title: Using structured additive regression models to estimate risk factors of malaria: analysis of 2010 Malawi malaria indicator survey data.
abstract: BACKGROUND
  After years of implementing Roll Back Malaria (RBM) interventions, the changing landscape of malaria in terms of risk factors and spatial pattern has not been fully investigated. This paper uses the 2010 malaria indicator survey data to investigate if known malaria risk factors remain relevant after many years of interventions.
  
  
  METHODS
  We adopted a structured additive logistic regression model that allowed for spatial correlation, to more realistically estimate malaria risk factors. Our model included child and household level covariates, as well as climatic and environmental factors. Continuous variables were modelled by assuming second order random walk priors, while spatial correlation was specified as a Markov random field prior, with fixed effects assigned diffuse priors. Inference was fully Bayesian resulting in an under five malaria risk map for Malawi.
  
  
  RESULTS
  Malaria risk increased with increasing age of the child. With respect to socio-economic factors, the greater the household wealth, the lower the malaria prevalence. A general decline in malaria risk was observed as altitude increased. Minimum temperatures and average total rainfall in the three months preceding the survey did not show a strong association with disease risk.
  
  
  CONCLUSIONS
  The structured additive regression model offered a flexible extension to standard regression models by enabling simultaneous modelling of possible nonlinear effects of continuous covariates, spatial correlation and heterogeneity, while estimating usual fixed effects of categorical and continuous observed variables. Our results confirmed that malaria epidemiology is a complex interaction of biotic and abiotic factors, both at the individual, household and community level and that risk factors are still relevant many years after extensive implementation of RBM activities.
authors.affiliation: Chancellor College, University of Malawi, Zomba, Malawi; UNC Project, Lilongwe, Malawi.
authors.forename: James
authors.initials: J
authors.lastname: Chirombo
authors.affiliation: Institut Català de Ciències del Clima (IC3), Barcelona, Spain; Abdus Salam International Centre for Theoretical Physics, Trieste, Italy.
authors.forename: Rachel
authors.initials: R
authors.lastname: Lowe
authors.affiliation: Department of Statistics and Population Studies, University of Namibia, Windhoek, Namibia.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Kazembe
mesh_terms: D001499:Bayes Theorem; D002675:Child, Preschool; D002980:Climate; D003625:Data Collection; D004777:Environment; D005260:Female; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008288:Malaria / Q000453:epidemiology*; D008295:Malawi / Q000453:epidemiology; D008297:Male; D015233:Models, Statistical; D012307:Risk Factors; D012959:Socioeconomic Factors