LONDON (Reuters) – People who are usually happy and enthusiastic are less likely to develop heart disease than those who tend to be glum, scientists said last week, and boosting positive emotions could help cut heart health risks.

US researchers said their observational study was the first to show an independent relationship between positive emotions and coronary heart disease, but stressed that more work was needed before any treatment recommendations could be made.

"We desperately need rigourous clinical trials in this area. If the trials support our findings, then these results will be incredibly important in describing specifically what clinicians and/or patients could do to improve health," Karina Davidson of Columbia University Medical Center wrote in the study in the European Heart Journal.

Heart disease is the leading killer of men and women in Europe, the United States and most industrialised countries. Together with diabetes, cardiovascular diseases accounted for 32 percent of all deaths around the world in 2005, according to the World Health Organisation. Over ten years, Davidson and her team followed 1,739 men and women who were taking part in a large health survey in Canada. Trained nurses assessed the participants' heart disease risk and measured negative emotions like depression, hostility and anxiety, as well as positive emotions like joy, happiness, excitement, enthusiasm and contentment – collectively known as a "positive affect".

The researchers ranked the "positive affect" across five levels ranging from "none" to "extreme" and found that for each rank the risk of heart disease fell by 22 percent. Davidson, who led the research, said her findings suggested it might be possible to help prevent heart disease by enhancing people's positive emotions.