“Being happy is a great way to keep your heart healthy,” reported the Daily Express. The newspaper quotes doctors who say we should all put more fun in our lives to help avoid heart attacks.
The study assessed a range of symptoms such as depression, hostility, or anxiety in almost 2,000 men and women over 10 years. The participants’ reactions were recorded in videotaped interviews and scored on their joy, happiness, excitement and contentment on a five-point happiness scale. For each point higher up the scale a person was placed, their risk of developing heart disease dropped by 22%.
It is plausible that happier people are healthier. However, the actual effect demonstrated in this study was quite small, compared with the traditional modifiable risk factors, such as smoking, reducing blood pressure or bad cholesterol. These other factors can each independently reduce risk by more than a third, and the combined effect of improving these all together is much greater. In comparison, the one-point improvement on the happiness scale used here produces a relatively small, but probably still important, decrease in risk.
Where did the story come from?
This research was carried out by Dr Karina W Davidson and colleagues from the Center for Behavioral Cardiovascular Health at Columbia University Medical Center in New York. The study was supported by multiple grants from the National Institutes of Health (NIH), the National Center for Research Resources and the NIH Roadmap for Medical Research in the US. The paper was published in the peer-reviewed medical journal European Heart Journal.
Many newspapers reported this story and interpreted the science fairly, all emphasising the benefits of a range of positive emotions. Some, The Times for example, also quoted commentators who say this study does not prove ‘cause and effect’ and recommending that people should keep established risk factors, such as smoking, blood pressure and cholesterol under control too.
What kind of research was this?
This was an analysis of data from a prospective cohort study conducted in Nova Scotia, Canada. It aimed to see if positive emotions are linked with a lower risk of coronary heart disease (CHD). The researchers adjusted for several known heart risk factors and followed the population surveyed for up to 10 years. Only those who had completed the happiness questionnaires could be included in the analysis and the five-point happiness scale was only recorded at the start of the study. It is possible that these things will have led to some inaccuracies in the estimate of the degree of benefit that happiness apparently gives.
What did the research involve?
The researchers explain that previous studies have found a link between positive emotions and improved survival, immune function and a lower risk of diabetes and hypertension. They say negative emotions such as anger, hostility and depression are linked to a higher risk of a new episode of CHD.
The Canadian Nova Scotia Health Survey looked at the health of men and women 18 years of age and older in 1995 and followed them for the next 10 years. The main outcome of interest was heart disease and death. The researchers used hospital discharge codes or death certificates to assess new fatal or non-fatal cases of heart disease. They said that Nova Scotia has a universal healthcare insurance system and the computerised recording of health records is near complete.
Only residents who had attended the first clinic session and completed the structured interview were included. Anyone who had had a hospital discharge diagnoses of CHD in the five years prior to the start of the study was excluded.
The participants’ sex, age, total cholesterol, HDL cholesterol, blood pressure, history of diabetes and cigarette smoking were recorded at the beginning of the study, and a nurse measured their weight and height. From the collected data, the researchers took the records of 1,739 participants (862 men, 877 women) for analysis from the 5,576 original records in the survey.
The researchers then used a range of interview scales to score emotions:
- Depressive symptoms were measured using the Centers for Epidemiological Studies-Depressive symptoms (CES-D) scale, using 17 items from a 20-item self-reporting scale.
- Hostility was assessed with the Cook-Medley Hostility scale, involving 50 true–false items commonly used to assess self-reported hostility.
- Anxious symptoms were assessed using the Trait-subscale of the State-Trait Anxiety scale, a 20-item test that describes symptoms of anxiety (e.g. I worry too much over something that really does not matter).
- Positive affect (happiness) was scored using video of a 12-minute structured interview designed to be stressful. In the interview, researchers assess how participants express emotions and stress reactions. Positive affect is a rating of the degree to which the participant expresses positive emotions, whether verbally or in their behaviour (e.g. smiling) or tone of responses (e.g. cheerful). After the end of the interview the tapes were coded from one (no positive affect expressed) to five (extreme positive affect) by 23 certified coders.
What were the basic results?
The researchers adjusted their results for the traditional risk factors, including age, sex, blood pressure, cholesterol factors and for negatives affects such as depression and hostility, and found the rate of new episodes of CHD was 22% lower for a one-point increase in the positive affect score (adjusted hazard ratio [HR] 0.78, 95%, confidence interval [CI] 0.63 to 0.96).
When comparing people with high happiness scores to those with lower scores, those with higher scores were reportedly more likely to be female, less likely to be current smokers, and to have lower levels of total cholesterol, blood pressure, levels of hostility and anxious symptoms. The researchers say this, “suggests that higher levels of positive affect are related to better overall health”.
How did the researchers interpret the results?
The researchers say that in this large randomly selected sample, increased positive emotions (happiness) were associated with a reduced risk of new heart attacks over 10 years even after adjustment for depressive symptoms, hostility and anxiety.
They go on to say that the prospect that increasing happiness is associated with a decrease in the risk of heart disease is an exciting, but an untested theory that needs further research.
This study set out to test a theory that many people already accept without any strong evidence: that being happy is good for the heart. This research does appear to show that there is a link, at least in the context of a recorded interview as an assessment of happiness.
The researchers do caution that better heart health may just be related to better overall health in people who are happy. Some other limitations are also mentioned:
- As the information on cardiovascular risk factors was only measured at the start of the study, some misclassification is likely. Some people may have developed high blood pressure or started smoking during the 10 years of follow up.
- As the electronic records did not exist prior to 1990 it is technically possible that some participants who experienced CHD events more than five years before the study began could have been included in the analysis if they had also denied or forgotten their past heart disease.
- As an observational study, the researchers say they cannot rule out the possibility that things they did not measure or did not fully adjust for could be still causing the effect thought to be due to happiness. They say that those selected for the study were generally younger, female and less hostile than the participants who were excluded from the analysis. They say that it is “possible that our results may be at least partially accounted for by a selection bias”.
Overall, this study has provided useful data and illustrated the way that happiness can be measured relatively objectively in studies of emotions. The link is not completely clear and the fact that the confidence intervals in the statistical analysis were wide, suggests that if the selection bias is taken into account the effect of happiness might be quite small.
It is plausible that happier people are healthier. However, the actual effect demonstrated in this study was quite small, compared with the traditional modifiable risk factors, such as smoking, reducing blood pressure or bad cholesterol. These other factors can each independently reduce risk by more than a third and the combined effect of improving these all together is much greater. In comparison, the one point improvement on the happiness scale used here produces a relatively small, but probably still important, decrease in risk.