MONDAY, Oct. 31 (HealthDay News) -- A new British study finds that older adults who report feeling happy and content live longer than others.

But the research doesn't prove that happiness leads to longer life, and the study authors also found that high levels of negative emotions such as anxiety didn't take years off people's lives.

Still, "the study therefore points to a fascinating link between how happy we feel on a moment-to-moment basis and survival," said study author Andrew Steptoe, director of the Division of Population Health at University College London.

"The challenge now is to establish what the underlying processes are, and whether we can harness these to improve people's health," Steptoe said.

Researchers think that happiness has a connection to health, but the challenge is figuring out the particular mechanisms at work. "Does illness make you feel less happy, or does happiness protect against illness? This research is about the second of these possibilities," Steptoe said.

The study appears online Oct. 31 in the Proceedings of the National Academy of Sciences.

The study authors asked about 3,850 people aged 52 to 79 to describe their feelings -- happy, excited, content, worried, anxious or fearful -- four times during one 24-hour period. The volunteers were participating in a study on aging. The researchers' goal was to monitor what's known as "positive affect" and "negative affect." Positive affect is an umbrella term referring to states such as happiness, peacefulness and excitedness. Negative affect is the opposite -- anxiety, for example.

Next, the researchers tracked the participants to see how many died over the next five years. More than 7 percent of those who were in the lowest third -- those reporting the least happiness -- died. By comparison, only 3.6 percent in the third with the highest level of self-described happiness did.

Even after researchers adjusted their figures so they wouldn't be thrown off by factors such as income, gender, depression and health, those who said they were the most happy were 35 percent less likely to die than those who described themselves as the least happy.

The adjustments for influences such as illness and finances meant that the study's finding "was not because the people with high positive affect were younger, wealthier, more educated or more healthy at baseline," Steptoe said.

The researchers questioned why negative affect was linked to shorter lifespans.

"One reason seems to be that feeling depressed and low was linked with having a pre-existing illness," Steptoe said. "So when we took baseline illness into account, the links between depression and survival were no longer significant."

The study authors acknowledged several limitations of their study. For one thing, it looked at overall deaths, but not specific causes such as cancer. Also, the researchers only assessed well-being in one 24-hour period, and they did not assess individual risk factors such as obesity.

Still, although the study doesn't prove that happiness leads to a longer lifespan, one expert thinks the take-home message is pretty clear. "The overwhelming suggestion is that we should work hard to boost positive emotions in our daily lives," said Sonja Lyubomirsky, a professor of psychology at the University of California, Riverside, and author of the book "The How of Happiness: A Scientific Approach to Getting the Life You Want."

More information

For more about stress and health, see the U.S. National Library of Medicine.