Table 3:
Poisson fixed effects regression model
| Population | Percent change in monthly mortality rate associated with 1 additional extreme heat day per month (95% CI)* | p-value | Deaths per 10 million individuals per month associated with 1 extreme heat day per month (95% CI)*† | Estimated total number of deaths associated with extreme heat days from 2008 to 2017 (95% CI)†‡ |
|---|---|---|---|---|
| Outcome: Cardiovascular mortality: | ||||
| All adults | 0.13 (0.04 to 0.21) | 0.004 | 3.14 (1.04 to 5.25) | 5,958.1 (1847.4 to 10,068.8) |
| Non-elderly adults (20 to 64 years old) | 0.20 (0.07 to 0.33) | 0.003 | 1.28 (0.41 to 2.16) | 1,749.0 (558.3 to 2,939.7) |
| Elderly adults (65 years and older) | 0.12 (0.02 to 0.21) | 0.02 | 13.08 (2.87 to 23.29) | 4,834.0 (900.6 to 8,767.5) |
| Female | 0.021 (−0.07 to 0.11) | 0.64 | 0.45 (−1.45 to 2.34) | 429.8 (−1,388.5 to 2,248.1) |
| Male | 0.22 (0.10 to 0.34) | <0.001 | 6.56 (3.03 to 10.08) | 6,083.4 (2,748.0 to 9,418.7) |
| Non-Hispanic Black | 0.29 (0.12 to 0.46) | 0.001 | 10.10 (4.07 to 16.14) | 2,582.4 (1,053.0 to 4,111.9) |
| Non-Hispanic White | 0.10 (0.005 to 0.19) | 0.04 | 2.45 (0.13 to 4.77) | 3,090.5 (125.5 to 6,055.5) |
| Non-Hispanic other race | 0.41 (−0.07 to 0.89) | 0.09 | 5.82 (−1.30 to 12.95) | 647.5 (−145.4 to 1,440.5) |
| Hispanic (any race) | 0.07 (−0.14 to 0.27) | 0.54 | 0.84 (−1.84 to 3.52) | 319.4 (−705.4 to 1,344.3) |
| County metropolitan status (all adults) § ‖ | ||||
| Metropolitan | 0.15 (0.06 to 0.24) | 0.001 | 3.64 (1.48 to 5.80) | 5,856.9 (2,250.7 to 9,463.1) |
| Non-metropolitan | 0.05 (−0.06 to 0.17) | 0.35 | 1.54 (−1.68 to 4.77) | 451.8 (−495.5 to 1,399.2) |
| Regions (all adults) | ||||
| Midwest | 0.12 (0.003 to 0.24) | 0.04 | 3.13 (0.09 to 6.16) | 1,302.1 (33.0 to 2,571.2) |
| Northeast | 0.18 (−0.03 to 0.40) | 0.10 | 4.47 (−0.82 to 9.76) | 1,121.2 (−212.7 to 2,455.1) |
| South | 0.12 (0.05 to 0.18) | <0.001 | 2.94 (1.32 to 4.56) | 3,094.7 (1,377.4 to 4,812.1) |
| West | 0.36 (0.17 to 0.55) | <0.001 | 8.36 (3.86 to 12.86) | 1,644.3 (766.8 to 2,521.9) |
| Tertiles of total extreme heat days (all adults) ‖ # | ||||
| First tertile | 0.34 (0.22 to 0.47) | <0.001 | 7.99 (5.02 to 10.97) | 3,791.4 (2,360.5 to 5,222.3) |
| Second tertile | 0.14 (0.04 to 0.25) | 0.01 | 3.48 (1.02 to 5.94) | 2,313.5 (673.3 to 3,953.8) |
| Third tertile | 0.09 (0.13 to 0.16) | 0.02 | 2.39 (0.36 to 4.42) | 1,784.2 (264.0 to 3,304.4) |
| Alternate extreme heat definitions (all adults) | ||||
| 95th percentile | 0.09 (0.03 to 0.14) | 0.002 | 2.15 (0.79 to 3.52) | 7,144.4 (4,015.9 to 10,272.9) |
| 90th percentile | 0.07 (0.02 to 0.11) | 0.01 | 1.61 (0.47 to 2.75) | 7,184.1 (3,604.6 to 10,763.6) |
| Occurrence of a heat wave during a month** | 0.16 (0.07 to 0.26) | 0.001 | 4.10 (1.83 to 6.37) | 2,407.8 (998.9 to 3,816.6) |
| Outcome: Ischemic heart disease mortality | ||||
| All adults | 0.19 (0.07 to 0.31) | 0.002 | 2.27 (0.85 to 3.69) | 4,156.1 (1,458.4 to 6,853.7) |
| Outcome: Stroke mortality | ||||
| All adults | 0.04 (−0.12 to 0.20) | 0.60 | 0.15 (−0.37 to 0.66) | 367.4 (−1,031.1 to 1,766.0) |
Extreme heat day designated if maximum heat index on that day was ≥90°F (32.2°C) and in the 99th percentile of the maximum heat index in the baseline period (1979 to 2007).
Confidence interval crossing 0 indicates estimate for number of deaths not statistically significantly different from 0.
Estimates based on fixed effects regression coefficients, annual adult population, monthly number of extreme heat days, and value of each covariate in each county from 2008 to 2017.
County metropolitan status based on the 2013 National Center for Health Statistics Urban-Rural Classification Scheme
State-level clustered standard errors not used due to the small number of states in each stratum
Tertiles of US counties by total number of extreme heat days in summer months (May to September) from 2008 to 2017. 1st tertile : 0 to 74 days, 2nd tertile 75 to 108 days, 3rd tertile: 109 to 198 days.
Heat wave defined as three or more consecutive days of extreme heat in a month