NASHVILLE (AP) — A recent study by a Vanderbilt University researcher shows that for every year a person spends behind bars, life expectancy decreases two years.

Evelyn Patterson is assistant professor of sociology at Vanderbilt. Her study, published online last month by the American Journal of Public Health, looks at New York parolees released between 1989 and 1993.

The results showed a 15.6 percent increase in the odds of death for parolees compared to people who had never been to prison, which translates to a two-year decline in life expectancy for every year served inside prison.

However, Patterson said the study did reveal a small bright spot. If a prisoner serves out parole without returning to prison, the study shows he eventually gains the years back to his lifespan lost during his prison stay.