Not since the Selective Service Board sent “greetings” to 18-year-old men during the Vietnam War has a birthday salutation been so dreaded by so many. True, the leading edge of the baby boom wont get the official invitations into the quagmire of the 50s for four more years-but these things are always worse in anticipation than in reality. And the icons of the baby boom are already there. Paul McCartney turned 50 this year; so did Aretha Franklin. Bob Dylan is 51, as are Frank Zappa, Paul Simon and Art Garfunkel. Even the heartthrobs have crossed the great divide: Raquel Welch is pinned up at 51, Robert Redford at 55.

Month by month, individually and collectively, the generation that refused to grow up is growing middle aged. The reminders are everywhere-from the gracefully aging Lauren Hutton (49) in the J. Crew catalog to the now ubiquitous prefix “aging baby boomers” to the Oval Office itself. Sure, Bill Clinton and Al Gore will breathe new youth into the presidency that has been held for three decades by the PT-109 crowd. But for many in this competitive cohort, their ascension is just one more reminder of time marching on and leaving accomplishment victims in its wake. See-the president is 46. You’re 49. Weren’t you supposed to be CEO by now, or at least know what you want to DO with your life?

To be sure, this is hardly the first generation to hit or anticipate the Big Five-Oh. The baby boomers’ group obsession with aging is already sounding, well, old, to everybody else, and, by conventional definitions at least, most boomers have been “middle aged” since they turned 40. But raised with such outsize expectations of life, they may have a tougher time accepting the age of limitations than other generations. “This group was somehow programmed to never get older-that sets us up for a whole series of disappointments,” says psychiatrist Harold Bloomfield in Del Mar, Calif. Rice University sociologist Chad Gordon has another take on the angst that is seizing baby boomers. “Let’s face it-aging sucks,” he says. “It’s filled with all those D words-decay, decrepitude, degeneration, dying … Then there’s balding, paunchiness, losing sex drives and capabilities, back trouble, headaches, cholesterol and high blood pressure-they all go from the far horizon to close up. Then you worry about worrying about those things.”

In truth, authorities on aging and ordinary people who’ve been there say that middle age isn’t so bad. “It’s the most powerful and glorious segment of a person’s life,” says Ken Dychtwald, whose company, Age Wave, counsels businesses on how to serve the needs of the aging population. Dychtwald admits, however, that American culture hasn’t universally embraced this idea and that most of the soon-to-be-middle-aged themselves haven’t gotten into the swing of it yet.

Instead, they are responding with ever more exaggerated forms of foreboding. Bloomfield says he sees an increase in a once rare condition called dysmorphophobia-the intense but unfounded fear of looking ugly. In Hollywood, not only do actresses try desperately to disguise their age, but so do agents, scriptwriters and studio executives. “It’s hard to age gracefully out here,” says Dr. Mel Bircoll, 52, considered the father of the cosmetic pectoral implant, the calf implant and the fat implant (which he layers into face-lifts to add contour and avoid the “overstretched look”). Bircoll says his clients used to start at 55. Now they come to him at about 45.

All of this might have been grist for a great TV series, but when producer Stan Rogow tried it this season, it flopped. Rogow intended “Middle Ages” to be an upbeat portrayal-“pretty hip, pretty life affirming, not angst-ridden. What we tried to do with the show was to say, ‘This is OK. It’s better than OK’.” Critics liked it but viewers never gave it a chance and, in retrospect, Rogow understands why: “The name was a colossal mistake. ‘Middle age’ is this horrible-sounding thing you’ve heard throughout your life and hated.” As the low ratings piled up, Rogow said to himself: “We have a problem here, and it’s called denial.”

But the funny thing about denial is that sometimes it works. In the very act of staving off physical aging through exercise, diet and dye, the StairMaster set has actually succeeded in pushing back the boundaries of “middle age.” Boomers will look, act and feel younger at 50 than previous generations did. “Fifty will be like 40,” says UCLA gerontologist Fernando Torres-Gil, who predicts that this generation won’t confront “old age” until well into their 70s. The broad concept of middle age is starting later and lasting longer-and looking better than ever before. “We’re seeing that 50 means all kinds of very vibrant, alive, sexy, dynamic people,” says June Reinisch, director of the Kinsey Institute for Research in Sex, Gender and Reproduction at Indiana University. “I’m 49 this year. I wear clothes that my mother never would have thought of wearing when she was this age. When skirts went up, my skirts went up.” Rogow, 44, says: “I’d really be shocked if I’m wearing plaid golf pants at 60. I suspect I’ll be wearing the same ripped jeans I’ve been wearing for 20 years. They’ll be much cooler then.”

