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Volume 21, Number 9—September 2015
THEME ISSUE
Emerging Infections Program
Emerging Infections Program

Socioeconomic Disparities and Influenza Hospitalizations, Tennessee, USA

Chantel Sloan, Rameela Chandrasekhar, Edward F. Mitchel, William Schaffner, and Mary Lou LindegrenComments to Author 
Author affiliations: Brigham Young University, Provo, Utah, USA (C. Sloan); Vanderbilt University School of Medicine, Nashville, Tennessee, USA (C. Sloan, R. Chandrasekhar, E. Mitchel, W. Schaffner, M.L. Lindegren)

Main Article

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.

Main Article

Page created: August 12, 2015
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