As Congress and the Obama administration grapple with ways to extend affordable health insurance to all Americans, one especially vulnerable group is again in the spotlight. They are uninsured people ages 50 to 64 who are caught in a frightening twilight zone of health care—old enough to be facing more medical problems but too young for Medicare.

The idea of giving special coverage to this age group—perhaps by allowing them an early buy-in to Medicare—has been proposed from time to time over the past 15 years. But now, as the boomers swell the ranks of the middle-aged at a time when many are losing their jobs, their plight has become more visible and urgent.

“The economic turndown has pushed many of them into early retirement, and in doing so they’ve lost their employer-sponsored health coverage,” says John Rother, AARP’s executive vice president for policy and strategy. For those without such coverage, working or not, the only option is often to buy private individual insurance. But in this market, “the practice of excluding people for preexisting conditions has grown and left many people unable to get insurance at any price,” Rother adds. “Constantly increasing health care costs have also priced many others out of the market—in most states, there is really no affordable insurance for older people who don’t have employer coverage.”

More than 55 million boomers are now in their 50s or early 60s, with this number expected to grow to 63 million, or 19 percent of the population, by 2015, according to the U.S. Census Bureau. In this age range, an analysis by AARP’s Public Policy Institute shows that:

• more than 7 million are uninsured.

• at age 50, nearly one in six people applying for individual insurance are rejected, and at age 60 this rises to one in four.

• those who manage to buy individual insurance pay premiums that are, on average, three times higher than premiums paid through employer coverage.

• among those with individual coverage, 67 percent spend at least 10 percent of their after-tax income on health care, compared with 25 percent of those with employer coverage.

Among people sending questions to the “Ask Ms. Medicare” column on the AARP Bulletin Today website, an increasing number are under age 65. They’ve typically just lost employer coverage, usually through layoffs, and are desperately trying to find alternative insurance. “When can I get Medicare?” they often ask. But under current law people younger than 65 can qualify for Medicare only if they receive Social Security disability benefits, or have Lou Gehrig’s disease or kidney failure. And those granted disability payments must wait two years before becoming eligible for Medicare.

Over the years, advocacy groups and some members of Congress have proposed extending Medicare to uninsured people under 65—with eligibility beginning at 50, 55, 60 or 62, depending on the proposal.

A recent effort is the Medicare Early Access bill introduced May 8 by Sen. Jay Rockefeller, D-W.Va., chairman of the Senate Finance Subcommittee on Health Care. This bill would make it possible for those 55 to 64 to buy into Medicare and receive a 75 percent government subsidy, through a federal tax credit, to make the premiums for Part A (hospital insurance) and Part B (outpatient medical services) more affordable. A cosponsor, Sen. Benjamin Cardin, D-Md., said that the legislation, which is supported by AARP, “is an important step forward on our current path toward a universal, affordable, quality health care system that protects employer-based coverage and expands public options.”

This targeted approach will likely be superseded by the push for general health care reform that is currently preoccupying Congress, experts say. “Right now, the conversation is at a more universal level, looking at broad system reforms that would increase coverage for everyone, including this age group,” says Sara Collins, assistant vice president of the Program on the Future of Health Insurance at the Commonwealth Fund research group in New York.

The Senate Finance Committee, for example, released a document earlier this month describing a number of possible policy options for achieving near-universal coverage. One central proposal, likely to be part of any final package, is to create a health insurance exchange through which individuals and small businesses can choose coverage from a menu of insurance options. Subsidies would be given to people who couldn’t afford the premiums.

The discussion paper also proposes a Medicare buy-in for people ages 55 to 64—but only as a stopgap measure until the insurance exchange is up and running. This proposal is far less generous than the Rockefeller bill. Enrollees in the temporary buy-in would pay an estimated $600 to $700 a month in premiums, with none of the subsidies that Medicare beneficiaries currently receive, plus an extra five percent to cover administrative costs. Furthermore, if Medicare’s costs for this age group turned out to be higher than expected, enrollees would be required to make up the difference by paying a surcharge on premiums in the regular Medicare program after they turn 65, “and continue doing so until they turn 85,” the document says.

One important proposal is a federal ban on the practice in the individual insurance market of denying people coverage or charging them much steeper premiums for preexisting health conditions. This in itself would greatly benefit uninsured people 50 to 64 years old, even if no Medicare buy-in materializes. About one in four people in this group are in fair or poor health, compared with about one in 10 of those of the same age who have employer coverage, according to a recent report from the Kaiser Family Foundation. And this is the age when chronic health conditions such as diabetes and heart problems most often begin to show up.

But, under the same proposal, insurers would still be able to charge higher premiums based on age—up to five times as much for this age group as they charge younger people.

Massachusetts, which brought in mandated coverage for all residents in 2007 and uses a health insurance exchange to help the uninsured find affordable coverage, also allows age rating there, although insurers cannot charge older people on average more than double the premium amounts asked of the young. Even so, many older state residents are already feeling sticker shock as they pass another birthday milestone and see their premiums suddenly hiked by as much as 45 percent, consumer advocates say.

If Congress fails to pass system-wide reforms this year, more incremental measures targeting certain groups—such as people ages 50 to 64—could gain more traction. In that situation, Collins says, “a Medicare buy-in would be very positive for this age group.” Opinion polls since 2000 consistently show that around 75 percent of Americans support the idea, the Kaiser report says.

But, as ever, a lot depends on the details. Would the government offer heavy subsidies? That would make a buy-in attractive for consumers but would likely make Congress balk at the overall cost. Without subsidies, only the sickest people might find it worthwhile and their costs over time would inevitably push premiums even higher.

Another concern is whether a Medicare buy-in, if subsidized and affordable, might lure insured people away from employer-based coverage—a scenario almost nobody in Congress wants to see happen.

AARP’s Rother is skeptical. “In most work-based plans, the employer pays about 75 percent of the premium and employees pick up about 25 percent, so in that situation they won’t do better by leaving the plan,” he says. “And even if the buy-in carried a 75 percent subsidy, most employer plans provide much better coverage than Medicare, which on average pays only about half of beneficiaries’ costs.”

Patricia Barry is a senior editor at the AARP Bulletin.