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?
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. Stress and stroke are often linked together anecdotally, but studying this connection is notoriously difficult. Conducting randomised controlled trials 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.
In a recent study (1), 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.
In the Interstroke Study (2), 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:
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.
Stress is your body's response to a perceived threat. 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.
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. 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. For these people, changing how they deal with stressful life events is important.
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. Also people tend to forget to take their medications - such as blood pressure medication - when they are stressed.
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:
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