Comorbidity in childhood in northern Ghana: magnitude, associated factors, and impact on mortality.

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.