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Table 3 Predictors of malaria incidence in a fixed cohort of 1,199 children age six to 59 months at baseline, Liwonde, Malawi 2012- 2013 a

From: A cohort study of the effectiveness of insecticide-treated bed nets to prevent malaria in an area of moderate pyrethroid resistance, Malawi

     Univariate Multivariate
Characteristic   Malaria infections (n) Person-years at risk Observed incidence PPY Rate ratio (95% CI) P value Adjusted incidence b PPY (95% CI) Rate ratio (95% CI) P value
Age (months) 6-11 64 17 3.7 (2.7-5.0) 2.2 (1.6-3.0) <0.0001 2.1 (1.5-2.9) 1.0 (0.8-1.4) 0.84
  12+ 1845 891 1.7 (1.6-1.8) 1.0   2.0 (1.8-2.3) 1.0  
Sex Female 905 433 1.7 (1.6-1.9) 1.0 (0.9-1.1) 0.96    
  Male 1004 471 1.7 (1.6-1.9) 1.0     
Baseline Plasmodium infection Positive 948 329 2.4 (2.2-2.7) 1.7 (1.5-2.0) <0.0001 2.7 (2.2-3.3) 1.7 (1.5-1.9) <0.0001
Negative 960 573 1.4 (1.3-1.5) 1.0   1.6 (1.3-2.0) 1.0  
Bed net use ITN 1710 864 1.6 (1.5-1.7) 0.4 (0.3-0.5) <0.0001 1.7 (1.5-2.1) 0.7 (0.5-0.8) <0.0001
  UTN 92 17 4.9 (4.1-5.9) 1.1 (0.8-1.5) 0.53 2.0 (1.6-2.6) 0.8 (0.6-1.0) 0.06
  No bed net 86 15 4.4 (3.5-5.7) 1.0   2.6 (2.0-3.3) 1.0  
Wealth index Poorest 725 290 2.1 (1.9-2.3) 1.5 (1.3-1.8) <0.0001 2.3 (1.9-2.8) 1.3 (1.1-1.5) 0.0008
  Middle 647 296 1.8 (1.6-2.0) 1.3 (1.1-1.6) 0.001 2.2 (1.8-2.7) 1.2 (1.1-1.5) 0.01
  Least poor 495 309 1.4 (1.2-1.6) 1.0   1.8 (1.4-2.2) 1.0  
Caregiver completed primary Yes 239 164 1.2 (0.9-1.4) 0.6 (0.5-0.8) <0.0001 1.9 (1.5-2.4) 0.8 (0.7-1.0) 0.02
No 1628 730 1.9 (1.7-2.0) 1.0   2.3 (1.9-2.8) 1.0  
Altitude Lowest 680 300 1.9 (1.7-2.1) 1.4 (1.2-1.7) 0.0001 2.4 (1.9-2.9) 1.5 (1.3-1.8) <0.0001
  Middle 727 294 2.1 (1.9-2.4) 1.6 (1.3-1.9) <0.0001 2.4 (2.0-2.9) 1.5 (1.3-1.8) <0.0001
  Highest 497 307 1.3 (1.2-1.5) 1.0   1. (1.3-2.0) 1.0  
Number of ITNs <300 m Lowest 586 249 2.0 (1.8-2.3) 1.7 (1.4-2.1) <0.0001 2.1 (1.7-2.6) 1.1 (0.9-1.4) 0.39
Middle 737 313 2.1 (1.9-2.3) 1.7 (1.5-2.1) <0.0001 2.2 (1.8-2.7) 1.2 (0.9-1.4) 0.17
  Highest 389 272 1.2 (1.0-1.4) 1.0   1.9 (1.5-2.4) 1.0  
IDW malaria prevalence Lowest 474 294 1.3 (1.1-1.5) 0.6 (0.5-0.7) <0.0001 1.7 (1.3-2.1) 0.7 (0.5-0.8) 0.0002
Middle 610 304 1.7 (1.5-1.9) 0.8 (0.6-0.9) 0.0003 2.2 (1.7-2.7) 0.9 (0.7-1.0) 0.04
  Highest 820 302 2.3 (2.1-2.5) 1.0   2.5 (2.1-3.1) 1.0  
Season Apr-June 844 178 4.1 (3.8-4.4) 2.3 (2.0-2.7) <0.0001 4.6 (3.9-5.5) 2.3 (2.0-2.6) <0.0001
  July-Dec 556 486 0.9 (0.8-1.0) 0.5 (0.4-0.6) <0.0001 1.0 (0.8-1.2) 0.5 (0.4-0.6) <0.0001
  Jan-Mar 509 241 1.8 (1.6-2.0) 1.0   2.0 (1.6-2.5) 1.0  
  1. a PPY = per person year; IDW = inverse distance-weighted; ITN = insecticide-treated bed net; UTN = untreated bed net; CI = confidence interval.
  2. b Incidence is model-adjusted for all other variables in the column.