A hidden blow to the heart: what is the danger of chronic inflammation
A high level of chronic inflammation was associated with changes in the structure of the heart, which can develop for years without noticeable symptoms and precede heart failure. Participants with the highest levels of inflammation had a 43% higher risk of serious cardiovascular events than those with the lowest values. How stress, smoking, financial situation and genetics are related to inflammation and whether it is possible to detect a hidden threat before symptoms appear — in the "Izvestia" material.
How chronic inflammation changes the heart
Inflammation is a natural defense reaction of the body. It helps the immune system fight infections, repair damaged tissues, and respond to injury. Usually, after the threat is eliminated, the inflammatory reaction weakens.
However, sometimes the immune system remains in a state of prolonged activation. Such chronic inflammation can occur without fever, pain, or other noticeable symptoms. At the same time, substances related to the functioning of the immune system remain in the blood for a long time.
Chronic inflammation has previously been associated with diabetes, cancer, and cardiovascular diseases. In a new study, specialists from the Laboratory of Medical Sciences of the British Medical Research Council and Imperial College London decided to establish how it relates to the structure of the heart, the risk of heart attack, stroke and heart failure.
The authors used data from the British biobank UK Biobank. The main sample included 488,079 people who were between 40 and 69 years old at the time of joining the project. The researchers compared the results of blood tests, magnetic resonance imaging of the heart, electrocardiography, genetic testing and information about the participants' lifestyle.
The condition of people was monitored for an average of more than 15 years. During this time, 74,336 participants had serious cardiovascular events, including heart attack, stroke, heart failure, cardiac arrest, or death from cardiovascular disease.
How scientists measured latent inflammation
To assess chronic inflammation, the researchers used the GlycA index — the content of acetylated glycoproteins in the blood. It was determined by nuclear magnetic resonance spectroscopy.
GlycA is not one specific protein. This indicator reflects the combined signal from several acute phase proteins, the concentration of which changes when the immune system is activated. Unlike some other markers, GlycA is considered relatively stable and may better reflect prolonged inflammation rather than a short-term reaction to infection or injury.
The authors also compared it with highly sensitive C-reactive protein, a more common indicator of inflammation. The addition of GlycA to the model, which already took into account C-reactive protein and traditional cardiovascular risk factors, slightly improved the prediction of complications.
However, GlycA analysis is not yet included in the standard medical examination. The authors of the study emphasize that its practical benefits need to be confirmed in other population groups and individual prospective trials.
What changes were found in the heart
The relationship between the level of inflammation and the structure of the heart was studied in 70,809 participants who underwent magnetic resonance imaging and electrocardiography.
In people with higher GlycA levels, the volume of the chambers of the heart was on average smaller, and its walls were relatively thicker. Scientists also found a decrease in the volume of blood that the heart releases in one contraction, and signs of impaired diastolic function — the ability of the heart muscle to relax and fill with blood.
These changes were accompanied by a compensatory increase in heart rate. In other words, with a decrease in the volume of blood released in one contraction, the body might need to increase its heart rate to maintain blood circulation.
Such a restructuring does not mean that a person will necessarily develop heart failure. Nevertheless, the combination of thickened walls, reduced chambers, and impaired filling is considered an unfavorable option for heart remodeling, which can occur long before the symptoms are pronounced.
"Millions of people can live with latent inflammation that gradually changes the heart and causes long—term damage," said Declan O'Regan, head of the computer heart imaging group at the Laboratory of Medical Sciences, Professor at Imperial College London.
How much did the risk of heart attack and stroke increase
The participants were divided into five groups depending on the GlycA level. People in the top fifth of the distribution had a 43% higher risk of a serious cardiovascular event than those in the group with the lowest levels of inflammation.
We are talking about relative, not absolute risk. This indicator does not mean that 43% of people with elevated GlycA had a heart attack or stroke. It shows the difference between the two groups after taking into account a number of other factors.
In addition, the study was observational. It revealed a stable link between inflammation, changes in the structure of the heart and subsequent cardiovascular events, but does not prove that an increase in GlycA directly caused all the detected disorders.
