Nikhil Prasad Fact checked by:Thailand Medical News Team Jun 07, 2026 1 hour, 32 minutes ago
Medical News: A common bacterium best known for causing respiratory infections may also be quietly increasing the risk of heart attacks, according to a new study that is reigniting debate about the hidden role of chronic infections in cardiovascular disease.
Researchers find that past exposure to a common respiratory bacterium is significantly more common among patients
suffering acute heart-related emergencies.
Researchers have discovered that people suffering from acute coronary syndromes (ACS), a group of life-threatening heart conditions that includes heart attacks and unstable angina, were significantly more likely to show evidence of previous infection with Chlamydia pneumoniae. The findings suggest that long-term exposure to the bacterium could be linked to the development of dangerous arterial disease, although scientists caution that the relationship is not yet proven to be causal.
The study was conducted by researchers from the College of Medicine, Alfaisal University, Riyadh, Saudi Arabia; the College of Medicine, Alexandria University, Alexandria, Egypt; and the Department of Biochemistry and Molecular Medicine, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia.
A Missing Piece in Heart Disease?
For decades, doctors have focused on traditional cardiovascular risk factors such as smoking, high blood pressure, diabetes, obesity, and high cholesterol. While these factors explain a large proportion of heart disease cases, they do not account for all patients who experience heart attacks.
This has led scientists to investigate whether chronic infections and ongoing inflammation may play a role in accelerating damage to blood vessels.
Chlamydia pneumoniae is a widespread bacterium responsible for many cases of respiratory tract infections and pneumonia. Most adults have been exposed to it at some point in their lives. Previous studies have detected the bacterium in atherosclerotic plaques, raising suspicions that it could contribute to the buildup of fatty deposits inside arteries.
Examining Patients with Acute Coronary Syndromes
To investigate the connection, researchers recruited 100 participants from Alexandria University Hospital in Egypt. The study included 47 patients diagnosed with acute coronary syndromes and 53 healthy individuals who served as controls.
Among the ACS patients, 29 had experienced acute myocardial infarction, commonly known as a heart attack, while 18 had unstable angina, a condition caused by reduced blood flow to the heart that often precedes a major cardiac event.
Blood samples were analyzed for antibodies against Chlamydia pneumoniae. The researchers specifically measured IgG antibodies, which indicate past or chronic infection, and IgM antibodies, which indicate a recent or active infection.
Higher Infection Rates Found in Heart Patients
The results revealed a striking difference between the two groups. Evidence of previous Chlamydia pneumoniae infection was found in 83 percent of ACS patients compared with 60.4 percent of healthy controls. Statistical analysis showed th
at individuals carrying these antibodies were significantly more likely to belong to the heart disease group.
Importantly, no participant tested positive for IgM antibodies, indicating that none of the subjects had an active infection at the time of the study. This suggests that any potential cardiovascular effects are linked to chronic or past exposure rather than an acute respiratory illness.
Even after adjusting for major cardiovascular risk factors such as smoking, hypertension, diabetes, and dyslipidemia, the association between Chlamydia pneumoniae exposure and acute coronary syndromes remained evident.
Inflammation Emerges as a Major Factor
Researchers also measured levels of C-reactive protein (CRP), a marker widely used to assess inflammation within the body.
Nearly 94 percent of ACS patients had elevated CRP levels, while none of the healthy controls showed increased levels. This confirms the powerful inflammatory response associated with acute cardiac events.
However, the researchers found no meaningful difference in CRP levels between ACS patients who were positive for Chlamydia pneumoniae antibodies and those who were not. This indicates that while inflammation is strongly linked to heart attacks, the bacterium itself may not be directly responsible for triggering the inflammatory surge observed during an acute event.
This
Medical News report highlights that the findings support a growing theory that chronic infections may help create a long-term inflammatory environment that promotes atherosclerosis rather than directly causing a heart attack.
Why the Findings Matter
Scientists have long suspected that infectious organisms might contribute to cardiovascular disease by damaging blood vessel walls, promoting inflammation, encouraging cholesterol accumulation, and accelerating plaque formation.
Laboratory studies have shown that Chlamydia pneumoniae can infect endothelial cells, smooth muscle cells, and immune cells found within blood vessels. Such infections may promote oxidative stress and inflammatory signaling that gradually weaken arterial health over many years.
Yet despite these observations, previous large clinical trials using antibiotics to target the bacterium failed to reduce cardiovascular events. This remains one of the strongest arguments against the idea that the bacterium is a direct cause of heart disease.
Conclusions
The new study adds to mounting evidence that chronic Chlamydia pneumoniae infection may be associated with an increased risk of acute coronary syndromes. While the researchers found significantly higher rates of past infection among heart patients, the results do not prove that the bacterium directly causes heart attacks. Instead, the findings suggest that the microorganism may contribute to a broader inflammatory environment that supports the development and progression of atherosclerosis. Larger studies using direct pathogen detection techniques will be needed to determine whether Chlamydia pneumoniae is an active participant in cardiovascular disease or simply a marker of individuals already at higher risk. Until then, traditional risk factors such as diabetes, hypertension, smoking, and cholesterol abnormalities remain the primary targets for preventing heart attacks and other serious cardiovascular events.
The study findings were published in the peer reviewed journal: Medicina.
https://www.mdpi.com/1648-9144/62/6/1107
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