Table 2. Linear Fixed-Effects Regression Model Outcome: County-Level, Monthly Age-Adjusted All-Cause Mortality Rate for Adults (≥20 Years).
| Population | Additional deaths per 100 000 individuals associated with 1 additional extreme heat day per montha | Annual estimated deaths associated with extreme heat days from 2008 to 2017, mean (95% CI)b | |
|---|---|---|---|
| Estimate (95% CI) | P value | ||
| Primary analysis, all adults (aged ≥20 y) | 0.07 (0.03 to 0.12) | .001 | 1373 (584 to 2163) |
| Secondary analyses | |||
| Age 20-64 y | 0.04 (0.02 to 0.06) | .001 | 562 (234 to 890) |
| Age ≥65 y | 0.23 (0.07 to 0.38) | .01 | 802 (247 to 1358) |
| Female | 0.02 (−0.02 to 0.06) | .25 | 225 (−165 to 615) |
| Male | 0.14 (0.08 to 0.20) | <.001 | 1262 (709 to 1815) |
| Hispanic (any race) | 0.08 (0.002 to 0.16) | .045 | 219 (5 to 432) |
| Non-Hispanic | |||
| Black | 0.18 (0.10 to 0.25) | <.001 | 464 (269 to 660) |
| White | 0.07 (0.01 to 0.12) | .02 | 801 (119 to 1483) |
| Other racec | 0.07 (−0.04 to 0.18) | .23 | 76 (−49 to 200) |
| Counties (all adults)d | |||
| Metropolitan | 0.09 (0.04 to 0.13) | <.001 | 1342 (640 to 2043) |
| Nonmetropolitan | 0.03 (−0.03 to 0.09) | .34 | 83 (−90 to 256) |
| Social Vulnerability Index, tertilee | |||
| First | 0.10 (0.04 to 0.16) | .001 | 449 (188 to 710) |
| Second | 0.07 (0.02 to 0.11) | .01 | 481 (152 to 809) |
| Third | 0.05 (−0.001 to 0.11) | .05 | 378 (−7 to 763) |
| Alternative extreme heat definitions | |||
| ≥90 °F (32.2 °C) and in the 95th percentile of the maximum heat index in the baseline period (all adults) | 0.06 (0.03 to 0.08) | <.001 | 1839 (991 to 2687) |
| ≥90 °F (32.2 °C) and in the 90th percentile of the maximum heat index in the baseline period (all adults) | 0.05 (0.02 to 0.07) | <.001 | 1992 (957 to 3027) |
An extreme heat day was designated if the maximum heat index on that day was greater than or equal to 90 °F (32.2 °C) and in the 99th percentile of the maximum heat index in the baseline period (1979 to 2007).
Estimates are based on annual adult population and then number of extreme heat days in each county from 2008 to 2017.
Non-Hispanic other race population consists of county-level estimates of individuals identified as non-Hispanic and American Indian and Alaska Native, Asian, Native Hawaiian and other Pacific Islander, or identifying with 2 or more races according to the US Census Bureau.
Based on the 2013 National Center for Health Statistics Urban-Rural Scheme.
Based on the 2014 Centers for Disease Control and Prevention Social Vulnerability Index (eAppendix 3 in the Supplement). Higher values indicate a greater degree of vulnerability to public health hazards.