Chronic stress: the hardest modifiable cardiovascular risk factor to control

Blood pressure is measured in millimetres of mercury (mmHg); cholesterol and glucose, in milligrams per decilitre (mg/dL). Smoking is counted in cigarettes, weight in kilos and a sedentary lifestyle in minutes of activity. Among the modifiable cardiovascular risk factors, chronic stress is the only one with no number, no pill and no clear target. That is why it is the hardest to control.

A useful alarm that never switches off

Acute stress is a useful, short-lived alarm response: the body gears up, deals with the problem and settles back down. Chronic stress sets in when there is no settling back: an excessive workload, caring for a relative, money worries, loneliness or a long-running conflict keeps that alarm sounding for weeks or months.

Keeping it on like that comes at a cost: allostatic load (the wear and tear the body accumulates from sustaining that response for longer than intended). An engine is not ruined by one burst of acceleration, but by being driven permanently over the rev limit.

This article is about prevention; if you are already living with coronary heart disease, read stress and emotional health in ischaemic heart disease.

What the evidence says: light and shade

The INTERHEART study compared 11,119 people who had had a first heart attack with 13,648 people who had not, from 52 countries. Stress was measured with four simple questions; those who reported permanent stress at work, at home or both had just over twice the odds of a heart attack (an odds ratio of 2.17). Psychosocial factors taken together (stress, depression and others) were estimated to account for 32.5% of heart attacks in the population, compared with 35.7% for smoking and 17.9% for high blood pressure.

Those figures come with small print. INTERHEART asked about stress after the heart attack, when the preceding months tend to be remembered as tougher (recall bias). Studies that measure stress first and then watch what happens find more modest effects. One of the largest, a pooled analysis of 13 European studies covering 197,473 workers followed for an average of 7.5 years, found that job strain (high demands with little control over one's work) was associated with a 23% higher risk of coronary heart disease, and attributed 3.4% of cases to it. According to its authors, preventing job strain could reduce the number of cases, but far less than acting on classic risk factors such as smoking.

Both things are true: chronic stress is a genuine risk factor, but its exact weight is harder to measure than that of blood pressure or cholesterol.

From brain to artery

An imaging study followed 293 people without cardiovascular disease for almost four years: greater activity in the amygdala (the region of the brain involved in the stress response) was associated with more bone marrow activity, more arterial inflammation and more cardiovascular events. With only 22 events, it points to a plausible mechanism rather than offering definitive proof.

Better-known pathways add to this: sustained activation of the sympathetic nervous system (the body's "accelerator") and the continued release of cortisol (the main stress hormone) help to raise blood pressure, promote insulin resistance (the forerunner of type 2 diabetes) and abdominal fat, and reduce heart rate variability. And there is an indirect one: poorer sleep, more smoking and alcohol, a poorer diet, less exercise and poorer adherence to treatment.

Why it is the hardest factor to control

The difficulty is not that it is the most harmful, but that it slips past the tools used to control the others. Six reasons explain why.

It has no number

There is no equivalent of the mmHg used for blood pressure or the mg/dL used for cholesterol. Stress is assessed through interview and questionnaires, and there is no validated laboratory test for measuring it in routine clinical practice. Without a number there is no target and no simple way of knowing whether things are improving: nobody receives a report that says "your stress has come down by twenty points".

It has no pill

No drug exists that "lowers stress" and has been shown, by doing so, to reduce heart attacks. With cholesterol or blood pressure the opposite is true: there are treatments that bring the number down and, in doing so, prevent heart attacks. That takes nothing away from the treatment of anxiety or depression when it is indicated, nor is it a reason to stop it.

Its cause is often not entirely in your hands

An impossible shift pattern, a debt or a relative with dementia cannot be resolved by willpower. Giving up smoking, however hard, is your own decision; changing your working conditions often is not. That is why the classic "just take things easier" is as useless as it is unfair.

It is normalised, even admired

We tend to mistake it for productivity or commitment: an overflowing diary sounds like a virtue. Nobody boasts about having high blood pressure, but plenty boast about never stopping. And because it does not hurt, it is always left for later.

It sabotages control of the other factors

Anyone living on constant alert finds it harder to bring down blood pressure, weight or glucose, to give up smoking and to take medication consistently. Stress does not only add risk: it also complicates precisely the things that can be fixed.

Perception adapts

After months on alert, what was once exceptional becomes "normal", and you say in all sincerity that you are fine. No longer noticing it does not mean it has gone away: the body may still be showing the strain in blood pressure, sleep or pulse.

What does work, and how strong the evidence is

Difficult does not mean untreatable, although not every measure has the same backing. The best supported is regular physical exercise, which acts on stress and on cardiovascular risk at the same time. Getting enough sleep counts too. Cognitive behavioural therapy (a type of psychotherapy focused on changing thoughts and behaviours) and structured stress management programmes relieve distress, although it is less well established that they prevent heart attacks; relaxation and meditation are useful as a complement, with more modest evidence. Social support cushions the load and, where the source of the stress can be changed, changing it tackles the problem at its root.

And the key point: because stress cannot be measured or treated with precision, it makes sense to control more rigorously the factors that do have a number and a treatment, just as with an inherited and barely modifiable factor such as lipoprotein(a).

What a cardiology assessment adds

The role of cardiology is not to measure stress, but to measure what stress may be disrupting. Overall cardiovascular risk is estimated and blood tests are requested. With 24-hour ambulatory blood pressure monitoring (ABPM), it is possible to uncover masked high blood pressure (masked hypertension): readings that are normal in the clinic but raised over the course of the day. If there are palpitations, an electrocardiogram or a Holter monitor (a continuous recording of the heart rhythm over 24 hours or more) is added.

Asking about stress is part of a complete assessment: the cardiovascular prevention guideline of the European Society of Cardiology (ESC, 2021) regards it as a risk modifier, with a dose-response pattern (the more stress, the greater the risk), and says that assessing it should be considered.

Naming it is the first step

The fact that chronic stress has no number and no pill does not make it a minor matter, nor the fault of the person living with it. It calls for a different strategy: recognising it, not accepting it as normal and taking better care of what can be measured. Here too, the best medicine is good prevention.

Sources and further reading

• Rosengren A, et al. INTERHEART study: psychosocial risk factors and risk of acute myocardial infarction in 52 countries. The Lancet, 2004
• European Society of Cardiology: 2021 Guidelines on cardiovascular disease prevention in clinical practice
• British Heart Foundation: stress and your heart

This article is for information only and does not replace individual assessment or advice from a healthcare professional. For acute symptoms such as severe chest pain, call 112.