Life looks a little rosier after 50, a new study finds. Older people in their mid-to late-50s are generally happier, and experience less stress and worry than young adults in their 20s, the researchers say.

The results, based on a Gallup phone survey from 2008 of more than 340,000 Americans, held even after the researchers accounted for factors that could have contributed to differences in well-being with age, such as whether the participants were married, had children at home or were employed.

So if having a partner and getting rid of the kids aren't responsible for the uptick in happiness and general life satisfaction with age, then what is? More studies will be needed to find out, the researchers say.

Two ways to look at life

The findings agree with previous work showing well-being varies with age. And some studies have narrowed things down to suggest that happiness comes with being old, male and Republican.

However, the current work included measures of both overall happiness (called global well-being) and day-to-day experiences of specific feelings such as stress and happiness (called hedonic well-being).

These two measures of well-being are rarely included in the same study, Stone said. But they are both important, since global well-being provides a more reflective look at life while hedonic well-being gives a more immediate view, he said.

The immediate, hedonic measures — happiness, enjoyment, stress, worry, anger and sadness — all changed with age, but they showed very different patterns. For example, stress and anger steadily decreased from young adulthood through old age. But worry was fairly constant until age 50, when it declined. Sadness levels rose slightly in the early 40s and declined in the mid 50s, but overall sadness didn't change much with age.

And people's overall satisfaction with their lives showed a U-shaped pattern, dipping down until about the age of 50 before trending upward again.

Men and women showed very similar patterns in terms of how well-being changed with age, though women tended to have higher levels of stress, worry and sadness. However, women had about the same levels of happiness as men and tended to feel better overall about their lives, especially during the first 50 years.

The results emphasize the importance of looking at hedonic well-being since these feelings, particularly the negative ones, don't all vary the same way as we age, Stone said.

"Looking at well-being really needs to be multidimensional and more comprehensive than might be suggested by the current literature," he said.

Why are older people happier?

There are several theories that might explain why people feel better with age that don't have to do with lifestyle factors. It could be, for example, that older people are better at controlling their emotions than younger people. Or it might have something to do with nostalgia, the idea that older people remember fewer negative memories and so are happier.

Also, older people might focus less on what they have or have not achieved, and more on how to get the most out of the rest of their lives, Stone said.

The results will be published this week in the journal Proceedings of the National Academy of Sciences.