuses on disability in the elderly (also once thought to be part and parcel of aging) and how relatively simple interventions might slow or prevent it. He is the primary investigator at Yale for the Lifestyle Interventions and Independence for Elders (LIFE) study, a multi-site project funded primarily by the National Institutes of Health’s National Institute on Aging, in which researchers are examining how physical activity affects people who are sedentary and at risk of disabling illnesses and injuries.

When a patient named Richard (a pseudonym) first joined the LIFE study, he was recovering from hip surgery, and walking for 20 minutes was a challenge. “I was really out of shape,” he remembers.

Now, less than three years later, Richard arrives early for his twice-weekly sessions on a walking track so he can get in a full hour. “It’s definitely helped me,” says Richard, who at 83 reports that he’s healthy and takes long neighborhood walks on days he doesn’t report to the LIFE study.

If the intervention proves effective, it could be widely and easily adopted by existing facilities, such as senior centers or YMCAs. “This society generally and policymakers specifically are really looking for cost-effective interventions to decrease the rate of increase in the Medicare budget,” says Gill. Tinetti agrees, saying, “We spend an awful lot of health care dollars on things that don’t work.”

Cooney first became interested in geriatrics in 1969 at Boston City Hospital. “I started seeing older patients who I felt were not being very well cared for.” The level of disability in the elderly population has dropped since then, he says, and there is a growing awareness among physicians of the need to treat “people, not diseases.”

Tinetti believes that there is a hopeful trend of rejecting the idea that quality of life must decline sharply with age. “The baby boomers won’t stand for that,” she says.