After additional consideration of the C-reactive protein level, the bond value decreased. This indicates that GlycA partially reflects the same inflammatory processes as other biomarkers. Nevertheless, it retained its independent predictive value in statistical models.
What does chronic stress have to do with it
In total, experts studied 169 external factors and eight indicators of body composition. The amount of adipose tissue in the trunk area, smoking, psychological distress and socio-economic disadvantage were most strongly associated with an increased level of inflammation.
Psychological distress is a state of prolonged emotional stress that can manifest itself as anxiety, depression, irritability, and a feeling of inability to cope with stress. It is close to the everyday concept of chronic stress, but it is not completely equal to it.
At the same time, socio-economic conditions do not operate in isolation. They can affect the quality of nutrition, access to medical care, physical activity, pollution levels, sleep duration, and the likelihood of smoking. It is difficult to separate the influence of each factor in an observational study.
What role does heredity play?
The scientists also analyzed polygenic risk indicators — a set of multiple genetic variants, each of which makes a small contribution to the likelihood of a particular disease.
The results showed that hereditary features can change the strength of the body's response to external factors. With the same level of smoking, psychological distress, or excess adipose tissue, the inflammatory response may vary from person to person.
This may partly explain why some people remain relatively healthy for a long time in the presence of risk factors, while others develop cardiovascular disorders faster.
However, a genetic predisposition does not mean an inevitable disease. Polygenic indicators reflect probability, not a predefined scenario. A significant part of the discovered factors — smoking, physical activity and the amount of adipose tissue — are potentially amenable to change.
In addition, about 95% of the study participants identified themselves as a white ethnic group. Therefore, the obtained genetic results cannot be automatically transferred to all population groups without additional verification.
Which proteins can damage the heart
To understand the possible mechanisms, the researchers studied 80 proteins involved in inflammatory processes. The signaling pathways of interleukin-1, tumor necrosis factor, and interleukin-6 played the most prominent role.
One of the main candidates was an interleukin-1 receptor antagonist. According to statistical analysis, it could mediate about 27% of the relationship between GlycA levels and a decrease in the final diastolic volume of the left ventricle — the amount of blood in its cavity before contraction.
A total of 63 proteins statistically mediated the association between GlycA and cardiovascular events. However, such an analysis does not confirm that each of them directly causes damage. The authors themselves call these results preliminary, since the concentration of the inflammatory marker, proteins, and some heart parameters were evaluated without the necessary time separation.
Some of the identified signaling pathways are already being studied in clinical trials of anti-inflammatory drugs. In particular, the researchers are considering drugs that affect interleukin-6 and interleukin-1. This makes it possible in the future to more accurately identify the groups of patients who may benefit from anti-inflammatory therapy.
However, the results do not mean that such drugs can already be used for prevention in all people with elevated inflammation. Previously, some anti-inflammatory approaches reduced the risk of recurrent complications in patients after a heart attack, while others did not improve the condition of patients with heart failure. Efficacy and safety depend on the specific drug, the inflammatory pathway, and the patient group.
Is it possible to detect the risk before the symptoms appear
The authors suggest that combining tests for inflammatory markers with genetic risk indicators in the future may help identify people who need early prevention. However, such a scheme is not yet ready for mass use.
To implement the method, it is necessary to check how accurately it predicts heart attack, stroke and heart failure compared to the tools already used. It is also important to establish whether early detection of elevated GlycA improves treatment outcomes, rather than just adding risk information.
Today, when assessing the condition of the heart, doctors primarily take into account blood pressure, cholesterol and glucose levels, body weight, smoking, physical activity, age, family history and the presence of concomitant diseases.
According to the World Health Organization, a significant part of cardiovascular diseases can be prevented by quitting tobacco, regular physical activity, a balanced diet, alcohol restriction and weight control. At the same time, responsibility cannot be completely shifted to the individual himself: the availability of a healthy diet, a safe environment, medical care and opportunities for physical activity also depends on social conditions.
Переведено сервисом «Яндекс Переводчик»
