Stress has been scientifically proven to cause heart attacks and strokes, according to ground-breaking new research.
The link between stress and cardiovascular problems has been a long-held belief among medical experts but, until now, there has been little physical evidence.
Now a US study has found that as well as increasing adrenaline, stress sends the immune system into overdrive by increasing the number of white blood cells that fight disease.
For people whose arteries are already thickened with plaque, extra white blood cells worsens inflammation and can lead to ruptures.
Platelets and clotting proteins then rush to fill the open wound – and if the clot fills the artery, it will cause a heart attack in a matter of moments.
Professor Matthias Nahrendorf, of Massachusetts General Hospital, Boston, working with colleagues from Harvard Medical School, analysed 29 medical staff exposed to chronic stress while working in an intensive care unit and found white blood cell counts rose in all of them.
The ‘challenging and fast paced environment’ was chosen as it frequently required life or death decisions to be made and the participants reported feeling their stress levels rose whenever they were on duty.
The researchers then looked at how chronic stress in healthy mice, induced by social or environmental factors such as isolation or tilting their cages, activated nerve fibres in their bone marrow.
This led to stem cell proliferation and increased white blood cell production.
Increased white blood cells appeared to induce hardening in the arteries, known medically as atherosclerosis, of the laboratory animals.
These resembled the ‘vulnerable lesions’ found in humans that are prone to rupture and cause heart attacks.
Prof Nahrendorf, whose findings were published in Nature Medicine, said: ‘When atherosclerosis-prone mice were subjected to chronic stress, accelerated (blood cell production) promoted plaque features associated with vulnerable lesions that cause (heart attack) and stroke in humans.
‘Taken together, these data provide further evidence of the hematopoietic system’s role in cardiovascular disease, and elucidate a direct biological link between chronic variable stress and chronic inflammation, a general concept with implications beyond atherosclerosis.’
The hematopoietic system is the bodily network of organs and tissues, primarily the bone marrow, spleen, tonsils, and lymph nodes, involved in the production of blood.