The new middle age also features more children than ever before, since this generation has delayed marriage and childbearing. Many men are having second families, with even younger children, well into their 50s. Some may be pushing strollers and paying college tuition just when psychologists say they should be busting loose and fulfilling themselves. At the same time, today’s middle-agers have aging parents who are starting to need care. “For many people, 50 will be just like 20, 30 and 40-tied to providing basic subsistence needs,” says University of Texas psychologist David Drum. “They won’t see a chance to change, to repattern their lives.”

Yet even as they postponed family responsibilities, many people in this fast-track generation reached the peaks of their careers much earlier than their parents did-and are wondering, “Is that all there is?” even in their 30s and 40s. Many of them will top out earlier, too, as record numbers of middle managers chase fewer and fewer promotions. While previous generations worried about sex and marriage, “career crashes are the baby boom’s version of midlife crisis,” says Barry Glassner, a University of Southern California sociologist. Women, having forged careers of their own in record numbers, may face the same kind of professional crisis traditionally reserved for men-and their incomes will still be needed to make ends meet. “Lose a job-have any piece of the puzzle taken out-and the whole thing falls apart,” says Andrea Saveri, a research fellow at the Institute for the Future in Menlo Park, Calif.

The cruel demographic joke is that just as this generation is hitting middle age with unprecedented family responsibilities, corporate America is mustering legions of fiftysomethings out of the work force through early-retirement plans and less compassionate methods. “There is tremendous doubt about the future,” says Saveri. “People see their friends getting pink slips. Their M.B.A.s aren’t doing them any good now.” Retiring earlier-and living longer-will bring a host of financial, emotional and psychological problems in the years ahead. Today’s 50-year-olds still have 20 or 30 more years to live. What are they going to do-and how are they going to pay for it? “The 50s are not the beginning of the end-you have an awful long way to go,” says University of Chicago gerontologist Bernice Neugarten, now 76. And that may be the most frightening thought of all.

Midway life’s journey I was made aware That I had strayed into a dark forest, And the right path appeared not anywhere.

Dante was 35 years old and frustrated in his quest for political position in 1300 when he wrote the first lines of “The Inferno”-describing perhaps the first midlife crisis in Western literature. Shakespeare charted similar midlife muddles in “King Lear … Macbeth,” “Hamlet” and “Othello” in the early 1600s, though he barely used the phrase “middle age.” Sigmund Freud and Carl Jung studied midlife transitions around the turn of the 20th century. But then “midlife” came much earlier in time. In 1900, average life expectancy in the United States was 47 and only 3 percent of the population lived past 65. Today average life expectancy is 75-and 12 percent of the U.S. population is older than 65.

The longer life gets, the harder it is to plot midpoint and define when middle age begins and ends. “We’ve broken the evolutionary code,” says Gail Sheehy, author of “Passages” and “The Silent Passage.” “In only a century, we’ve added 30 years to the life cycle.” Statistically, the middle of life is now about 37, but what we think of as middle age comes later-anywhere from 40 to 70. As chronological age has less and less meaning, experts are groping for other definitions. When the American Board of Family Practice asked a random sampling of 1,200 Americans when middle age begins, 41 percent said it was when you worry about having enough money for health-care concerns, 42 percent said it was when your last child moves out and 46 percent said it was when you don’t recognize the names of music groups on the radio anymore.

However it is defined, middle age remains one of the least studied phases in life. “It’s the last uncharted territory in human development,” said MacArthur Foundation president Adele Simmons in 1989, announcing a $10 million grant to fund the largest scholarly look ever at the period. Team leader Gilbert Brim and his colleagues at the Research Network on Successful Midlife Development are now partway through their eight-year effort, trying to answer, among other things, why some people hit their strides at midlife and others hit the wall. To date, they have concluded that there are no set stages or transition points-that what happens to people is more the result of accident, personal experiences and the historical period in which they live. “Midlife is full of changes, of twists and turns; the path is not fixed,” says Brim. “People move in and out of states of success.”

