A happy heart just might be a healthier one as well. British researchers from University College, London studied 2,873 healthy men and women between the ages of 50 and 74 years between 2002 and 2004. Over the course of one day, participants collected six samples of their saliva so that the researchers could measure their cortisol levels (a stress hormone that, when chronically elevated, may contribute to high blood pressure, abdominal obesity and dampened immune function, among other problems). After taking each sample, participants recorded their current mood - the extent to which they felt happy, excited or content. The researchers also measured the participant's levels of C-reactive protein and interleukin 6, two markers of inflammation in the body. They found that men and women who reported happier moods had lower cortisol levels over the course of the day - even when factors such as age, weight, smoking and income were taken into account. Among women, but not men, positive emotions were also related to lower levels of C-reactive protein and interleukin 6. The reason for the sex difference is not clear. Those who reported upbeat moods had lower levels of cortisol. Women who reported more positive emotions had lower blood levels of two proteins that indicate widespread inflammation in the body. Chronic inflammation is believed to contribute to a range of ills over time, including heart disease and cancer. It has been long noted that happier people tend to be in better health than those who are persistently stressed, hostile or pessimistic. But the reasons are still being studied. One possibility is that happier people lead more healthful lifestyles, but not all studies have found this to be the case. The current findings add to the evidence that happiness and other positive emotions are associated with biological responses that are health-protective. The findings suggest another biological process linking happiness with reduced biological vulnerability.
American Journal of Epidemiology,
January 2008