If you want to be happy, focus on health, relationships, simple pleasures and achieving a sense of control of your well-being, according to a survey of more than 4,000 adults age 35+ released today by the AARP. The study looks at how happiness changes over time and how age impacts the factors that are most important to well-being.

The survey confirmed two decades of research suggesting that happiness is U-shaped over the life cycle: It peaks in one's 20s and begins to decline, bottoming out in the mid-to-late 40s and rising again in old age. A study by David Blanchflower and Andrew Oswald, leading researchers in the field of subjective well-being, found that after controlling for factors such as income, education and marital status, "happiness bottoms at age 49 for American males and 45 for American females, and ages 44 and 43 respectively for male and female Europeans." (The AARP study found people hit bottom between age 51 and 55.)

This finding is likely to elicit a chorus of "well, duh!" from people in their 40s and 50s with stressful jobs, mortgages to pay and a couple of kids to get through college. But Oswald and Branchflower also suggest that happiness may bottom in midlife because people come to terms with failed dreams; in his 40s or early 50s, the unsuccessful Hollywood actor finally acknowledges that his day job is his real job:

"...individuals learn to adapt to their strengths and weaknesses, and in mid-life quell the infeasible aspirations of their youth," write Oswald and Branchflower.

Meanwhile, among older people "a kind of comparison process is at work: I have seen school-friends die and come eventually to value my blessings during my remaining years," Oswald and Branchflower write. They also have more time to spend on two factors that are key to happiness: friendships and simple pleasures.

So who is happy? The AARP study found women tend to be slightly happier than men; people who are married or in a relationship are happier than singles and never-marrieds; and people who are retired or currently employed are significantly happier than people not employed for pay. Education also helps: Just 23 percent of people with a post-graduate degree rated themselves "not too happy" compared to 37 percent of those with only a high school degree.

Check out the slideshow below for eight factors that contribute most to happiness, according to the AARP study.

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  • Health

    Health was "extremely important" to happiness for 73 percent of respondents. People in "good or excellent" health are three times more likely to report being "very" happy. Interestingly, what may matter most is how healthy you <em>think</em> you are: The AARP found that the percentage of people reporting good health is relatively stable over the 35-80 age range, varying only seven percentage points. That's despite the fact that objectively, older people are in fact not as healthy: The number of people who report they are suffering two or more medical conditions increased 400 percent over the 35-80 age range. (People may be comparing their health to their peers who are in worse shape.)

  • Relationships

    Some 68 percent of respondents called relationships "extremely important" to happiness. Some 72 percent of people who were married or in a relationship called themselves "very happy" or "pretty happy" -- compared to 60 percent of singles. AARP asked respondents to rank the importance of certain activities to happiness, and many of those scoring at the top were relationship-related: 72 percent said "kissing or hugging someone you love"; 72 percent said "watching your children, grandchildren or close relative succeed in what they want to do"; 69 percent said "spending time with your family and friends such as a meal or social gathering'; and 64 percent said "experiencing a special moment with a child." However, relationships did have to be real: "connecting with friends or family on a social media site like Facebook" came in 37th out of 38 activities in contributing to happiness.

  • Pleasure

    Nearly half (47 percent) of respondents said pleasure was "extremely important" to happiness. Among the simple pleasures that were most important to the happiness of people 50 to 80: enjoying natural beauty like a sunset or ocean (64 percent); having someone do something nice for you unexpectedly (56 percent); practicing religious or spiritual faith (50 percent); making progress on personal goals (47%); and being absorbed in a favorite hobby or interest (42 percent).

  • Accomplishment

    Four in ten of those surveyed called accomplishment "extremely important" to happiness.

  • Meaning And Engagement

    Meaning and engagement were considered "extremely important" to happiness among 38 and 37 percent of respondents, respectively.

  • Money

    Some 31 percent of respondents said money was "extremely important" to happiness. Money was slightly more important to people who earned $25,000 or less. As psychologist and Nobel Laureate Daniel Kahneman has noted, <a href="http://www.moneyandhappiness.com/blog/?p=1053" target="_hplink">beyond a household income of $75,000, experienced well-being no longer increases</a>, although people's judgment of how satisfied they are with their lives does continue to increase. At the same time, severe poverty amplifies life's misfortunes, such as illness or divorce. The AARP study found similar results: Income and happiness were positively correlated; when comparing the percentage of those "Very Happy" by income ranges, the slope increases up to the $75,000 mark, then continued to rise even more dramatically. Asked how they would spend $100 on something to increase happiness, most respondents said they would spend it on their family or going out to dinner. This correlates with findings that show <a href="http://www.sciencedaily.com/releases/2009/02/090207150518.htm" target="_hplink">buying experiences makes people happier than buying things</a>.

  • A Sense Of Control Over Happiness

    People who feel they are in control of their happiness report that they are 2.5 times happier than those who believe happiness is out of their control. A sense of control is linked to higher income, higher education, good health and not experiencing a major life event in the past year. This finding also mirrors decades of research suggesting <a href="http://moneyandhappiness.com/get_happy.htm" target="_hplink">autonomy -- the feeling that your actions are self-chosen and self-endorsed</a> -- is a core psychological need. Studies have found people who lack a sense of control -- prisoners, nursing home residents, people living under totalitarian governments -- suffer lower morale and poor health, according to David Myers, a professor at Hope College in Michigan and author of "The Pursuit of Happiness." Interestingly, a sense of control over one's happiness rises with age -- with 69 percent of people age 75 to 80 feeling they have control over their happiness, versus about half of people age 40 to 54. It may be that with the wisdom of the years, people recognize that happiness is a choice.

  • Pets

    Spending time with a pet can be a substantial way to contribute to one's happiness, the survey found, especially for older women: 81 percent of women age 66 to 80 who own pets said spending time with them contributes "a lot" to personal happiness. It was also important to two-thirds of singles.