In particular, Brim’s group debunks the notion of a “midlife crisis.” “It’s such a mushy concept-not like a clinical diagnosis in the medical field,” he says. But, Brim adds, “what a wonderful idea! You could load everything on that-letting people blame something external for what they’re feeling.” Other scholars agree that very few people suffer full-blown crackups-and that dumping the spouse for a bimbo is more the stuff of fiction-or fantasy-than reality. So is the Gauguin syndrome: running off to Tahiti at 43. People do have affairs and end up with different mates-but that is often after marriages have failed for reasons other than midlife malaise.

Still, the mythology persists. “You ask people if they’ve had a midlife crisis and some say they have,” says sociologist Ronald Kessler at the University of Michigan’s Institute for Social Research. “Then you ask them what it was and they’ll say that they didn’t get to be vice president. So what did the do-try to be vice president. So what did they do-try to kill themselves? Buy a sports car? Well no, people come to terms with getting older in a most gradual way.” The idea of a crisis sometimes provides an excuse for wild and outrageous behavior, says psychologist Susan Krauss Whitbourne at the University of Massachusetts at Amherst: “It sounds romantic and fun-certainly better than complete boredom.” She also suspects it’s a class phenomenon: well-educated people with money “have the luxury to reflect on these things.”

What does commonly happen, experts say, is a more subtle acceptance of life’s limitations. One key task may be to change your self-image. “A lot of the more tangible rewards come in the first half of life, such as good grades, first jobs, early promotions, marriage, first children,” says psychologist Robert E. Simmons in Alexandria, Va. After that, “it’s harder and harder to rely on external gratifications because there aren’t as many. So one is thrown back more on one’s internal self-esteem system.” That can mean finding new forms of satisfaction-from coaching Little League to taking up the saxophone to tutoring kids in school.

The sooner you accept the idea that life may not turn out as you planned, the easier the transition will be. “It’s the person who has just been driving himself and getting burnt out, who is starting to turn 50 and who feels like, ‘My God, my life is over’,” says Bloomfield. Gail Sheehy agrees: “For those who deny, postpone, elude or fantasize to escape coming to terms with [reality], it comes up again around 50 with a double whammy.” Sheehy can see this now, at 54. She barely mentioned life past 50 in “Passages” because she was only 35 at the time and couldn’t visualize herself at an older age. Now she says she knows that “you have to work your way up to saying ‘I’m not going to go backward. I’m not going to try to stay in the same place. That way lies self-torture and eventually foolishness. I’m going to have the courage to go forward’.”

Contrary to conventional wisdom, many people find that the 50s is actually a period of reduced stress and anxiety. “In terms of mental health, midlife is the best time,” says Ronald Kessler. One tantalizing bit of biomedical research has found that between 40 and 60, people actually lose cells in the locus coeruleus, the part of the brain that registers anxiety, which may help explain the “mellowing” many people feel in middle age. Depression does tend to peak in this period, however, which may also be linked to biochemical changes in the aging brain.

Not all mood shifts are biochemical. There are definite life events that can bring about profound changes of heart and direction. The list includes divorce; illness; losing a job; the kids leaving home (or returning); the death of parents, spouses and friends. Those can happen at any point in life, but they begin to mount up in the 50s. Any kind of change is stressful and simply fearing these things can bring tension. “It also happens when mentors retire,” says University of North Carolina sociologist Glen Elder. “You have to think about yourself playing that role. It’s a major transition, one that is hard to come to terms with.”

Professional disappointments weigh especially heavily on men, and they are inevitable even for the most successful, from George Bush to laid-off steelworkers. Being forced out of a job in midlife can be devastating-or liberating, if it brings about a rethinking of what’s most important. Men (and increasingly, women) who sacrificed time with their families for their careers in their younger years may be particularly regretful when success proves as empty as the nest. “Men our age have lived such a macho fake life,” says Rogers Brackmann, 61, a former advertising executive in Chicago. “When I was in the agency business, I was up at 5 o’clock, home at 7:30. For the first 15 years I worked every Saturday. I didn’t make it to my kid’s Little League games. When I left that environment I realized how hard and unproductive the work was.” Rogers packed it in five years ago and says, “I was so happy to get out I can’t describe it.” Since then he has turned to other new businesses, including inventing, and now holds five patents-including one for a golf-ball washer that doesn’t get your hands wet.

