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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

People with pneumonia are at high risk of having a heart attack or stroke. New research suggests that taking aspirin may reduce the risk of these cardiovascular events.

Pneumonia is swelling (inflammation) of the tissue in one or both lungs. It is usually caused by bacterial infection but can also be caused by viruses, including coronavirus.

This large observational study was based on a primary care database. It found that people taking aspirin had a lower risk of cardiovascular events after pneumonia than those not taking aspirin.  The researchers suggest that a randomised, controlled trial is warranted to investigate this relationship further.

What’s the issue?

Approximately 100,000 people in the UK develop pneumonia each year. Symptoms include difficulty breathing, a cough, rapid heartbeat and high temperature. Chest pain may get worse when breathing or coughing.

Heart attacks and strokes are common after pneumonia, and can be fatal.  Aspirin has been suggested as a potential therapy to reduce these cardiovascular events. However, previous trials have been small. This observational study was the largest to date.

What’s new?

The researchers used a large database of UK primary care patients to find more than 48,000 people aged over 50 who had been diagnosed with pneumonia. They identified 8,099 people who were taking aspirin in the months before they were diagnosed with pneumonia. Each aspirin-user was matched with a non-aspirin user of similar age, gender, smoking habit, and history of cardiovascular disease. The two groups were then compared.

The results showed that the risk of ischemic stroke and heart attack in the six months following pneumonia diagnosis was one-third lower among aspirin users. This finding was the same in additional analyses using different statistical methods.

To check that the reduction in cardiovascular effects was specifically related to aspirin, the researchers looked at other drugs taken by the people in the study. They included the painkiller paracetamol; a drug for treating underactive thyroid gland (levothyroxine); other drugs in the same class as aspirin (non-steroidal anti-inflammatory drugs); and drugs to reduce acid in the stomach (protein pump inhibitors). These other drugs either showed no effect on rates of cardiovascular events after pneumonia, or actually increased the risk.

Why is this important?

This study suggests that aspirin could prevent cardiovascular complications in pneumonia. Pneumonia is common and any reduction in the risk of cardiovascular events could prevent many deaths.

What’s next?

The results of this study lay the foundation for a randomised, controlled trial. The researchers have applied for funding for this trial and hope to run it over the next few years. If this trial confirms that aspirin is beneficial for pneumonia patients, it could lead to changes in practice.

Further research is also needed to increase understanding of cardiovascular events in pneumonia, why they happen and how aspirin works to reduce risk.

You may be interested to read

The full paper: Hamilton F, and others.  Aspirin reduces cardiovascular events in patients with pneumonia: a prior event rate ratio analysis in a large primary care database. Eur Respir J. 2020. doi: 10.1183/13993003.02795-2020

A paper from over 10 years ago that initially demonstrated the issue of cardiovascular events after infection: Smeeth L, and others. Risk of Myocardial Infarction and Stroke after Acute Infection or Vaccination. The New England Journal of Medicine. 2004;351:2611–18

A subsequent review article that clearly defines the issue: Musher DM and others. Acute Infection and Myocardial Infarction. The New England Journal of Medicine. 2019;380:171–76


Funding: The work was funded through the NIHR Academic Clinical Fellowship, NIHR Doctoral training fellowship and NIHR Applied Research Collaboration South West Peninsula. The study was supported by the NIHR Health Protection Research Unit in Evaluation of Interventions. The author received various grants from NIHR HSDR and from NIHR School of Primary Care Research to support research safe and effective use of medicines.

Conflicts of Interest: One author has received fees from a pharmaceutical company and a software company.

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