Retirement always looms over a person's working life. Many look forward to years of ease, but many dread not having the steady source of income and structured environment working provides. According to the University of Michigan Health and Retirement Study (HRS), most Americans find that retirement is a happy time of life with boosts in personal satisfaction and an improvement in health.

Begun in 1992, the study followed 20,000 Americans over the age of 50, interviewing them every two years until their deaths. Supported by the National Institute on Aging and the Social Security Administration, it collects information on subjects such as income, work, assets, pension plans, physical health, and health care.

A report published this month based on an examination of retirees, found that the improvements in satisfaction don't fade with time. "Retirement has long lasting benefits to individual well-being," the report concluded.

"It seems like retirement is a good place to be," co-author Devon Gorry, an assistant professor of economics at Utah State University, told TODAY.

"People immediately report being happier on average and less depressed," she said.

For the latest report, researchers eliminated people who were disabled, unemployed or forced into retirement because of health issues. They studied people who had worked for a minimum of 20 years and retired when they became eligible for Social Security benefits or a pension plan.

The retirees reported an immediate improvement in health and in their satisfaction with their lives. Four years later, they reported "significant improvements" in health.

Why the delay? The researchers speculate that retirees may adopt healthier habits which take a while to become obvious.

"We find strong evidence that retirement improves both health and life satisfaction," the authors wrote.

"While the impact on life satisfaction occurs within the first four years of retirement, many of the improvements in health show up four or more years later, consistent with the view that health is a stock that evolves slowly," they wrote, adding that the improvements don't come from visiting the doctor more often.