But this could be treatable. Iron deficiency has been called "the most common preventable nutritional deficiency". Interventions to reduce the health burden associated with iron deficiency, such as fortification and supplementation, have been claimed by some organizations to significantly reduce mortality and the risk of disease within a population. But are they correct?
What are the resultant health improvements following the introduction of interventions aimed to reduce iron deficiency in developing countries? Unfortunately, a quick review of the literature revealed that few studies have quantitatively measured the total health benefits from micronutrient fortification in countries where the disease has a substantial impact.
Due to the lack of directly-relevant data available, we looked to indirectly calculate the total health gain for an intervention by searching for data on four important parameters often reported within studies, albeit separately:
We first searched key repositories of health related publications including PubMed, the World Health Organisation (WHO) and Cochrane websites using a variety of combinations of disease and Disability-Adjusted Life Years (DALY)-related search terms. Disability-Adjusted Life Years (DALYs) per person or across a population are a simple way to assess the health damage related to a disease, as they take into account the decrement to both length and quality of life that a person experiences as a result of the condition in question.
A total of 58 pertinent papers were identified. In addition to looking directly for information fulfilling at least one of our four defined parameters, we also noted additional information, such as other outcomes measured and the population sub-group studied.
Unfortunately, the low amount of evidence available means it's difficult to make claims with certainty. The results of our search demonstrated that iron deficiency anaemia, a key outcome of iron deficiency, was associated with a considerable and detrimental impact upon health. For instance, one study reported that the total global burden due to iron deficiency anaemia in 2004 was over 35 million DALYs.s Our spreadsheet containing our data is available here.
It is important to bear in mind that iron deficiency is not the sole cause of anaemia, and anaemia is often used as an inappropriate proxy for iron deficiency anaemia. For example, anaemia can also be caused by other factors, such as P. falciparum malaria. In 2009, WHO estimated that 60% of anaemia was due to iron deficiency in non-malarial areas and 50% in malarial areas.
While not all of the information located fell neatly into our defined parameters, it was evident that simple interventions can have a major impact on health. For example, one report estimated that providing 50% of the global population with iron fortification would increase health by 59 million DALYs and ion supplementation would increase health by 59 million DALYs, when implemented over a 10-year period.
Real life studies support this impressive estimate as realistic. A 21% reduction in perinatal mortality was seen in Africa after iron supplementation at a cost of only $16.59 over a year per pregnant woman, and fortification cost only $0.13 per person. Put into context, the average cost-effectiveness of iron supplementation and fortification at 95% coverage in Africa was $66 and $20 per DALY averted, respectively. These values are significantly below the widely accepted DALY cost-effectiveness threshold proposed by the World Bank of $150 per DALY for an intervention to qualify as an "attractive" investment for a low income country.
Whilst researching, it became clear that sub-groups are affected differently by iron deficiency, with pregnant women and infants the most severely impacted, due to higher iron demands. For example, one study demonstrated that iron deficiency was responsible for 0.4% of all deaths in South Africa, but 7.4% of all deaths of pregnant women. Indeed, many of the studies only considered the sub-groups of mothers and infants, or provided separate figures for them. Further investigation is warranted, as the data for the sub-groups could be weighted by their proportion of the overall population to give a more accurate picture of the total health impact.
Again, these conclusions should be looked at with a note of caution due to lack of evidence. The results are generalized from just a few epidemiological studies, and further investigation is warranted. But it does seem like that the large number of preventable DALYs caused by iron deficiency, as highlighted by our research, is just one piece of evidence in the mounting case for further action against the condition. Intervention could be promising as it could prevent large numbers of deaths as well as increasing the productivity of the workforce; in fact, annual productivity losses due to iron deficiency are thought to amount to approximately 0.57% of GDP in developing countries.
There is a silver lining. Iron deficiency may be the "most common preventable nutritional deficiency", but with the facts on the cost-effectiveness and health benefits of interventions laid out, one can but hope that its days as holder of that title are numbered.
By Ruth McElhone, working pro bono on behalf of Costello Medical Consulting, with Robert Wiblin
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