Can I ask you a question? Why do men chase women? … I think it’s because they fear death.

–ROSE (Olympia Dukakis) in “Moonstruck”

Ideally, that crossing should be liberating for both halves of the couple and bring them closer together. But often the transition is rocky. “It can be very threatening for men to see their women soar,” says counselor Sirah Vettese, Bloomfield’s wife. Some men are so unnerved that they do seek out younger, more compliant women, Gutmann says. He thinks Ernest Hemingway is a prime example: devastated after his third wife left him to pursue her own career, the author became increasingly alcoholic. He took another younger wife and killed himself at 61.

It doesn’t help that many men wrestling with self-image adjustments in midlife must also accept declining sexual performance. Testosterone levels gradually drop, which can diminish their libido. Erections are less full, less frequent and require more stimulation to achieve. Researchers once attributed that to psychological factors, but increasingly they find that 75 percent of erection dysfunctions stem from physiological problems. “Smoking, diabetes, hypertension, elevated cholesterol-without a doubt, those are the four erection busters,” says University of Chicago urologist Laurence A. Levine. Still, psychology does play a role. “If you think you’re going to have a problem, suddenly you’re going to begin having a problem,” says psychologist Jan Sinnott at Towson State University in Baltimore, Md.

Inevitably, pharmaceutical manufacturers have sensed that there’s money to be made in the fear of flaccidity. Gynex Pharmaceuticals is researching a daily under-the-tongue testosterone-replacement product called Androtest-SL and already markets an injectable version that is used every two weeks. But there may be considerable side effects. Excessive use of testosterone may lead to testicular atrophy and infertility and spur the growth of some cancers. Too much testosterone can cause some men to grow small breasts, too.

A better remedy for men who find their potency declining is to change the way they thin about sex-to take things slower, more romantically and not mourn the seemingly instant erections of their youth. “The midlife male has to finally get the idea that his primary sex organ is not his penis. It’s his heart and his brain,” says Bloomfield, author of “Love Secrets for a Lasting Relationship.” Talking helps, too, though most men are not accustomed to such openness. “It’s really important that men and women sit down and say to each other, ‘Our lives are changing’,” says Vettese.

In many ways, women have it easier in midlife. For all the new willingness to discuss the hot flashes and mood swings some feel during menopause, many women feel a surge of sexual and psychological freedom once their shifting hormones rebalance and they are no longer concerned about getting pregnant. “With each passing generation, women feel sexier and more desire after menopause,” says June Reinisch at the Kinsey Institute. Sheehy says that based on studies she has seen, about one third of women have some noticeable diminution of desire after menopause. That can be rectified with hormone supplements or accepted as it is, if the woman doesn’t mind.

What many women do mind is finding themselves alone and lost in the discouraging midlife singles scene. Zella Case, co-owner of the Someone Special dating service in Dallas, says, “We have hundreds of women who want in, but so few men.” The numbers are right there in the census statistics: there are 14 million single women older than 55, and only 4 million single men. Just ask Victoria Anderson, a Dallas private investigator who turned 50 last month. Divorced 13 years, she’s been losing confidence and gaining weight and she frets that she’ll never fit into the size 3s in her closet again. She despairs meeting a new mate on the job-“I deal with criminals and jerks,” she says. And as far as the bar scene goes, Anderson says ruefully, the typical question now is not “what’s your sign, but what’s your cholesterol level?”

Women with stable marriages may find other tensions mounting in midlife. With delayed childbirth, kids may be hitting adolescence just when their mothers are in menopause-a volatile combination. Some women desperately fear losing their faces and their figures-especially if those have been the focus of their self-esteem. But the new burst of postmenopausal independence some feel may help to compensate.

