Chronic stress from people's everyday lives may be causing lasting structural changes to the heart, harming health and reducing life expectancy.
The findings come from a study of almost half a million adults in the UK, believed to be the largest of its kind, led by researchers at the MRC Laboratory of Medical Sciences (LMS) and Imperial College London.
It finds that chronic inflammation, associated with people's socioeconomic situation and lifestyles, is linked to damaging structural changes in the heart, as well as to a higher risk of heart attacks and stroke.
The researchers explain that these changes may appear years before people experience any cardiovascular symptoms, remaining a hidden health threat.
Professor Declan O'Regan, British Heart Foundation Chair of Cardiovascular AI at Imperial College London and Head of the Computational Cardiac Imaging Group at the LMS, said: "Our study, which is the largest of its kind, suggests that millions of people could be living with hidden inflammation, which is slowly changing their heart and causing long term damage - increasing the risk of heart attack and stroke. Chronic inflammation is complicated, but we know it's tied to our health and driven by a range of lifestyle and economic factors – meaning people may be at more risk just because of their surroundings, their economic status, their family's health and their lifestyle."
"But while tackling health inequalities remains an issue, there are things that we can do about inflammation, including reducing risk factors like smoking and obesity."
Chronic inflammation is a long-term low-level activation of the body's immune system. It has been linked with a range of diseases, including cancer and diabetes, and is increasingly recognised as a hidden driver of heart disease.
In the latest study, researchers analysed UK Biobank data from nearly 480,000 UK adults. They used a blood marker known as glycoprotein acetyls (GlycA), alongside heart imaging and genetic data.
They found that people with the highest levels of inflammation (the top 20%) had a 43% higher risk of heart attack and stroke than those with the lowest levels (the bottom 20%). But in addition, those with higher levels also showed more evidence of structural changes in their hearts, including thickened heart walls, smaller heart chambers and poorer heart filling – all changes which may develop quietly for years before progressing to heart failure.
Higher levels of inflammation were strongly associated with measures of socioeconomic disadvantage and psychological distress, as well as the more established risk factors including smoking and excess body fat.
People with persistently higher levels of inflammation in the study faced a 43% greater risk of heart attack and stroke, even if they had no previously existing heart disease.
The findings suggest that chronic inflammation may be one biological pathway through which everyday life stresses, including poverty and mental health issues can have biological effects that may increase cardiovascular risk.
Professor Declan O'Regan added; "The surprising thing was how much social factors and mental health are linked to inflammation and damage to the heart - as well as more well-known risk factors like smoking and inactivity. There was also a strong genetic factor, with some people being naturally more resilient or susceptible to the inflammatory damage that comes from different lifestyles."
However, the researchers stress that people who are genetically susceptible or exposed to adverse circumstances are not destined to develop heart disease, and much can be done to prevent long term inflammation.
The study identified key inflammatory proteins from the interleukin-1 and TNF families as likely drivers of this damage. Several of these proteins are already being targeted by drugs in clinical trials, raising hopes that anti-inflammatory treatments could help prevent cardiovascular disease before symptoms appear.
The findings suggest that combining inflammation blood tests with genetic risk scores could help identify those most likely to benefit from early intervention.
Professor Bryan Williams, Chief Scientific and Medical Officer at the British Heart Foundation, said: "Inflammation is part of the body's healing process, but there is also a darker side to it. This large-scale study found people with higher levels of inflammation experienced silent changes to the structure of their hearts and had a higher risk of major cardiac events including heart attacks and strokes."
"The research provides valuable insights into how our genes and lifestyle factors, such as smoking, poor mental health and socioeconomic status, can converge to trigger inflammation. It also identifies several inflammatory proteins that appear to play a key role in the heart changes linked to chronic inflammation, and it is to be hoped that anti-inflammatory medicines could become an important tool in preventing cardiovascular disease.
"These findings reinforce the importance of tackling the causes of inflammation and poor cardiovascular health, while also supporting people to make lifestyle changes that can help protect their hearts."
The study was funded by the Medical Research Council and British Heart Foundation.
The work was also supported by the NIHR Imperial Biomedical Research Centre , a translational research partnership between Imperial College Healthcare NHS Trust and Imperial College London.
