Researchers at the University of Oulu have identified genes that increase susceptibility to pneumonia. Alongside inherited risk factors, smoking and higher body mass were also found to raise the risk of developing the disease.

The study identified a total of 12 genetic regions associated with pneumonia risk, eight of which were identified for the first time. Many of these regions are linked to the regulation of the body’s inflammatory response. However, among patients with recurrent pneumonia and among older patients, genes associated with nicotine dependence played a particularly prominent role.

The researchers also used genetic data to assess causal relationships. The findings provide evidence that smoking and obesity may increase the risk of pneumonia through a direct cause-and-effect relationship.

The study was conducted by analysing genetic and health data from more than 600,000 individuals in Finland and Estonia. Genetic risk factors for pneumonia were examined not only in the general population, but also across three age groups, among people with recurrent pneumonia, and among individuals with asthma.

“The strength of the study lies in its large and reliable dataset, which combines genetic information with long-term health data from two countries. This also made it possible to examine genetic risk factors for pneumonia across different age groups and patient populations,” says Doctoral Researcher Anni Heikkilä, who served as the study’s lead analyst.

Pneumonia is a major infectious disease and a significant cause of mortality. In Finland, around 50,000 people develop pneumonia each year, and approximately half of them require hospital treatment. The disease can be caused by bacteria, viruses or, more rarely, fungi, and its severity ranges from mild to severe depending on both the patient and the causative agent.

The incidence of pneumonia is markedly higher than average in certain population groups. Those at greatest risk include older people, individuals with chronic heart and respiratory diseases, immunocompromised patients, as well as heavy alcohol users and smokers. In addition, socioeconomic factors and certain long-term conditions increase the risk of illness, making prevention and early treatment particularly important in these groups.

“Understanding inherited risk factors helps to clarify why some individuals are more susceptible to pneumonia and how the disease progresses. The association between genes related to nicotine dependence and pneumonia risk in older adults is a finding of considerable public health importance. In the future, our results may be used to support the development of treatments and to improve disease prevention,” emphasises Professor Timo Hautala, an infectious diseases specialist at the University of Oulu and Oulu University Hospital.

The study has recently been published in the scientific journal eBioMedicine: Anni Heikkilä, Eeva Sliz, Sara Väyrynen, Kadri Reis, Abdelrahman G. Elnahas, Anu Reigo, Tõnu Esko, Johannes Kettunen, Timo Hautala, Genetic risk factors for pneumonia differ by patient subgroup, eBioMedicine, Volume 124, 2026.