The New York City Department of Health and Mental Hygiene analyzed data for 2000-11 and found on average, 447 patients each year were treated for heat illness and released from emergency departments, 152 were hospitalized and 13 persons died from heat stroke.
Chronic diseases, mental health disorders and obesity were common comorbidities. Records with information on cooling showed none had a working air conditioner in use among those killed by the heat.
"Outreach to city residents at high risk and their caregivers should emphasize the dangers of heat and importance of protective cooling measures during hot weather," the report said. "Improving awareness of chronic health conditions that increase vulnerability to heat is also important."
Of the 154 total deaths that occurred over the 12-year period, 45 percent died as a result of two severe heat waves in 2006 and 2011. The 2006 heat wave lasted for 10 days, with maximum heat indices above 90 degrees F, three of which exceeded 100 degrees F. The 2011 heat wave lasted four days, with a peak heat index above 110 degrees F.
Older adults had the highest rates of heat illness and death, but people of all ages are at risk, especially those with underlying physical or mental health conditions and those taking medications that can impair thermoregulation -- the ability of an organism to keep its body temperature within certain boundaries.
The findings were published in the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.