Bobbi Altman literally took flight at midlife. “Turning 50 was the best thing that ever happened to me. I could do anything I wanted to,” she says. After suffering through a divorce in her early 40s and raising three children, Altman took up aviation, bought an airplane and, at 59, went to aircraft-mechanic school. Last April she graduated and in June she flew cross-country solo. Now 61, she lives in Laguna Beach, Calif., and is involved with a man who finished law school at 70. Altman flies to work every day at the Santa Monica Museum of Flying, where she is helping to restore a World War II P-39. “Aging is not a loss of youth-it’s another stage,” she says.

I remember now that the toughest birthday I ever faced was my fortieth. It was a big symbol because it said goodbye, goodbye, goodbye to youth. But I think that when one has passed through that age it’s breaking the sound barrier.

–Writer and director NORMAN CORWIN, 82 quoted in the 1992 book “The Ageless Spirit”

Still, the image of elderly people as desperate, frail and unproductive prevails, and that brings an unrealistic fear of growing middle aged and older. “People need to profoundly rethink what aging means, not only for themselves as individuals, but for the whole society,” says Harry Moody, deputy director of the Brookdale Center on Aging at Hunter College in New York. By 2030, when the oldest boomers are 84 and the youngest have turned 65, there will be an estimated 65 million Americans 65 and older-more than twice as many as today.

To find more satisfaction and hope in that future, aging baby boomers need to bust out of the rigid “three boxes of life” mentality that has governed the pattern of American lives for so long. Confining education to youth, work and child rearing to the middle years, and retirement to old age makes less and less sense-and it simply won’t fly in an economy that is dismissing people from work world in their 50s, with an ever-longer stretch of life ahead. “We desperately need some real, contributing roles for people in the third third of life,” says New York management consultant Bill Stanley. He argues that the whole concept of “retirement” should be retired.

Some change in the image of aging will come about naturally in the decades ahead. Baby boomers, by sheer force of numbers, have always made their stage in life the hip stage to be in. The generation that thought it could change the world overnight has only a few years left before its members become elders themselves. While some of their frantic efforts to stave off aging may constitute denial, some go hand in hand with forging a healthier, more constructive vision of old age that could last even longer than we now suspect. The boomers will go there, riding StairMasters to heaven, and that may be their most lasting legacy of all.

..MR5-

Percentage of baby boomers who say they have been through midlife crisis: 27

Average age of men who marry for second time: 39.2

Average age of women who marry for second time: 54.8

SOURCE: GALLUP, NATIONAL CENTER FOR HEALTH STATISTICS

Percentage of men aged 40 to 49 who say their lives are exciting: 52.4

Percentage aged 50 to 59: 43.3

Percentage of women aged 40 to 49 who find their lives exciting: 45.6

Percentage aged 50 to 59: 40.7

SOURCE: NATIONAL OPINION RESEARCH CENTER

Percentage of married men aged 40 to 49 who admit to infidelity: 28.4

Percentage aged 50 to 59: 24.3

Percentage of married women aged 40 to 49 who admit to infidelity: 15.21 Percentage aged 50 to 59: 3.3

SOURCE: NATIONAL OPINION RESEARCH CENTER

Total face-lifts in U.S., 1990: 48,743 (91% women) percentage aged 35 to 50: 27 percentage aged 51 to 64: 58

Total tummy tucks in U.S., 1990: 20,213 (93% women) percentage aged 35 to 50: 64 percentage aged 51 to 64: 15

Total hair transplants in U.S., 1990: 3,188 (100% men) percentage aged 55 to 50: 57 percentage aged 51 to 64: 10

Median age of an American using hair-color product: women: 43.14, men: 45.02

SOURCE: AMERICAN SOCIETY OF PLASTIC & RECONSTRUCTIVE SURGEONS, SIMMONS 1992

How do I know if what I achieve in life should called serenity and not surrender?

–JUDITH VIORST, 61

Twenty-five years ago I worried about getting the clap. Now I worry about getting the clapper.

–HUMORIST ROSS K. BAKER, 54

I feel exactly the same as I’ve always felt: a lightly reined-in voracious beast.

–JACK NICHOLSON, 55

I live like a monk, almost. A monk with red lips, short dresses and bis hair.

–TINA TURNER, 53