Table 4.
Average mortality effects of the first heat wave in a summer versus later heat waves (1987–2005).
| Region | Average percentage of heat waves that were first in season | Average effect of heat waves (95% PI) |
|
|---|---|---|---|
| First in season | Not first in season | ||
| National (n = 43) | 40% | 5.04% (3.06 to 7.06%) | 2.65% (1.14 to 4.18%) |
| Northeast (n = 7) | 40% | 11.08% (4.05 to 18.58%) | 3.45% (−1.16 to 8.28%) |
| Midwest (n = 12) | 38% | 5.29% (1.76 to 8.94%) | 5.42% (2.46 to 8.46%) |
| South (n = 19) | 38% | 3.29% (0.12 to 6.56%) | 0.68% (−1.60 to 3.02%) |
The heat wave effect is the increase in nonaccidental mortality risk for heat wave days compared with non-heat wave days, controlling for daily temperature [the added heat wave effect described by Hajat et al. (2006)].