A report released this week shows that Vermont has the second-highest health care spending per inmate in the U.S., and state data show those costs continue to grow.

States are legally obligated to cover the health care costs for inmates and, according to the report, the median cost per inmate nationwide rose 13 percent from 2011 to 2007, but peaked in most states prior to 2011.

That was not the case in Vermont where per-inmate health spending grew 17 percent during that period from $10,092 to $11,761. Only California spent more per inmate at $14,945 in 2011, according to the report, which was sponsored by the Pew Charitable Trusts.

Vermont paid its inmate health services contractor $18.7 million in fiscal year 2013, or $1.2 million more than FY 2011, according to state figures. The Pew report covers 2007-2011.

Aging prison populations, the prevalence of chronic conditions - including mental illness - and transportation and staffing for health services are among the primary factors the report identifies for the growth in spending.

Those are all problems that challenge Vermont's Department of Corrections, said Dee Burroughs-Biron, the department's director of health services, but keeping inmates healthy in prison can have a positive effect when they're released.

Vermont has the second-highest rate of inmates over age 55, according to the Pew report, and the state's inmate population continues to age, state data shows. Prisoners age 55 and older with chronic and terminal illnesses are on average two to three times more expensive to care for than other inmates.

Mental health and other chronic conditions make up the bulk of prisoner health services, the most recent figures from corrections show. Thirty-two percent of inmate sick-call requests were related to a chronic physical illness and 18 percent were related to mental illness in FY 2013.

Forty-four percent of male inmates and 73 percent of female inmates in Vermont required mental health services, according to a point-in-time census from June 2013.

Vermont's five-year contract with Tennessee-based Correct Care Solutions LLC ends this year, and a new request for proposals calls for potential vendors to include greater substance abuse services in their bids. A contract is expected to be awarded at the end of the month.