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Table 1 The association between brucellosis incidence and influencing factors by Poisson regression

From: Epidemiological features and risk factors associated with the spatial and temporal distribution of human brucellosis in China

Variables (unit) (a) Average yearly incidence (95% CI, per 100,000 person-years) Univariate analysis Multivariate analysis
Crude IRR (95% CI) P-value Adjusted IRR(b)(95% CI) P-value
Sheep (categorical, 1000 heads)      
< 0.03 0.23 (0.03 - 0.43)     
0.03 - 1.00 (0.63 - 1.36)     
> 8 14.30 (9.76 - 18.84)     
Sheep (continuous, 100,000 heads)   1.54 (1.48 - 1.60) < 0.001 1.42 (1.28 - 1.57) < 0.001
Goats (categorical, 1000 heads)      
< 0.3 0.95 (0.63 - 1.27)     
0.3 - 3.56 (2.38 - 4.74)     
> 3 10.10 (5.87 - 14.33)     
Goats (continuous, 100,000 heads)   1.41 (1.22 - 1.62) < 0.001 1.15 (1.01 - 1.32) 0.033
Swine (categorical, 1000 heads)      
< 30 7.79 (3.91 - 11.67)     
30 - 4.28 (2.96 - 5.59)     
> 150 1.95 (1.11 - 2.78)     
Swine (continuous, 100,000 heads)   0.64 (0.48 - 0.87) 0.004 0.80 (0.66 - 0.96) 0.016
Cattle (categorical, 1000 heads)      
< 3 1.23 (0.77 - 1.70)     
3 - 4.82 (2.86 - 6.78)     
> 30 8.49 (4.43 - 12.56)     
Cattle (continuous, 100,000 heads)   1.44 (0.95 - 2.19) 0.084 0.70 (0.44 - 1.11) 0.126
Elevation (categorical, 1000 m)      
< 0.4 1.59 (0.90 - 2.28) 1 - 1 -
0.4 - 4.17 (2.17 - 6.18) 2.97 (1.44 - 6.16) 0.003 3.31 (1.93 - 5.68) < 0.001
0.8 - 17.47 (10.25 - 24.68) 10.12 (5.78 - 17.72) < 0.001 5.77 (3.68 - 9.05) < 0.001
> 1.6 0.78 (0.07 - 1.49) 0.70 (0.12 - 4.23) 0.701 0.44 (0.12 - 1.69) 0.234
Croplands (categorical,%)§      
< 20 7.26 (3.29 - 11.23)     
20 - 3.97 (2.97 - 4.96 )     
> 50 3.05 (1.85 - 4.25 )     
Croplands (continuous, 10%)   1.00 (0.99 - 1.00) 0.758   
Forests (categorical,%)§      
< 5 7.75 (3.70 - 11.81)     
5 - 5.46 (3.98 - 6.93)     
> 40 1.25 (0.75 - 1.76 )     
Forests (continuous, 10%)   1.00 (0.99 - 1.00) 0.976   
Grassland (categorical,%)§      
< 2 0.28 (0.20 - 0.37 )     
2 - 2.09 (1.50 - 2.68 )     
> 20 13.33 (8.66 - 18.01 )     
Grassland (continuous, 10%)   1.03 (1.01 - 1.04) < 0.001 1.03 (1.01 - 1.04) < 0.001
  1. (a) For all continuous variables, we also report categorical results to allow inspection of the data and whether or not the assumption of continuous variables was justified.
  2. (b) Adjusted IRR was corrected for over-dispersion in multivariate analysis. § The area percentage occupied by croplands, forests or grassland, respectively.