New research presented at the American Stroke Association's recent International Stroke Conference suggests that the rates of hospitalization and death from stroke correspond to the rise and fall of environmental temperature and dew point.
Stoke is the fourth highest cause of death in the US, causing about 1 in every 18 deaths. According to the American Stroke Association, about $73.7 billion is spent on stroke-related medical costs in the US each year.
"Weather is not something people would typically associate with stroke risk," admits study author Judith H. Lichtman, PhD, MPH, "however, we've found weather conditions are among the multiple factors that are associated with stroke hospitalizations."
Lichtman and her team analyzed the medical records of 134,510 patients hospitalized in 2009-10 with ischemic stroke, which is caused by a blood clot blocking the blood flow to the brain.
They then cross-referenced this data with meteorological records of temperature and dew point data from this period.
Daily fluctuations in temperature and increased humidity may be stressors that increase stroke hospitalizations.
The team found that large daily temperature changes and higher-than-average air moisture were linked to higher hospitalization rates from stroke. Lower-than-average annual temperatures were also associated with death and hospitalization from stroke.
For each 1°F increase in average temperature, the researchers noticed an associated 0.86% decrease in the odds of stroke hospitalization and a 1.1% decrease in the odds of dying in the hospital following a stroke.
They also found that although increases in daily temperature fluctuation and average dew point were associated with increased odds of hospitalization, there was no increased risk of death.
"This study suggests that meteorological factors such as daily fluctuations in temperature and increased humidity may be stressors that increase stroke hospitalizations," Lichtman says.
"People at risk for 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."
Lichtman acknowledges that "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."
We cannot change the weather, but what can be done to lower stroke risk?
Although there are some factors that put people at risk for having a stroke that they cannot change, there are some risk factors that can be controlled.
Having a history of stroke in the family, being female, being over the age of 55 or being black all increase risk of stroke and these factors cannot be changed.
But high blood pressure, high cholesterol, diabetes, diseases of the arteries and problems with the heart are all risk factors for stroke that can be treated. Eating a healthy diet, giving up smoking and getting regular exercise are also important lifestyle behaviors for lowering stroke risk.