Mortality during heat waves in New York City July, 1972 and August and September, 1973.

Abstract Analysis of the causes of death by day of occurrence during two heat waves in New York City in 1972 and 1973 established that there was a great increase in the numbers of deaths in each heat wave after several days of excessively warm weather and on the day which followed the hottest day. On both these days deaths from ischaemic heart disease were far and away the most prominent cause of death and the great majority of those who died were 65 years of age or older. The observation that deaths from ischaemic heart disease in New York City heavily out-numbered deaths from cerebrovascular accidents on the two days which followed the hottest day of each of these heat waves is at variance with earlier observations which indicated that deaths from cerebrovascular accidents during months when severe heat waves occurred in the United States as a whole, and in certain states particularly affected by the heat waves, were a more prominent cause of death than ischaemic heart disease. The reason is obscure. The number of homicides in July, 1972 were significantly greater than the numbers for any of the first 8 months of the year; but the increase occurred after the heat wave was over not during the heat wave. This increase was not apparent after the shorter, though warmer, period of hot weather in 1973. Scrutiny of death certificates showed that despite the large excess of deaths above expected numbers during the heat wave in 1973 heat effects were shown on only 30 death certificates during the entire summer and on each certificate this was only one of a number of multiple causes of death. If the tabulation of deaths due to organic disease were to take precedence over deaths due to environmental causes in health reports it is possible that not even these deaths would have been shown as deaths due to excessive heat. Both heat waves were less severe than others which have occurred in New York during the past century and very much less severe than heat waves in other cities in the United States during the last twenty years. If conditions comparable to those which occurred in August, 1896, were to recur today (and this is always a possibility) and the power supplies failed to keep the city's electrically powered services operating at or near to maximum capacity, there could be an environmental disaster of unprecedented proportions.