More than half of the first wave of baby boomers are fully retired, according to a new study by MetLife Mature Market Institute.

Fifty-two percent of those born in 1946 are fully retired, says the study, "Healthy, Retiring Rapidly and Collecting Social Security: The MetLife Report on the Oldest Boomers." Six years ago, when MetLife began following those born in 1946, 19 percent were retired; two years ago that number had jumped to 45 percent.

Twenty-one percent of 67-years-olds are still working full time, while 14 percent are working part time. The rest are seasonally employed, on disability or self-employed.

Of those who are fully retired, 38 percent said they were ready to retire (they wanted to be through with work), 17 percent said they retired for health reasons and 10 percent said they lost their jobs. The rest retired for other reasons -- simply because they could afford to or because they wanted to join a retired spouse.

The first wave of boomers are eligible for full retirement benefits from Social Security at age 66 and 86 percent of those born in 1946 are collecting, although 43 percent say they began collecting earlier than planned.

As with all older age groups, long-term care has become a concern and 31 percent of the respondents were concerned about providing long-term care for themselves or their spouse. At the same time, less than 25 percent have long-term care insurance.

Eighty-two percent of the first boomers want to continue living where they are and not move again.

More than 40 percent of the oldest boomers are optimistic about the future and nearly one-quarter are optimistic about their health, but only 20 percent feel good about their personal finances, says MetLife.

At the same time, of those who are retired, only 20 percent feel their standard of living has been lowered since they retired.