Volume 21, Number 9—September 2015
THEME ISSUE
Emerging Infections Program
Emerging Infections Program
Socioeconomic Disparities and Influenza Hospitalizations, Tennessee, USA
Table 1
Average annual crude and age-standardized incidence rates and relative rates of influenza hospitalization by demographic and neighborhood measures, Middle Tennessee, USA, October 2007–April 2014*
| Characteristic | Hospitalizations, no. (%), N = 1,743 | Crude incidence (95% CI) | Age-standardized incidence (95% CI) | Rate ratio (95% CI) | Rate difference (95% CI) | RII† |
|---|---|---|---|---|---|---|
| Individual-level data† | ||||||
| Sex | NA | |||||
| M | 775 (44.5) | 15.1 (14.0–16.2) | 16 (14.9–17.2) | NA | NA | |
| F | 968 (55.5) | 18.0 (16.8–19.1) | 17.8 (16.7–19.0) | 1.1 (1.0–1.2) | 1.8 (0.2–3.4) | |
| Race§ | NA | |||||
| White | 1,242 (73.4) | 15.3 (14.5–16.2) | 15.2 (14.4–16.1) | NA | NA | |
| African American | 418 (24.7) | 24.7 (22.4–27.1) | 27.4 (24.8 30.3) | 1.8 (1.6–2.0) | 12.2 (9.4–15.0) | |
| Other | 31 (1.8) | 4.4 (2.8–5.9) | 4.0 (2.5–6.5) | 0.3 (0.2–0.4) | −11.2 (−13.1 to –9.3) | |
| Age, y | NA | |||||
| <5 | 207 (11.9) | 28.3 (24.4–32.2) | NA | NA | NA | |
| 5–17 | 98 (5.6) | 5.3 (4.3–6.4) | NA | NA | NA | |
| 18–49 | 470 (27.0) | 9.6 (8.7–10.4) | NA | NA | NA | |
| 50–64 | 398 (22.8) | 20.7 (18.7–22.8) | NA | NA | NA | |
| ≥65 | 570 (32.7) | 51.7 (47.4–55.9) | NA | NA | NA | |
| Neighborhood-level data‡ | ||||||
| % Below poverty | ||||||
| <5.0 | 266 (15.3) | 11.4 (10.0–12.8) | 11.5 (10.1–13.0) | NA | NA | 2.9 (2.5–3.5) |
| 5.0–9.9 | 374 (21.5) | 14.2 (12.8–15.6) | 13.9 (12.5–15.4) | 1.2 (1.1–1.4) | 2.4 (0.5–4.4) | |
| 10.0–19.9 | 475 (27.3) | 17.3 (15.7–18.8) | 16.8 (15.3–18.4) | 1.5 (1.3–1.7) | 5.3 (3.3–7.4) | |
| ≥20.0 | 628 (36) | 24.9 (22.9–26.8) | 25.7 (23.7–27.8) | 2.2 (2.0–2.5) | 14.2 (11.8–16.7) | |
| % College education | ||||||
| 15.0–24.9 | 16 (0.9) | 38.8 (19.8–57.7) | 47.3 (23.9–92.1) | NA | NA | 0.5 (0.4–0.7) |
| 25.0–39.9 | 326 (18.7) | 21.5 (19.2–23.9) | 21.4 (19.1–23.9) | 0.5 (0.1–1.7) | −25.9 (−53.7 to 1.8) | |
| ≥40.0 | 1,401 (80.4) | 16.1 (15.3–17) | 16.1 (15.2–16.9) | 0.3 (0.1–1.9) | −31.3 (−58.9 to −3.6) | |
| % Employed | ||||||
| <50.0 | 1,122 (64.4) | 19.3 (18.2–20.4) | 18.9 (17.8–20.1) | NA | NA | 0.6 (0.5–0.7) |
| 50.0–65.9 | 605 (34.7) | 14.1 (12.9–15.2) | 14.4 (13.3–15.6) | 0.8 (0.7–0.9) | −4.5 (−6.1 to −2.9) | |
| ≥66.0–74.9 | 16 (0.9) | 12.6 (6.4–18.8) | 15.8 (8.4–27.7) | 0.8 (0.5–1.4) | −3.2 (−11.9–5.5) | |
| % Female HH | ||||||
| <20.0 | 637 (36.5) | 12.7 (11.8–13.7) | 12.7 (11.7–13.7) | NA | NA | 3.2 (2.7–3.8) |
| 20.0–39.9 | 531 (30.5) | 17.2 (15.7–18.6) | 17.2 (15.7–18.7) | 1.4 (1.2–1.5) | 4.5 (2.7–6.3) | |
| 40.0–59.9 | 340 (19.5) | 23.0 (20.6–25.4) | 22.7 (20.3–25.3) | 1.8 (1.6–2.0) | 10.0 (7.4–12.6) | |
| ≥60.0 | 235 (13.5) | 34.9 (30.5–39.4) | 36.0 (31.5–41.0) | 2.8 (2.5–3.2) | 23.3 (18.6–28.1) | |
| Household crowding, persons/room) | ||||||
| <5.0 | 1,514 (86.9) | 16.5 (15.7–17.3) | 16.4 (15.5–17.2) | NA | NA | 1.9 (1.5–2.5) |
| 5.0–9.9 | 176 (10.1) | 20.0 (17.0–23.0) | 21.6 (18.4–25.1) | 1.3 (1.1–1.5) | 5.2 (1.9–8.6) | |
| ≥10.0 | 53 (3.0) | 27.5 (20.1–34.9) | 26.9 (20.0–35.6) | 1.6 (1.2–2.2) | 10.5 (3.1–17.9) | |
| Population density, persons/mi2 | ||||||
| 0–<200 | 259 (14.9) | 14.8 (13.0–16.6) | 14.0 (12.3–15.8) | NA | NA | 1.8 (1.5–2.2) |
| 200–700 | 273 (15.7) | 13.8 (12.2–15.5) | 13.7 (12.1–15.5) | 1.0 (0.8– 1.2) | −0.3 (−2.6– 2.1) | |
| ≥700 | 1,211 (69.5) | 18.6 (17.5– 19.6) | 18.7 (17.7– 19.8) | 1.3 (1.2–1.5) | 4.7 (2.7–6.8) | |
| % Medical insurance | ||||||
| 50–74.9 | 200 (11.5) | 22.5 (19.4–25.6) | 24.1 (20.8–27.8) | 0.5 (0.3–0.6) | ||
| >75.0 | 1,543 (88.5) | 16.5 (15.7–17.3) | 16.4 (15.6–17.2) | 0.7 (0.5–0.8) | −7.8 (−11.3 to −4.3) |
*HH, head of household; RII, relative indexes of inequality; NA, not applicable.
†RII is calculated as the exponent of the slope of a Poisson regression model by using incidence rate as the outcome variable and the proportion of the population in that socioeconomic group as the predictor variable. The RII can be interpreted similarly to an incidence rate ratio that compares those in the quantitatively highest category with those in the lowest categorization. For example, an RII of 2.5 would indicate a 150% increase in risk when those in the quantitatively highest category are compared with those in the lowest (such as the <49.9% category being compared with the ≥66.0–74.9 category for patients employed). A low RII (with CIs) <1 would indicate decreased risk. An RII was not calculated for variables marked NA because they do not have a readily available ordinal variable by which to compare lowest and highest socioeconomic status.
‡Sex, race, and age characteristics use individual-level data from surveillance; neighborhood-level characteristics use data from the American Community Survey.
§The number of patients with available race data was 1,691.