BROUGHT ON by the earthquake of world war, this tsunami has been 70 years in the making.

By 2029, one-fifth of the U.S. population will be 65 or older, and many of those 76 million or so postwar baby boomers - perhaps up to 50 million of them - will be exiting the workforce over the same period.

They'll consume more medical care, even as their collective retirement will remove hundreds of thousands of doctors and nurses from the field. They'll need retirement planning services, particularly as they are likely to live into their 80s. They'll be downsizing their homes.

In short, the coming "silver tsunami" will be a potentially seismic force upon the regional, U.S. and world economies - most developed countries are actually far grayer than America - in ways good, and bad.

How bad? Depends on who you ask. There's no doubt that the baby boom was historically big by U.S. and world standards, but some analyses suggest the impact of the retirements won't be as dramatic as has often been predicted. Given that Americans continue to work well past 65 and that tens of millions of boomers never entered the workforce, it's possible that the annual U.S. retirement rate will stay relatively constant or tick up modestly over the next two decades.

But even if they keep working, boomers have other challenges ahead of them. Richard Schulz is a professor of psychiatry at the University of Pittsburgh. He's also the associate director of Pitt's Institute on Aging.

In November, Schulz and the social and urban research center published "The State of Aging in Allegheny County," a detailed study of that region's seniors and near-seniors. He discussed those findings last week.

Q: The leading edge of the baby boom, the ones born between 1946 and 1955, are already retiring, or thinking about it. Are they prepared for retirement?

A: People feel more insecure about their future financial status, including how they might do in retirement. One consequence of that is people are delaying retirement.

Q: Presumably, business opportunities arise as boomers retire and as our country gets grayer.

A: If you look at the proliferation of retirement facilities in the region, I think that speaks to an opportunity people have picked up on. There are many more high-profile, high-end types of facilities that didn't exist 10 to 15 years ago.

Q: Your aging report noted that the "dependency ratio" in Allegheny County, and elsewhere, is declining fast. In 2010, the number of people available to care for seniors who might need it was 6-to-1. In 35 years, it will be 3.6-to-1.

A: The issue of who provides informal care to the elderly presents a problem. By that, we mean typically family care, often an adult daughter caring for a parent . . . baby boomers have relatively few children available to provide that informal care. It raises the question, "Who is going to fill that gap?"

Q: And who will fill it?

A: One answer might be immigrants . . . in big population centers, it's often immigrants that pay that role. In New York, something like 40 percent of all long-term-care workers are immigrants. This issue may spill over into the immigration debate.

Q: And what happens when the boomers, many of whom may have a parent or two alive in their 80s or 90s, themselves need help?

A: So you have them moving into their own retirement years, with the high likelihood that they still have a parent who's alive, who's highly disabled, who needs care. They are entering their own life phase where they have health and disability problems, but at the same time are pressed to provide care for a parent. . . . It's a pretty overwhelming problem.

Q: Why can't doctors and professional caregivers fill that void?

A: We have very few health-care providers - primary care physicians, nurses - who are trained in geriatric care. That will become worse as the proportion of the older population increases.

Q: It's a pretty depressing picture for baby boomers.

A: One of the nice things about aging is that, if you look at depression levels, older persons are doing much better than the baby boomers. That's a typical age-related phenomenon. Older people are good at learning to regulate their lives in ways to maximize positive life experiences and do things that are enjoyable, rather than doing things you have to do.