Employers, beware. Your overworked employees may not be around much longer.

Once they sense the job market has improved, they plan to bolt and let the door close on their immediate boss.

This is the message being sent in MetLife's ninth annual Study of Employee Benefits Trends.

At least one third of employees said they hope to be working somewhere else in the next 12 months, according to the survey. And employees who plan to leave are more likely to report greater job insecurity and workload increases.

According to MetLife, 51 percent of those who "strongly agree" they have experienced an increased workload and 42 percent who "strong agree" they have experienced decreased job security said they hope to be working elsewhere this year.

In comparison, just 31 percent who "strongly disagree" they have experienced an increased workload and 13 percent who "strongly disagree" they have experienced decreased job security said they hope to be working elsewhere this year.

The Study also shows many measures of employee engagement such as job satisfaction are starting to decline.

For example, in this year's survey, 51 percent said they are satisfied with their job. This is down from 59 percent two years ago in the depths of the recession.

During that period, the percentage that said they have a strong sense of loyalty to their employer also dropped, to 47 percent from 59 percent.

"These trends are a clear warning of potential problems in the near future," MetLife states in its report. "Employers have kept talented employees through the recession. Are they about to lose them just as things start to turn around?"

The report then emphasizes that value of benefits in helping the business goals of employee attraction, retention and productivity. It found that employees who report that they are very satisfied with the benefits they receive through work are more than three times as likely to indicate that they are highly satisfied with their current job compared with those who are very dissatisfied with the benefits program.

The study also found a link between employee benefits satisfaction and retention. Those who indicate that they are highly satisfied with their benefits are less likely to say that they are hoping to leave in the next 12 months and more likely to confirm that benefits are an important reason why they remain with their current employer.