This story appears in the May 2014 issue of National Geographic magazine.
The old saying “cold hands, warm heart” may have some truth to it. University of Utah researchers found that though women’s core body temperature can run 0.4°F higher than men’s, women’s hands run 2.8°F colder—87.2°F on average, compared with 90°F for men.
Blood vessels in the body’s extremities are the first to constrict when temperatures drop. The gender differences in such cold responses are still not completely understood, says Johns Hopkins University’s Fredrick Wigley, but hormone levels and muscle mass could play a role. Women are also up to five times as likely to have Raynaud’s, a disorder in which cold temperatures or even emotional stress can make blood vessels temporarily collapse. Fingers can turn white, blue, or red in even mildly cold situations, such as when opening a refrigerator. —Eve Conant