title: Comorbidity in childhood in northern Ghana: magnitude, associated factors, and impact on mortality.
abstract: BACKGROUND
  It has been observed that in developing countries terminal illness in children under 5 yr of age is frequently characterized by comorbidity. This study seeks to quantify the co-occurrence of illness at the community level and investigates whether this co-occurrence increases the risk of mortality. We develop an appropriate measure of co-occurrence and investigate whether the comorbidity occurs by chance or whether it is due to shared risk factors.
  
  
  METHODS
  The data used for the analysis was taken from a study carried out from 1989 to 1991 in northern Ghana on children aged 2-59 months (n = 1879). Coding for diarrhoea, pneumonia, and measles was carried out using the classification system of the WHO/UNICEF strategy for the Integrated Management of Childhood Illness; malaria was confirmed by laboratory analysis. A bivariate probit analysis was conducted to quantify comorbidity. We used an additive regression model, implemented using the Generalized Estimating Equation approach, to examine the impact on mortality.
  
  
  RESULTS
  There is evidence of co-occurrence of diarrhoeal diseases and pneumonia, with greater comorbidity with increasing severity of disease. There is no evidence that the co-occurrence of diarrhoea with severe dehydration and severe pneumonia is characterized by a synergistic effect on mortality risk.
  
  
  CONCLUSIONS
  Our study has shown that it is possible to have significant co-occurrence of illness at the community level. The bivariate probit procedure was easily adopted and considered appropriate for the analysis of comorbidity. The lack of suitable datasets for a more thorough analysis of comorbidity, and for the evaluation of synergistic effects on mortality, is a major limitation.
authors.affiliation: Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK. bridget.fenn@lshtm.ac.uk
authors.forename: Bridget
authors.initials: B
authors.lastname: Fenn
authors.forename: Saul S
authors.initials: SS
authors.lastname: Morris
authors.forename: Robert E
authors.initials: RE
authors.lastname: Black
mesh_terms: D002675:Child, Preschool; D003153:Community Health Services; D015897:Comorbidity; D003906:Developing Countries; D003967:Diarrhea / Q000453:epidemiology* / Q000401:mortality; D005260:Female; D005869:Ghana / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007226:Infant Mortality; D007231:Infant, Newborn; D008288:Malaria / Q000453:epidemiology* / Q000401:mortality; D008297:Male; D008457:Measles / Q000453:epidemiology* / Q000401:mortality; D011014:Pneumonia / Q000453:epidemiology* / Q000401:mortality; D012044:Regression Analysis