Outbursts of anger may trigger heart attacks, strokes and other cardiovascular problems in the two hours immediately afterwards, according to the first study to systematically evaluate previous research into the link between the extreme emotion and all cardiovascular outcomes.
The study - a systematic review and meta-analysis - published online today (Tuesday) in the European Heart Journal , found that in the two hours immediately after an angry outburst, a person's risk of a heart attack (myocardial infarction (MI) or acute coronary syndrome (ACS)) increased nearly five-fold (4.74%), the risk of stroke increased more than three-fold (3.62%), and the risk of ventricular arrhythmia also increased compared to other times when they were not angry.
The researchers found that the absolute risk increased if people had existing risk factors such as a previous history of cardiovascular problems, and the more frequently they were angry.
Dr Elizabeth Mostofsky (MPh, ScD), an instructor at the Harvard School of Public Health and a post-doctoral fellow in the cardiovascular epidemiological unit at Beth Israel Deaconess Medical Center, (Boston, USA), said: "Although the risk of experiencing an acute cardiovascular event with any single outburst of anger is relatively low, the risk can accumulate for people with frequent episodes of anger. This is particularly important for people who have higher risk due to other underlying risk factors or those who have already had a heart attack, stroke or diabetes. For example, a person without many risk factors for cardiovascular disease, who has only one episode of anger per month, has a very small additional risk, but a person with multiple risk factors or a history of heart attack or stroke, and who is frequently angry, has a much higher absolute excess risk accumulated over time."
Dr Mostofsky and her colleagues calculated that one extra heart attack (MI or ACS) per 10,000 people per year could be expected among people with low cardiovascular risk who were angry only once a month, but this increased to an extra four per 10,000 people with a high cardiovascular risk. However, among people who were frequently angry, five episodes of anger a day would result in around 158 extra heart attacks per 10,000 people with a low cardiovascular risk per year, increasing to around 657 extra heart attacks per 10,000 among those with a high cardiovascular risk.
The researchers say that their results do not necessarily indicate that anger causes the cardiovascular problems, only that they are associated with them. However, they say the results are fairly consistent across the studies even though they were conducted over a period of more than 18 years in different countries and groups of people. The studies used a case crossover design to compare each person's level of anger immediately before a cardiovascular event to anger levels at other times.
Led by Dr Murray Mittleman (MD, DrPH) who is director of the Cardiovascular Epidemiology Research Unit at Harvard Medical School, Associate Professor of Medicine and Epidemiology at the Harvard School of Public Health and a cardiologist at the CardioVascular Institute at Beth Israel Deaconess Medical Center, the researchers looked for studies carried out between January 1966 and June 2013 on the links between anger and a range of cardiovascular outcomes, and analysed results from nine that were eligible for meta-analysis. These included 4546 cases of MI, 462 cases of ACS, 590 case of ischaemic stroke, 215 cases of haemorrhagic stroke, and 306 cases of arrhythmia.
They found that there were numerous differences between the trials, including the country in which trials were conducted, the trial protocols and methodology. This meant that, although they brought the data from these trials together to produce combined estimates of increased risk, doing this was not always appropriate, although the evidence from all the studies pointed consistently towards a definite increased risk.
Dr Mostofsky said: "Previous studies have shown that outbursts of anger are associated with an immediately higher risk of cardiovascular events, including heart attack and stroke, but since some of these studies were based on small sample sizes with few patients having outbursts of anger, the results were often reported with low precision. Furthermore, there has been no systematic evaluation to compare the results and examine whether there is consistency across studies of the same cardiovascular outcome and whether the association is of similar magnitude across studies of different types of cardiovascular outcomes, for instance between a heart attack or a stroke. Despite the heterogeneity between the studies included in our meta-analysis, all of the studies found that compared to other times, there was a higher rate of cardiovascular events in the two hours following outbursts of anger."
The authors say there are several potential mechanisms linking anger outbursts and cardiovascular problems. "Psychological stress has been shown to increase heart rate and blood pressure, and vascular resistance," they write in their paper. Changes in blood flow can cause blood clots and may stimulate inflammatory responses.
Dr Mittleman said: "It is important to recognise that outbursts of anger are associated with higher risk of heart attacks, stroke and arrhythmia. If clinicians ask patients about their usual levels of anger and find that it is relatively high, they may want to consider suggesting either psychosocial or pharmacologic interventions. Regular use of statins and beta-blockers are known to lower long-term cardiovascular risk, which in turn lowers the risk from each episode of anger. However, further research is needed to evaluate whether specific medication use may help break the link between the anger episode and a cardiovascular event. In addition, some antidepressants may improve impulse control. Further research is needed to determine the effectiveness of psychosocial interventions to prevent cardiovascular events such as heart attack and stroke."
Now, he and his colleagues are investigating whether anger immediately before a heart attack has an effect on the long-term prognosis for the patient.
In an editorial on the paper, Dr Suzanne Arnold and Professor John Spertus (both from the University of Missouri - Kansas City, USA), and Dr Brahmajee Nallamothu (University of Michigan, USA), who were unconnected with the research, say that the link between anger and various cardiovascular conditions is well-ingrained in the minds of both clinicians and patients. However, "while the long-term link between chronic mental stress, anxiety, depression and hostility with adverse cardiovascular events has been well-established, it has been more difficult to determine the short-term risk of an acute outburst of anger," they write.
Despite the limitations caused by the problems of producing combined estimates from a small number of such varied studies, they say "as a systematic review, the manuscript highlights important, consistent findings of an increased risk of diverse cardiovascular events after an acute outburst of anger. Given the known physiologic effects of acute (and chronic) anger, these results are not surprising. The remaining question in all of these studies, however, is how to prevent these dangerous anger episodes."
They conclude: "Given the lessons we have learned from trying to treat depression after MI, treating anger in isolation is unlikely to be impactful. Instead, a broader and more comprehensive approach to treating acute and chronic mental stress, and its associated psychological stressors, is likely to be needed to heal a hostile heart."
 "Outbursts of anger as a trigger of acute cardiovascular events: a systematic review and meta-analysis", by Elizabeth Mostofsky, Elizabeth Anne Penner, and Murray A. Mittleman. European Heart Journal. doi:10.1093/eurheartj/ehu033
 "The hostile heart: anger as a trigger for acute cardiovascular events", by Suzanne V. Arnold, John A. Spertus, and Brahmajee K. Nallamothu. European Heart Journal, doi:10.1093/eurheartj/ehu097