Using long-term data from two nationally representative sample surveys of the U.S. population, the researchers assessed the impact of chronic job insecurity apart from actual job loss.
"Dramatic changes in the U.S. labor market have weakened bonds between employers and employees and fueled perceptions of job insecurity," said University of Michigan sociologist Sarah Burgard.
"This study provides the strongest evidence to date that persistent job insecurity has a negative impact on worker health. In fact, chronic job insecurity was a stronger predictor of poor health than either smoking or hypertension in one of the groups we studied," she added.
The researchers analysed data on more than 1,700 adults, collected over periods from three to 10 years.
They interviewed the same people at different points in time to disentangle the connection between poor health and job insecurity, and to control for the impact of actual job loss and other factors.
One of the studies was conducted between 1986 and 1989, the other between 1995 and 2005.
"It may seem surprising that chronically high job-insecurity is more strongly linked with health declines than actual job loss or unemployment. But there are a number of reasons why this is the case. Ongoing ambiguity about the future, inability to take action unless the feared event actually happens, and the lack of institutionalised supports associated with perceived insecurity are among them," said Burgard.
To measure feelings of job insecurity, participants in one study were asked: "How likely is that during the next couple of years you will involuntarily lose your main job?"
Participants in the other study were asked: "If you wanted to stay in your present job, what are the chances you could keep it for the next two years."
It was found that at any given time, as many as 18 percent of those surveyed felt insecure about their jobs.
However, only about 5 percent of respondents in the first survey and 3 percent of respondents in the second survey reported feeling anxious about their jobs both times they were interviewed.
According to Burgard, the findings have potential implications for both policy and intervention.
"Programs designed for displaced or unemployed workers are unlikely to solve the problems faced by workers who are still employed but are persistently insecure about their jobs. When you consider that not only income but so many of the important benefits that give Americans some piece of mind-including health insurance and retirement benefits-are tied to employment for most people, it's understandable that persistent job insecurity is so stressful," she said.
"We need to learn more about the conditions that generate or change worker perceptions of their job insecurity. Then organizations might want to intervene to reduce perceptions of insecurity or perhaps broader governmental policies might help to mitigate the degree of stress associated with perceived job insecurity. Additional acute and chronic strains at work and in other areas of life might also worsen or mitigate the health impact of long-term job insecurity.
"Certainly job insecurity is nothing new, but the numbers experiencing persistent job insecurity could be considerably higher during this global recession, so these findings could apply much more broadly today than they did even a few years ago," she added.
The study appears in the September issue of the peer-reviewed journal Social Science and Medicine.