Aspirin associated with improved survival in patients with severe pneumonia

"The old drug acetylsalicylic acid, better known as aspirin, seems to have a strong and statistically significant association with improved survival in patients diagnosed with serious cases of the most common form of bacterial pneumonia, caused by the bacteria Steptoccus pneumoniae," says Magnús Gottfreðsson, professor of infectious diseases at the University of Iceland and senior consultant at Landspítali University Hospital, explaining the findings of a new study by scientists at UI and Landspítali. The paper presenting these findings has been published in the respected Journal of Internal Medicine. The paper is based on the research of Kristján Godsk Rögnvaldsson, a PhD student at the UI Faculty of Medicine and a doctor at Landspítali University Hospital. Magnús Gottfreðsson is his PhD supervisor.  

Besides Magnús and Kristján, the authors of the paper are: Agnar Bjarnason, doctor and lecturer at the Faculty of Medicine; Karl Kristinsson, doctor; Hörður Tryggvi Bragason, medical student at UI; Helga Erlendsdóttir, biomedical scientist; and Guðmundur Þorgeirsson, doctor and professor emeritus at UI. 

"This protective effect was apparent immediately and in fact was strongest during the acute phase of infection, which is when the risk of complications such as heart failure and coronary thrombosis peaks and mortality is high. But the effect lasted for an entire year and probably longer, which is remarkable. This applies to patients who take aspirin after becoming ill, even after adjusting for potential bias," says Magnús. 

Nationwide research cohort 

Magnús and Kristján say that the unique aspect of the study is that in Iceland it is possible to look at a very large group of patients infected with the same bacteria and monitor them long term. They explain that they used a nationwide cohort over a period of 45 years, looking at survival up to 1 year after infection. The study uses data from a total of 815 cases of infection.

"By going over all available medical records in Iceland, we could avoid focusing on particular groups of patients while overlooking others, which is a common problem in foreign research and one that makes it harder to extrapolate findings to a larger group," says Magnús. He adds that aspirin is sold without a prescription and many people take it without consulting a doctor. 

"This means it is not feasible to conduct research like this simply by looking at prescriptions or pharmacy dispensations. It is also remarkable to see such a strong effect, since aspirin is a very cheap and accessible treatment."

Solution to a major problem?

Magnús and Kristján say that it is always nice to see the results of your  research, especially if the wait has been long and the findings are exciting. 

"It's wonderful to be able to share them with the scientific community. This is a study that actually began over 15 years ago. It has taken a long time to collect all the data and a lot of people have contributed towards making the project a reality. The publication venue is also important, of course, and the Journal of Internal Medicine is a highly respected medical journal, established in 1863. We published the article in open access to ensure that our findings would be accessible to everyone and we hope they will encourage further research and collaboration."

They explain that it is too early to say whether they have identified a solution to a major problem and not yet appropriate to advise everyone diagnosed with pneumonia to take aspirin in addition to other treatments. However, there are certainly grounds to conduct treatment trials.

Patients on aspirin have significantly better survival rates

Magnús and Kristján explain that this is a retrospective study covering all cases of patients admitted to hospital with pneumonia and sepsis caused by the bacteria Streptococcus pneumoniae between 1975 and 2019. 
"We compared mortality between patients that were taking aspirin on admission and those that weren't. We corrected for differences between groups using inverse probability weighting and compared survival rates using a statistical method called Cox regression. Patients who were on aspirin turned out to have significantly better survival rates 90 days and 1 year after infection, compared to if they had not been taking the drug. It is interesting to note that the biggest difference is apparent in the very first days following infection," explains Kristján.

Kristján says that this study suggests that aspirin has a protective effect among patients dealing with serious infections caused by Streptococcus pneumoniae. "It is important to caveat this by making clear that this was not a randomised treatment trial and there could be some underlying factor that we failed to correct for that explains the results. Further research is required in order to confirm or disprove our findings."
The research team and the authors of the article suggest that a randomised double-blind trial should be conducted on pneumonia patients at increased risk of cardiovascular disease. 
The article in the Journal of Internal Medicine is based on research by Kristján Godsk Rögnvaldsson, a PhD student at the UI Faculty of Medicine and doctor at Landspítali University Hospital. Magnús Gottfreðsson is his PhD supervisor.