Being a cop in crime-plagued Detroit is already dangerous enough, but now there's proof that walking a police beat in the city Forbes just dubbed "the most miserable city in the United States" also shortens the lives of the city's men and women in blue.

In a first-of-its-kind study of retirement and life expectancy of a city's police and non-police workers, scholars from Detroit's Wayne State University and Milwaukee's University of Wisconsin found that Detroit police die an average of six years younger than other retired city workers.

While they offer no medical reason, the authors blame stress on the job, a loss of lifestyle and a surge in alcoholism and smoking for the shocking premature death rate. They also blame life as a Detroit cop fighting public apathy, a slow court process and "misery." Detroit just logged its highest homicide rate in 20 years.

"The results show that, on average, retired police officers die significantly younger than retired general city employees and they have significantly shorter retirements prior to death than general city employees," said the study published in the authoritative Police Quarterly.

The possible reasons why? "One explanation calls attention to officers' maladaptive responses to the demands of the job. Specifically, the nature and demands of the job--shift work, exposure to misery and conflict, constant potential for danger, risk of physical injury, public apathy, and court process--may lead officers to certain dysfunctional habits and attitudes as coping mechanisms. These habits and attitudes may result in unhealthy outcomes."

Other reasons: "Alcohol-related liver disease as a cause of death was found to be twice that of the general population, lung cancer deaths are also more common among the police." And some just miss the job. "Retirement involves leaving not only the job but everything that it represents. As it has been described many times, being a police officer is not just a job; it is a way of life. Retirement then means losing more than just an association with a job; it involves leaving a strong subculture that has been in place since the start of the officers' career."

The study looked at 7,325 Detroit city employees who retired between 1995 and 2010. Some 452 were cops.

They found that police normally retired earlier because they joined city service earlier. Typically, a Detroit officer retired at age 53 compared to 60 for city workers.

But, on average, they also died six years younger than other city workers. In parallel, police had retirements lasting about six years less than other city workers.