Mortality displacement as a function of heat event strength in 7 us cities

Michael V. Saha, Robert E. Davis, David Hondula

Research output: Contribution to journalArticlepeer-review

80 Scopus citations


Mortality rates increase immediately after periods of high air temperature. In the days and weeks after heat events, time series may exhibit mortality displacement - periods of lower than expected mortality. We examined all-cause mortality and meteorological data from 1980 to 2009 in the cities of Atlanta, Georgia; Boston, Massachusetts; Minneapolis-St. Paul, Minnesota; Philadelphia, Pennsylvania; Phoenix, Arizona; Seattle, Washington; and St. Louis, Missouri. We modeled baseline mortality using a generalized additive model. Heat waves were defined as periods of 3 or more consecutive days in which the apparent temperature exceeded a variable percentile. For each heat wave, we calculated the sum of excess and deficit mortality. Mortality displacement, which is the ratio of grand sum deficit to grand sum excess mortality, decreased as a function of event strength in all cities. Displacement was close to 1.00 for the weakest events. At the highest temperatures, displacement varied from 0.35 (95% confidence interval: 0.21, 0.55) to 0.75 (95% confidence interval: 0.54, 0.97). We found strong evidence of acclimatization across cities. Without consideration of displacement effects, the net impacts of heat-wave mortality are likely to be significant overestimations. A statistically significant positive relationship between the onset temperature of nondisplaced heat mortality and mean warm-season temperature (R2 = 0.78, P < 0.01) suggests that heat mortality thresholds may be predictable across cities.

Original languageEnglish (US)
Pages (from-to)467-474
Number of pages8
JournalAmerican journal of epidemiology
Issue number4
StatePublished - Feb 15 2014


  • United States
  • apparent temperature
  • harvesting
  • heat
  • heat waves
  • human biometeorology
  • mortality displacement
  • temperature

ASJC Scopus subject areas

  • Epidemiology


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