Increased CVD risk as a result of pneumonia or sepsis may persist for more than 5 years after infection.
While CVD risk began to fall after 1 year, it remained increased for more than 5 years after infection.
Lead study author Dr. Cecilia Bergh, of Oerebro University in Sweden, and colleagues recently reported their results in the European Journal of Preventive Cardiology.
Pneumonia is an infection characterized by inflammation of the air sacs in the lungs. Pneumonia is most commonly caused by bacteria called Streptococcus pneumoniae, thought it can be caused by a variety of other bacteria, viruses, fungi, and chemicals.
According to the Centers for Disease Control and Prevention (CDC), each year, around 1 million people in the United States seek hospital care as a result of pneumonia.
Sepsis is a life-threatening illness triggered by an overactive immune response to infections, including pneumonia and urinary tract infections. It is estimated that more than 1 million people in the U.S. are affected by sepsis every year.
Both pneumonia and sepsis have been associated with increased risk of CVD, which is an umbrella term for conditions that affect the heart and blood vessels, including heart disease, heart attack, and stroke.
However, Dr. Bergh and colleagues note that whether this increased risk persists for years after infection has been unclear. The researchers set out to address this uncertainty with their new study.
Greater CVD risk years after infection
The study involved 236,739 men, all of whom were born between 1952 and 1956. At the age of 18, the men underwent physical and psychological assessments. Data on the incidence of infection and CVD among the men were obtained from hospital registers, spanning from 1964 to 2010.
Using these data, the researchers looked at how hospital admissions due to pneumonia or sepsis influenced the risk of CVD at six different time points: up to 1 year after infection, 1 to 2 years after infection, 2 to 3 years after infection, 3 to 4 years after infection, 4 to 5 years after infection, and more than 5 years after infection.
A total of 46,755 men (19.7 percent) received a first CVD diagnosis during follow-up. Of these men, 8,534 received a diagnosis of sepsis or pneumonia, and there was a total of 9,987 hospital admissions as a result.
The team found that the highest risk of CVD was in the first year after hospital admission for pneumonia or sepsis, during which time a 6.33-fold increased risk was identified.
In the second year after infection, CVD was risk increased by 2.47 times, while a 2.12-fold risk was found in the third year after infection.
Although the risk of CVD reduced over time, the study revealed that there was still a 1.87-times greater CVD risk more than 5 years after infection.
When the researchers looked at the influence of hospital admission for pneumonia or sepsis on coronary heart disease, stroke, and fatal cardiovascular disease individually, similar results were found.
"Our results indicate that the risk of cardiovascular disease, including coronary heart disease and stroke, was increased after hospital admission for sepsis or pneumonia. The risk remained notably raised for 3 years after infection and was still nearly twofold after 5 years."
Dr. Cecilia Bergh
Findings suggest a causal relationship
The link between hospital admission for sepsis or pneumonia and increased CVD risk remained, but the results showed that the risk is highest in the first 3 years after infection.
"Conventional cardiovascular risk factors are still important but infection may be the primary source of risk for a limited time," notes study co-author Prof. Scott Montgomery, also of Oerebro University.
Overall, the researchers believe that their study suggests there is a causal relationship between pneumonia and sepsis and CVD, given that CVD risk is highest straight after infection and decreases over time.
The researchers speculate that this association may be down to the persistent systemic inflammation that occurs with severe infection, as this is a known risk factor for CVD. They note that although the majority of patients with pneumonia or sepsis make a full recovery, some patients may still have inflammatory markers circulating through their blood.
While the team did not look at any strategies that might reduce the CVD risk associated with pneumonia or sepsis, Prof. Montgomery believes that statin therapy should be investigated as a preventive strategy in future research.