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Table 4 Unadjusted and adjusted odds ratios from bivariate and multivariate logistic regression

From: Malaria risk in young male travellers but local transmission persists: a case–control study in low transmission Namibia

Variable Numbera Unadjusted OR (95% CI) P value Adjusted OR (95% CI) P value
Case N = 98 Control N = 634
Age group (years)
 <5 9 100 1 – 1 –
 5–14 23 210 1.13 (1.00–1.28) 0.06 1.48 (0.65–3.36) 0.35
 15–29 37 150 1.22 (1.07–1.38) 0.002 2.14 (0.99–4.63) 0.05
 30–44 14 73 1.05 (0.89–1.26) 0.52 2.23 (0.87–5.72) 0.10
 45–59 8 38 1.05 (0.80–1.37) 0.74 3.03 (1.11–8.27) 0.03
 60+ 7 63 0.90 (0.77–1.05) 0.18 1.24 (0.55–2.80) 0.61
Location slept previous night
 In household 87 624 1 – 1 –
 Away from household 11 10 2.46 (1.35–4.48) 0.003 5.61 (1.97–16.02) 0.001
 Higher socioeconomic statusb 98 634 0.78 (0.62–0.98) 0.03 0.65 (0.47–0.91) 0.01
 Squared term – – 1.10 (1.00–1.19) 0.03 1.13 (1.01–1.27) 0.04
Predicted travel time to clinic
 0–4 52 392 1 – 1 –
 5–14 43 120 2.51 (1.34–4.70) 0.004 2.07 (0.86–5.01) 0.11
 15–46 3 122 0.58 (0.15–2.33) 0.44 0.05 (0.005–0.59) 0.02
More than 15 km from Angolan border 23 298 1 – 1 –
<15 km from Angolan border 75 336 4.34 (1.91–9.85) <0.0001 2.86 (1.17–6.97) 0.02
Enhanced Vegetation Index (EVI)b
 0.11–0.24 37 443 1 – 1 –
 0.25–0.34 54 145 5.32 (2.49–11.38) <0.0001 14.62 (3.73–57.27) <0.0001
 0.35–0.45 7 46 1.70 (0.43–6.71) <0.0001 2.00 (0.23–17.20) 0.53
Total rainfall in prior month (mm)
 0–19 14 207 1 – 1 –
 20–39 63 171 7.25 (3.33–15.79) <0.0001 2.79 (1.01–7.70) 0.05
 40–67 21 256 2.14 (0.87–5.31) 0.10 0.25 (0.06–0.99) 0.05
District: Engela 51 277 1 – 1 –
 Oshikukuc 21 74 1.54 (0.62–3.81) 0.94 5.06 (1.35–18.97) 0.02
 Outapi 26 283 0.50 (0.21–1.16) 0.11 1.13 (0.45–2.87) 0.79
  1. All GEE adjusted for health district (matching variable) and clustering of controls within households. Multivariate GRR adjusted for the interaction effect of gender and travel in Table 3
  2. OR odds ratio, GEE generalized estimating equations, CI confidence interval, QIC quasilikelihood under the independence model criterion, m meters, °C degrees Celsius, mm millimeters, km kilometers
  3. aNumbers restricted to non-missing data in final multivariate model; full bivariate analyses included in Table S3
  4. bSocioeconomic measure is first component of the PCA, included as a continuous measure
  5. cThe higher adjusted odds of malaria observed in Oshikuku is attributed to a lower number of controls recruited per case in this area compared to the other districts
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