Changes in the weather could trigger strokes, according to new research.
A study has found the number of people admitted to hospital because of strokes may rise and fall according to changes in environmental temperature and air moisture.
Such changes also affect death rates, the study found.
Researchers discovered large swings in temperature during the day triggered a rise in the number of people who suffered strokes.
Dr Judith Lichtman, associate professor in epidemiology at the Yale School of Public Health in Connecticut, in the United States, explained: “Weather is not something people would typically associate with stroke risk.
“However, we have found that weather conditions are among the multiple factors which are associated with stroke hospitalisations.”
The study looked at a sample of 134,510 people, aged 18 years and older, and admitted to hospitals in 2009-10 for ischemic stroke – caused by a blood clot that blocks blood flow in, or leading to, the brain – and examined the weather.
Researchers found larger daily temperature changes and a higher average “dew point”, indicating higher air moisture, were associated with higher rates of stroke.
Lower average annual temperatures were associated with stroke hospitalisations and death. With each degree Fahrenheit increase in average temperature, there was a 0.86 per cent fall in the odds of being taken to hospital with a stroke and a 1.1 per cent decrease in the odds of dying in hospital after a stroke.
Increases in daily temperature fluctuation and average dew points were associated with increased odds of landing in hospital with a stroke, but not with any increased likelihood of dying in the hospital.
Prof Lichtman added: “This study suggests that meteorological factors such as daily fluctuations in temperature and increased humidity may be stressors that increase stroke hospitalisations.
“People at risk of stroke may want to avoid being exposed to significant temperature changes and high dew point and, as always, be prepared to act quickly if they or someone they know experiences stroke signs and symptoms.
“Future research is needed to better understand the cause and effect of changes in weather conditions, as well as to explore potential mechanisms for this association.”
The research was presented at the American Stroke Association’s International Stroke Conference.