Variable a)
| IRR b)
| 95% CI c)
| P-value d)
|
---|
Year | 2007 | Reference | - | - |
| 2008 | 1.17 | 1.05-1.31 | 0.005 |
| 2009 | 1.18 | 1.06-1.32 | 0.003 |
Season | Fall | Reference | - | - |
| Spring | 1.14 | 1.01-1.29 | 0.040 |
| Summer | 1.06 | 0.93-1.20 | 0.377 |
| Winter | 1.06 | 0.93-1.20 | 0.413 |
Age (years) | 0-4 | Reference | - | - |
| 5-9 | 0.64 | 0.52-0.78 | < 0.001 |
| 10-19 | 0.44 | 0.34-0.51 | < 0.001 |
| 20-29 | 0.51 | 0.43-0.60 | < 0.001 |
| 30-39 | 0.34 | 0.28-0.40 | < 0.001 |
| 40-49 | 0.31 | 0.26-0.37 | < 0.001 |
| 50-59 | 0.33 | 0.28-0.40 | < 0.001 |
| ≥ 60 | 0.31 | 0.26-0.37 | < 0.001 |
Sex | Female | Reference | - | - |
| Male | 0.95 | 0.87-1.04 | 0.273 |
Intercept | 0.00002 | 0.00002-0.00003 | < 0.001 |
-
a) Multi-level mixed-effects Poisson regression model using adaptive Gaussian quadrature. Public health unit (PHU) was included as a random intercept. Variance of PHU random effects = 0.074 [95% CI = 0.036-0.153]. Dependent variable: number of Salmonella Enteritidis cases by year, season, age group, sex, and PHU. Offset: natural log-transformed year-, age group-, sex-, and PHU-based population size estimates. b) IRR: Incidence rate ratio for categorical independent variables, in which the incidence rate (IR) in the category of interest was compared to the IR in the reference category. c) CI: Confidence interval of the IRR. d) Statistically significant at P ≤ 0.05.