Justice Lab is a column that examines the science, social science and technology of criminal justice

Last year, Marielle Bolano, a student helping her professor research the health of aging inmates at a jail in San Francisco, asked one of them if he had trouble walking.

He laughed, telling her, “I can’t stand for more than 15 minutes...Sometimes walking hurts so much I get dizzy.” He also suffered from insomnia, regular falls, anxiety, and urinary incontinence. Bolano would later describe his health profile as “typical for a man in his eighth decade.” The man was 57.

For years, corrections officials have spoken of prisoners who appear far older than their actual age. In the early 1990s, a few officials suggested to the sociologist Ronald Aday that “the typical inmate in his fifties has a physical appearance of at least 10 years older.” That comment was cited widely by journalists and researchers, and a handful of mysteriously specific claims have floated around, saying prisoners over 50 have a health profile of people 11.5 years older.

Aday says no studies have proven that prisoners age at a specific rate compared to those on the outside. But a slow trickle of studies—including the one Bolano assisted with—have started to show that there is medical evidence behind the idea that at around age 50 prisoners start to contend with the health problems more often associated with people far older.

The question is particularly salient now as the federal Bureau of Prisons attempts to define who exactly counts as an “aging” prisoner. Across the country, laws passed a generation ago to increase sentences and limit parole have combined with the population bump of the baby boomer generation. Between 1992 and 2001, the number of state and federal inmates age 50 or older increased from 41,486 to 113,358.

State budgets have been hit hard as these prisoners get older and need treatment for serious diagnoses like cancer and heart disease (In 2012, Texas spent nearly $2 million on 10 particularly sick prisoners). Programs with names such as “medical parole” and “compassionate release” have allowed low-risk prisoners to get out early while shifting the cost burden to families or federal programs. But “once they reach that point, it’s kind of too late,” says KiDeuk Kim, a researcher at The Urban Institute who argues that prisons need to invest more in preventive medicine.

As researchers and corrections officials try to understand the dynamics of aging in prison, they are hampered by a lack of uniform definitions for terms such as “old,” “elderly,” “aging” and “geriatric.” When the Vera Institute surveyed all 50 state prison systems, they found that 15 states used age 50 as a cutoff for the definition of “older,” five used 55, four used 60, two used 65 and one used 70.

A 2004 study by the federal National Institute of Justice argued that 50 should be the cut-off age. The stress of staying safe behind bars, personal financial woes, drug or alcohol withdrawal, and a history of poor health care can speed up the aging process for inmates, the institute said.

Researchers have recently been trying to show more systematically that prisoners should be considered “old”—and therefore entitled to geriatric medical programs and the opportunity for release—at a younger age.

Most recent studies on the subject have found that prisoners in their 50s start showing signs of deteriorating health that those outside prison don’t see until significantly later. In 2007, three Pennsylvania researchers interviewed 51 male inmates in their state with an average age of 57.3 years and 33 men in the community with an average age of 72.2. They found that between the two groups, rates of high cholesterol, high blood pressure, poor vision, and arthritis suggested that the health of male inmates was comparable to men 15 years older.

Dr. Brie Williams, a professor of medicine at the University of California, San Francisco, worked on a 2012 survey of 247 male and female inmates at the San Francisco County Jail with an average age of 59. They reported having poor or fair health, chronic lung disease, and recent falls, at rates similar to people on the outside who are 71.7 years old.

Williams and other doctors have suggested categorizing prisoners not based on their chronological age but on other signs of health, including their ability to perform tasks, such as basic personal hygiene, or general health indicators, such as bone density or blood pressure.

This would help corrections officials steer past another problem: a group of prisoners, all the same age, might have wildly different health needs. Anecdotally, some prisoners have said that being in prison actually preserved their health.

“There is a small pocket of older adults doing better than you'd expect, because there are physically four walls around then,” Williams said. “Just like in the regular community, you have a few people in their 70s who can run a marathon. Age is just a number.”