Table 2.
Annual Average Summary Characteristics for Selected ZIP Codes Included in the Analysis (2000-2012)
| Variable | Median (Interquartile Range) |
|---|---|
| Medicare enrollees | 236 (72, 938) |
| Health outcome | |
| ARDS | 1 (0, 3); maximum 93 |
| ARDS with sepsis | 0 (0, 1); maximum 73 |
| ARDS with pneumonia | 0 (0, 0); maximum 31 |
| ARDS with traumatic injury | 0 (0, 0); maximum 12 |
| Air pollutants | |
| PM2.5′ µg/m3 | 10.8 (9.1, 12.9) |
| Ozone, ppb | 39.1 (36.7, 41.6) |
| Meteorological variables | |
| Air temperature, K | 286.3 (283.5, 290.4) |
| Dew point, K | 280.2 (277.8, 283.1) |
| Demographic information | |
| Race | |
| White | 0.97 (0.87, 0.99) |
| Black | 0.01 (0.00, 0.05) |
| Asian | 0 (0, 0) |
| Hispanic | 0 (0, 0) |
| Native American | 0 (0, 0) |
| Other | 0.55 (0.51, 0.59) |
| Female | 0.12 (0.09, 0.15) |
| Older adults aged ≥ 85 y | |
| ZIP code level SES | |
| Median household income, $ | 42,150 (33,990, 54,060) |
| Ever smoking | 0.44 (0.42, 0.50) |
Inclusion criteria are described in Figure 1. All variables in demographic information mean the proportion of different racial groups, the proportion of female subjects, and the proportion of older adults aged ≥ 85 years among Medicare enrollees in each ZIP code. Ever smoking means the proportion of ever smokers in each ZIP code obtained from the Behavioral Risk Factor Surveillance System. Median household income was rounded to the nearest 10 for simplification. PM2.5 = particulate matter with an aerodynamic diameter < 2.5 μm; ppb = parts per billion; SES = socioeconomic status.