Demographic models for child survival and implications for health intervention programmes

The child survival strategy in developing countries has beendriven largely by a selective disease control approach, whichfocuses on a few specific and inexpensive technical interventionsdirected toward conditions such as acute dehydrating diarrhoeaand the immunizable diseases. Conceptually, this approach ofdesigning health programmes in poorer developing countries byconsidering diseases one at a time is inadequate, because itfails to take into account the fact that children are typicallyafflicted with multiple disease conditions concurrently as wellas sequentially. Furthermore, this technology-centred approachautomatically eliminates from consideration a range of interventionsfor highly prevalent conditions such as low birth weight, parasiticinfestations, or vitamin A deficiency, which may not be consideredas direct ‘causes’ of death but, in fact, have amajor indirect contribution to mortality by making childrenmore frail. In this paper we develop an analytical model which demonstrateshow multiple disease conditions interact through the mechanismsof competing risks and production of frailty to produce thehigh mortality levels witnessed among children in developingcountries. This model permits an assessment of the demographicimpact of different combinations of disease control interventionson reducing infant mortality. In terms of health policy, theanalytical model demonstrates that there are multiple routesto improving child survival in developing country populations.Important in this context is the evidence that a modest reductionin several risk factors simultaneously - for example by improvinghousehold sanitation and personal hygiene - has the potentialfor producing substantial improvements in infant and child survival.The model does confirm a role for selective primary health care,but the criteria for selecting diseases for intervention shouldrelate not only to their anticipated direct impacts on mortality,but also to their indirect effects on mortality through leavinglarge numbers of afflicted survivors more frail, and thereforeat greater risk of dying of other disease conditions.