EAN 2025 | The association between temperature and stroke incidence, morbidity, and mortality

When it comes to stroke, we are also aware that the distribution of acute stroke depends on the season of the year and there are many studies in the literature that explored the effect of cold temperature and hot temperature on the incidence and mortality of ischemic stroke and intracerebral hemorrhage. So basically, it was shown that cold temperature is associated with increased incidence of stroke morbidity and mortality. And this was related to the increased blood pressure and increased serum cholesterol during extreme cold temperatures. However, hot temperature was associated with increased risk of mortality of ischemic stroke and decreased risk of mortality from intracerebral hemorrhage. So, as I said, some studies have shown increased incidence of ischemic stroke compared to the incidence of intracerebral hemorrhage during summer months. But some studies actually failed to show this association between the extreme weather changes and stroke incidence. And this was also shown that there was a lack of evidence in people who had high risk of cerebrovascular and cardiovascular diseases. So patients that were older that had previous CVD, patients who had hypertension or diabetes. But actually, a significant association between cold and hot temperature was shown in elderly patients with stroke. And it was shown that cold or lower temperature increased the morbidity and mortality of stroke by 10 to 50%. And on the other hand, some studies show that increase in the mean ambient temperature was associated with decreased risk of morbidity of general stroke and hemorrhagic stroke by 1 to 7%. As I said, some studies have shown positive association between, for example, one degree increase in the diurnal temperature and the risk of general stroke and ischemic stroke morbidity. However, some studies actually showed that there is reduced risk of stroke by one degree increase in diurnal temperature. But all studies agree in general that basically there is a significant association between increase in temperature and general stroke in patients who have comorbidities such as hypertension, diabetes, atrial fibrillation or hyperlipidemia. And this was actually specifically pointed out in patients who have congestive heart failure. So basically, when they are exposed to both cold, very cold and very hot temperature, then they have increased risk of general stroke. What would be the proposed mechanism here? So basically, the proposed mechanism is that vasoconstriction diverts the blood flow to the central organs, such as the brain, the heart and the kidneys, in response to cold temperature. And then this increases the systemic vascular resistance and this leads to high blood pressure. And the mean blood pressure is actually higher in colder months. And then the systemic vascular resistance is increased. And there is also ineffective cold adaptation due to the occurrence of autonomic neuropathy in hypertensive patients. And this peripheral vasoconstriction that occurs may lead to cerebral vasculature congestion and this can increase the risk of intracerebral hemorrhage. During hot temperatures also dehydration can occur and this is also associated with increased stroke risk especially in patients who are hospitalized and this can lead to increased mortality of stroke. So basically, we have to bear in mind that high and low temperatures can increase the risk of stroke, especially in elderly patients, in patients who suffer from cardiovascular comorbidities, especially patients who suffer from congestive heart failure and therefore, this higher and lower ambient temperature should be considered as an important inflation factor when we establish the clinical guidelines for preventive intervention in patients who are at high stroke risk.

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