You suffer more aches and pains. Your middle is expanding, your hairline receding, and new wrinkles seem to pop up like dandelions. Sooner or later, you're bound to get bad news from the doctor. And you're happier than you've been in years.

Wait -- what?

That's right, studies by organizations including the General Social Survey, the Pew Research Center and the Gallup Poll indicate that people in their 50s, 60s and 70s are in better spirits than younger adults. Generally speaking, happiness is high when one enters one's 20s, slides downhill through the 30s and 40s, and swoops up again after 50, continuing to soar for several decades.

Graphed across an average lifetime, the happiness timeline looks like a U-shaped curve. (Some call it a W, to account for the slight rise in the 30s before it dips down again -- experts suspect this represents parents who are enjoying the brief respite between their kids' Terrible Twos and Even Worse Teens.)

Age is just one factor researchers have associated with happiness. Others include income, health, marital status, religiosity and political affiliation. (These are correlations, by the way, not cause-effect relationships -- for example, if married people are happier on average it could be because marriage makes people happy, or because happy people are more likely to be married.)

But unlike, say, wealth, the link between happiness and older age doesn't really make intuitive sense. Why would we grow more cheerful as we lose health, vitality, looks and friends?

Experts aren't sure, though theories abound, said University of Minnesota psychologist Angus W. MacDonald, who teaches a course on happiness.

One possibility, MacDonald said, is that people typically spend early- to mid-adulthood stressing over their life goals: building a career, getting married, having and raising children. Later, having achieved those goals -- or content to have passed them up -- people can relax into a sense of satisfaction.

Or maybe people build stronger coping mechanisms as they age. They keep their expectations modest. They look on the bright side. They anticipate their own reactions to events and make choices they've learned will improve their moods. "You have solved a bunch of problems, some of them you felt crappy about and others you felt better about, and you begin to learn from that," MacDonald said.

As for declining health, in early old age those bad diagnoses may typically come far enough apart not to lastingly thwart happiness, MacDonald said. Research indicates that the impact of momentous events, however wonderful or terrible, tends to be temporary. You revel in your new lottery riches or despair over your new disability, but eventually slip back to whatever level of happiness you experienced before they came along.

Whatever the explanation, Robert Kane, director of the university's Center on Aging, cautions against letting the image of the happy oldster distract from harsher realities.

"I go to too many gerontology meetings where they try and tell people that old age is fun," he said. "Take it from me, it's not."

People enjoying financial security, robust health and active social lives may be happy, Kane said, but "there are a lot of very unhappy old people" who are poor, sick or isolated. A society that doesn't fully recognize their existence won't feel much urgency about addressing those problems.

Indeed, the research itself may be misleading. Susan Jacoby, author of "Never Say Die: The Myth and Marketing of the New Old Age" is skeptical of researchers' tendency to lump "very happy" and "pretty happy" together as a response category, though the latter may be perfunctory -- easier to tell a stranger than "I'm unhappy." Also, researchers may overlook people in adverse conditions, such as those suffering from dementia, thereby skewing the results toward peers in better circumstances.

The studies generally focus on the "young old" under 85, sometimes entirely omitting the "old old" -- among whom, she said, happiness tends to diminish sharply.

"When people live physically beyond a certain point, not only do occasional bad things happen, but bad things happen routinely," Jacoby said in a phone interview. The chances of developing dementia, for example, rise to 50-50. Optimistic baby boomers ignore this "train wreck coming at us" as they age.

The media exacerbate the problem by illustrating aging with cheerful faces, such as celebrities like Jane Fonda and Harry Belafonte -- people who are wealthy, attractive and fit. Most people, in fact, don't age that well, Jacoby said.

"The idea is we're all going to be Betty White," she said. "Yeah, I'd a lot rather be Betty White at 90 than some other people I know who are 90. But she's the exception, not the rule."

Katy Read • 612-673-4583