A-Z Guide to the Year in Medicine

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LAUGHTER Remember the last time you laughed so hard you couldn't stop? Good. Do it again. Laughter increases blood flow by causing the inner lining of blood vessels (the endothelium) to expand, according to a small study of healthy moviegoers who were shown both funny and distressing clips from films and then tested for the physical effects of each. With laughter, blood flow increased 22%; under stress, it decreased 35%.

LONGEVITY Why do some people live longer than others? One clue comes from a 15-year study of three Greek villages with a combined population of about 1,100. Although those who lived more than 3,000 ft. above sea level had more cardiovascular risk factors--such as higher blood pressure and blood-fat levels--they had lower death rates and fewer deaths from heart disease than their lowland counterparts. Researchers theorize that mountain dwellers may be strengthened by a lifetime of arduous hiking and better adapted physiologically to cope over the long term with high-altitude oxygen levels and other cardiovascular stresses.