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Many of us believe stress can cause stroke, but the evidence linking the two is not as clear as you might think.
Many of us are plagued by stress. It can affect our sleep, work and relationships, as well as our mental and physical health. But can stress increase your risk of having a stroke?
Stress and stroke are often linked together anecdotally, but studying this connection is notoriously difficult.
Conducting randomised controlled trials – the so-called gold standard in terms of research – is problematic, because of the ethical issues involved with researchers inflicting stress on one group of people so they can compare results to another group. And of the data that is available, much comes from case control studies, which rely on interviews with people who have recently had a stroke, providing researchers with information that can be inaccurate.
A stroke occurs when an artery in or near the brain is either blocked, cutting blood supply to brain tissue, or bursts, causing a bleed. After heart disease, stroke is the second biggest killer in Australia.
Professor Graeme Hankey, head of the Stroke Unit at Royal Perth Hospital, says chronic stress is emerging as a risk factor for stroke, albeit a weak one.
In a recent Spanish study, researchers interviewed 150 people who’d had a stroke. Participants who reported experiencing stressful life events in the previous year had almost four times the risk of having a stroke when compared with a similar group of people – who lived in the same neighbourhood and were about the same age – who didn’t have strokes.
Professor Craig Anderson, professor of stroke medicine and clinical neuroscience at The George Institute for Global Health, says the study’s findings were “reasonable”. However, he points out it was a small study that relies on interviews with participants who have recently had a stroke.
“People recall things differently after the event compared with controls when they’re well… you never fully eliminate the fact patients behave differently after an event so there’s likely to be an over-reporting of stressful events,” he says.
Also the average age of people in the study was about 54, whereas more than half of strokes occur in people 75 or older, and researchers also did not include patients with severe stroke who were unable to communicate.
Anderson’s own 2010 research looked at people who had subarachnoid haemorrhage – the most lethal type of stroke – and found no relationship between the stroke and stressful life events.
In his view, rather than stress directly causing stroke, it may exacerbate existing symptoms.
But Hankey says this study, when viewed alongside other research, suggests chronic stress could be a risk factor for stroke. But whether it is a direct cause is still uncertain.
In the INTERSTROKE study, which looked at 6000 people from 22 countries, stress is identified as one of 10 modifiable risk factors that account for 90 per cent of strokes worldwide.
The risk factors INTERSTROKE identified include:
hypertension – high blood pressure
low physical activity
cardiac causes such as atrial fibrillation, previous heart attack and valve disease
psychological factors including stress and depression
Each of these factors carries a different level of risk, with roughly a third of all strokes being attributable to high blood, while stress was linked in less than 5 per cent.
“The INTERSTROKE, and other studies, are finding that chronic stress is a risk factor for stroke, but it doesn’t seem to be a strong one,” says Hankey.
How stress can cause stroke
Stress is your body’s response to a perceived threat (at one time this may have been a woolly mammoth, but these days it’s more likely to be a terrible boss).
When you feel threatened your brain sends a message to your adrenal glands, which then produce hormones, including adrenalin and cortisol, that put you into ‘fight or flight’ mode and increase your breathing, heart rate and blood pressure. When stress is chronic you remain in this state of physiological arousal, which can affect many parts of your body.
There are a number of biologically plausible explanations for a link between stress and stroke, Hankey suggests. One theory suggests it might be related to high blood pressure.
“Stress could increase prolonged exposure to higher blood pressure and therefore promote damage to blood vessel walls, increase your risk of heart disease and atrial fibrillation (irregular heart beat), and it could predispose you to atheroma (swelling in an artery wall), and aneurisms (a bulge in a blood vessel wall) and ischemic stroke.”
In addition, acute stressful events – such as death of a spouse or losing your job – have been linked to heart attacks, and while there is no firm evidence that these can cause stroke, it is also biologically plausible, Hankey says.
The adrenalin you produce when you experience stress can affect the platelets in your blood and promote clotting, possibly causing a blockage of arteries in or near the brain.
“Platelets can get activated by adrenalin and so if you are in a stressful situation and therefore secreting lots of adrenalin that can activate platelets and promote clotting. So there is some sort of biological rationale that suggests perhaps in acute stressful situations you could be at risk of stroke.”
Dr Craig Hassed, a senior lecturer in general practice at Monash University who’s studied stress extensively, agrees.
While stress can be difficult to define, there are many studies showing a link between significant ongoing stress and increased risk of high blood pressure and cardiovascular events, says Hassed. “The evidence I think is probably stronger for heart disease but I think there’s enough evidence to say it’s important for stroke as well.”
When studies look for associations between so-called “stressful events” and a later stroke, they may underestimate the true risk because people’s responses to events like divorce or changing jobs, vary enormously, he says. “For one person, it’s a relief, for another it’s very traumatic.”
Looking for associations between a report of a genuine experience of stress and a later stroke is more reliable, he says.
Type A personalities
An interesting aspect of the Spanish study was that people who exhibited ‘Type A’ behaviours – such as aggressiveness and competitiveness – had double the risk of stroke compared with those who were more laid-back.
Again the link between Type As and stroke is not clear, but the association found in the study between these traits and risk of stroke was quite strong, Anderson says.
“We see these people all the time, they are managers, project leaders, business people. They are a very driven type of person compared with the more relaxed public servant,” he says.
For these people, changing how they deal with stressful life events is important, says Anderson.
“Life events happen, we can’t modify that, but what can modify is the manner in which we cope with it. Your personality is what it is and you can’t really change that, but to a certain extent you can change your behaviour and how you cope with stress,” he says.
The effects of stress
It’s also worth considering that the ways in which some of us deal with stress can increase your risk for stroke.
For example, some people use cigarettes and alcohol to help them manage stress. But both of these can increase your chances of having a stroke and can contribute to high blood pressure.
“People who smoke and get under stress smoke more cigarettes. [Some will] drink more to combat the stress and to help them sleep, but you don’t sleep very well. So all of these things can affect your physiology and put yourself at risk of both heart problems and stroke,” he says.
Also people tend to forget to take their medications – such as blood pressure medication – when they are stressed, Anderson says.
Reducing your risk of stroke
Interestingly, when it comes to making lifestyle changes to reduce your risk of stroke, some of these can also help reduce your level of stress. These include:
- not smoking
- limiting your alcohol intake (no more than 2 drinks per day)
- visiting your GP at least once a year for blood pressure and cholesterol checks (this is for men over 40 and women over 50)
- maintaining a healthy weight
- eating a balanced diet
- exercising regularly.
Even if we don’t fully understand the links between stroke and stress, there are still plenty of other reasons to learn to manage your stress better. Check out our articles.