Season may affect blood pressure

For people with high blood pressure, the condition can prove tougher to control in the winter.

In a five-year study that focused on blood pressure readings, 443,632 U.S. military veterans with hypertension, or high blood pressure, were studied in 15 cities, including such far-flung locales as chilly Anchorage and warm San Juan, Puerto Rico. In each place, the researchers found, fewer of the veterans -- regardless or race or sex -- returned to normal blood pressure levels while treated in winter months compared with the summer.

The researchers have not figured out just what is causing this, but it did not seem to be changes in temperature or daylight that occur in the winter or the latitude of the city, said Department of Veterans Affairs researcher Dr. Ross Fletcher, chief of staff at the VA Medical Center in Washington who led the study.

Instead, Fletcher said, the trend may be driven by weight gain, different eating habits and less exercise during winter.