Effects of the summer heat wave of 1988 on daily mortality in Allegheny County, PA.

The authors studied total mortality in Allegheny County, PA, during the summer of 1988. A heat wave occurred in July of 1988, with daily maximum temperatures near or above 90 degrees Fahrenheit on 15 consecutive days. During that period there were a total of 694 deaths from all causes in the county, compared with an expected 587 deaths (P less than .01). All 107 excess deaths were of persons ages 65 or older, with the majority (78) occurring to persons older than age 75. Daily mortality was most closely correlated with average temperature from the previous day (R = .49, P less than .01), suggesting the cumulative effects of successive high daytime and night-time temperatures on susceptible persons. Evaluation of a possible effect on mortality of high ambient ozone levels detected in early July suggested that ozone did not contribute to excess mortality during the heat wave. Comparison of the 1988 heat wave with a less intense hot spell of 1973 indicated that excess mortality was less than would have been expected in 1988. The authors speculate that increased public awareness and the wider use of air conditioning over the years may have reduced the lethality of periods of extreme summer temperatures in urban areas. Further research is needed to evaluate this hypothesis completely. Public health officials should continue to monitor weather forecasts for predictions of extended periods of unusual heat and should warn the public to take suitable precautions during such periods.