Heat wave claimed solitary, sick people.

As the mercury climbed last summer, Chicago's death toll rose with it. Hospitals and medical examiners were overwhelmed as their caseloads mounted. Now a study suggests that many of the 700 deaths caused by the sizzling heat wave of July 1995 could have been averted.

The work, published in the July 11 New England Journal of Medicine, found that people who lived alone had twice the risk of death during hot weather. Those who were bedridden or needed help from visiting nurses were even more vulnerable.

The researchers also found that more than half of the deceased people had lived on the top floor of their building. Unlike some earlier studies, the new work indicates that the use of electric fans had no bearing on survival. The researchers interviewed friends, relatives, and neighbors regarding 339 people who had died in the heat. They also interviewed 339 people who were close in age to and lived in the same neighborhoods as the casualties. Those most likely to survive had air-conditioning, lived in a building with an air-conditioned lobby, or had a way to get to a cooler location, the researchers found. A network of social contacts also proved critically important.

"During the summer heat wave of 1995 in Chicago, anything that facilitated social contact, even membership in a social club or owning a pet, was associated with a decreased risk of death," note Jan C. Semenza, of the Centers for Disease Control and Prevention in Atlanta, and her coworkers. Usually, people do not succumb to the heat on the first day. Therefore, most can adapt their daily routines to ride out the heat, the researchers say.