Skip to main content

See also:

Climate change reported to increase stroke risk

Cold weather, high humidity, and abrupt climate changes increase the risk of a stroke
Cold weather, high humidity, and abrupt climate changes increase the risk of a stroke
Robin Wulffson, M.D.

Angelenos enjoy a balmy climate, low humidity, and mild temperature fluctuations—according to a new study, this type of environment reduces one’s risk of stroke. In contrast, cold weather, high humidity, and abrupt climate changes increase the risk of a stroke. The study was conducted by researchers affiliated with Harvard and Duke. They presented their findings on February 12 at the American Stroke Association International Stroke Conference in San Diego.

According to the Los Angeles County Department of Public Health, stoke is the second leading cause of death, behind coronary artery disease, in the county. Each year, approximately 800,000 Americans suffer a stroke. Most are due to a blood clot that blocks a blood vessel in the brain. This type of stroke is known as an ischemic stroke; hemorrhagic strokes are caused by a rupture of a blood vessel in the brain. High blood pressure is a major risk factor for both types of strokes. In cold weather, blood vessels constrict, which can cause blood pressure to rise. In addition, extreme weather can trigger a stress reaction, which can result in the body releasing substances such as epinephrine that can increase the load on the heart and increase clotting factors in the blood. Thus, a stress reaction increases the risk of a stroke. Previous studies have also noted a seasonal variation in the number of strokes. Several of the authors of the present study published a study earlier this year that examined stroke deaths from 1999 through 2006 among Medicare patients and found a pattern: higher rates in the winter, lower in summer and a small peak in July. Humidity often peaks around July. High humidity may cause dehydration, which also produces stress and increases the level of clotting factors in the blood.

In the present study, in addition to stroke deaths, the researchers assessed stroke hospitalizations in a large population of adults; they accessed a federal database that included all states except Idaho, North Dakota, Delaware and New Hampshire. In addition, the investigators reviewed data from the National Climatic Data Center for 2010 and 2011; this enabled them to obtain daily climate data down to the county level. The researchers only tracked ischemic strokes in their study. The study found that lower temperatures, greater daily temperature fluctuations, and higher dew points (humidity) were related to higher stroke hospitalization rates. Each five-degree increase in daily temperature fluctuation (the highest reading minus the lowest one) raised the risk of stroke hospitalization by 6%. Each five-degree rise in the dew point (humidity) raised the risk by 2%.

Take home message:
Seniors are at higher risk of a stroke; thus, seniors should take extra precautions during stressful weather conditions; in addition, these same precautions should be observed during normal weather conditions. These include a healthy diet, curbing sodium intake, and keeping well hydrated. During hot summer days, make use of air conditioning, and keep warm in the winter.