Malnutrition and mortality
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The fourth perspective with which to assess the nutritional situation in populations is the relationship between malnutrition and mortality. Malnutrition and mortality are usually closely linked. Acute protein-energy malnutrition mainly leads to death by increasing the susceptibility of malnourished individuals to infectious diseases and, once infected, increasing the severity and duration of these diseases. Thus, if the organisms which cause important infectious diseases (diarrhoea, pneumonia, malaria, measles, etc.) are not present, malnutrition may not produce as many deaths compared to a situation in which individuals are commonly exposed to these organisms.
The following figure shows possible relationships between malnutrition and mortality. In the lower left box is a population in which mortality rates and the prevalence of malnutrition are "normal." The upper left box shows the situation where, in the face of health crisis, such as an outbreak of measles or dysentery, but without food insecurity, the mortality may rise without an accompanying rise in the prevalence of malnutrition, at least in the short-term. This situation may also occur if a substantial portion of the elevated mortality is due to violence. If a food crisis alone affects the population, without a rise in the incidence of infectious diseases, the prevalence of malnutrition may elevated, but the mortality rate may not increase. This is shown in the lower right box. In many humanitarian emergencies, because of the combination of high incidence of infectious diseases, food insecurity, and a breakdown of caring practices, both malnutrition and mortality are increased.
In humanitarian emergencies involving population displacement, acute protein-energy malnutrition often contributes to extraordinarily high mortality rates. In such situations, the mechanisms of food procurement and distribution often break down at the same time as basic public health and clinical treatment measures are eroded. As a result, exposure to disease-causing organisms is more common and treatment for disease becomes less available. This greatly increases the mortality resulting from acute protein-energy malnutrition. The level of malnutrition and the rate of mortality are often linked. Below is a graph showing the mortality rates in populations with different levels of acute malnutrition. Clearly, the higher the level of malnutrition, the higher the mortality rate.
One fallacy often cited in survey reports is that high mortality, by killing off malnourished children, results in a low apparent prevalence of acute protein-energy malnutrition even in the face of food insecurity and other factors which should produce malnutrition. This has never been seen in a humanitarian emergency. If the mortality rate climbs rapidly, the prevalence of malnutrition may plateau because the rate of death from malnutrition may equal the rate at which children become newly malnourished. As seen above, some situations may have high mortality and low malnutrition, but this is because malnutrition is not a public health problem in that population, NOT because a severe malnutrition problem has been masked by high mortality.