Being able to manage levels of stress can cut the risk of stroke, the Daily Mail reported. People who have a “good sense of coherence”, a measure of “how well a person adapts to stressful situations”, are less likely to suffer a stroke. Those with a relaxed approach to problems have a 24% lower risk of stroke, the newspaper reported. BBC News quoted the lead researcher as saying: "This evidence raises the possibility that improving our ability to respond to stress may have benefits for vascular health.”
The research was based on data from a large study originally set up to look at diet and cancer, and offers some evidence of a link between an individual’s ability to adapt to an adverse event and the risk of stroke. It is not clear how this outcome relates to stress as we more commonly understand it, and the news reports may have overstated a link between ‘stress’ and stroke. More robust studies that take into account all possible reasons why people might be at greater risk of stroke are needed before the effects of stress on stroke risk are known.
Where did the story come from?
Paul Surtees and colleagues from the Cambridge Department of Public Health and Primary Care conducted this particular review of results from a large study – the EPIC-Norfolk study. It was published in the medical journal, Stroke .
What kind of scientific study was this?
The researchers undertook a secondary analysis of data from a large cohort study (the EPIC-Norfolk study) originally set up to examine a link between diet and cancer in over 20,000 people in the UK aged between 41 and 80 years old.
People were recruited to the EPIC-Norfolk study between 1993 and 1997 and information on their medical history was collected. Participants also completed a questionnaire at the start of the study – the Health and Life Experiences Questionnaire – that included three questions to measure “sense of coherence”. Sense of coherence is considered to be a marker of how well an individual is able to adapt to an adverse life event.
On average, participants were followed up for seven years and at the end of the study the researchers looked at the characteristics of people who experienced a fatal or non-fatal stroke. Using statistical methods, they assessed whether the score on the sense of coherence scale was linked to an increase in risk of strokes. In this analysis (which included about 17,000 of the original participants), they took into account some other factors that might be linked to increased stroke risk, including age, blood pressure, smoking and obesity.
What were the results of the study?
The researchers report that after taking into account the factors that may account for an increased risk of stroke, people with a strong sense of coherence were 26% less likely to have a fatal or non-fatal stroke compared with people who had a weak sense of coherence.
What interpretations did the researchers draw from these results?
The researchers conclude that “stress adaptive capacity is a potentially important candidate risk factor for stroke”.
What does the NHS Knowledge Service make of this study?
This is a large cohort study involving more than 20,000 people. The reassessment of the data to answer a different question from the original purpose of the study means that it could be considered a retrospective cohort study. These studies have particular problems, some of which affect what we can interpret from the findings of this report. The authors themselves acknowledge some of these limitations:
- There may be other conditions associated with an increased risk of stroke that have not been taken into account.
- No assumptions can be made at this stage that, as suggested by one news report, encouraging doctors to refer those considered “at risk” to self-help groups could be beneficial.
- Drawing definitive conclusions from the use of a measure of sense of coherence requires caution for two main reasons. First, the researchers do not set out to explicitly examine a link between stress and stroke. The focus of the news reports on this may be slightly misleading. There is no information available on whether sense of coherence is in any way linked to stress as we more commonly understand it. Second, the participants in the study answered only three questions to arrive at their sense of coherence score. More often, this outcome is measured using a questionnaire with 29 questions. The shortened version has had some preliminary testing, but there is no information available here whether it is as good as the longer version
Overall, although the study shows a link between a certain characteristic – sense of coherence – and risk of stroke, this is not a simple enough result to conclude that higher stress levels mean greater risk of stroke. Even the link between this outcome and risk of stroke is complex, and the absence information on all other factors that may cause an increased risk of stroke make this relationship difficult to understand.