ToK: Sickle Cell Anemia & Prevalence of Malaria

There is a link between sickle cell anemia and prevalence of malaria.

How can we know whether there is a causal link in such cases or simply a correlation?

15 thoughts on “ToK: Sickle Cell Anemia & Prevalence of Malaria

  1. It is often hard to distinguish between causal link and correlation because there is a fine line that is hard to find. Often the terms causation and correlation are interchangeable but in this case they have different meanings. Correlation between A and B means that given that A is present there is a strong chance that B is present. Whereas causation means that given that A is present B is also present. Extensive testing has to be conducted to be able to identify if something is causation or just correlation. Causation will be thought to be the case until one case comes up that shows that A does not equal B.

  2. The link between sickle cell anemia and prevalence of malaria is difficult to determine whether if its just a casual link or a correlation. Different case studies have been made in order of proving the correlation of this. In order to prove that there a correlation or a casual link should depende on the percentage of participants that shows they have less chances or they are inmune to malaria because of having sickle cell anemia. Furthermore, researchers should take into consideration if they are cases of people suffering from sickle cell anemia who also had malaria.

  3. Research has shown that sickle cell anemia cases are most common in areas where there is high exposure to malaria. This may, at first, seem as a casual link. But, in fact, it has shown that the descendants of African Americans have evolved to developing immunity to this disease. This supported Darwin’s theory if evolution, where there is survival of the fittest. So over time, in order to minimize the casualties, sickle cell anemia formed in, most commonly, African American descendants in order to protect them from this disease. Patients with sickle cell anemia have sickle shaped RBC, which doesn’t provide the desired shape for the malaria parasite to take over the cells. On the other hand, sickle cell anemia does not only benefit these people exposed to malaria, but also has risks of its own. As the cells are sickle, oxygen levels are restricted and therefore less oxygen will travel to the organs in the body. Along with that, it makes the blood sticky and therefore results to the clotting of the blood and the clogging of the vessels.

  4. Correlation does not imply causation, a word uttered in statistics everyday, but what does it mean? When analysing statistics in the area of knowledge Mathematics, we can sometimes see a relation in where when one variable increases or decreases the second variable mimics its behaviour or reverses it, this is what is known as correlation. When using the deductive this is usually regarded as one variable leading to the changes in another variable, i.e. attributing the change as causation. This is an error done by most people when interpreting data. When looking at sickle cell anaemia and malaria we see that those carrying the heterozygote gene for SCA have lower malaria infection rates, we can positively assume the two variables are correlated, however, we cannot completely be sure that one causes the other. It is highly unlikely that the malaria decrease causes a higher gene frequency, as the RBs mutation is epigenetic. Thus researchers have attributed the increase in the heterozygote gene frequency to the decrease in malaria, as they believe that the abnormal shape hinders infections. This is a plausible explanation, however, since ni independent studies have been done that show that there is no other =extraneous variables that causes both decreased malaria and increased heterozygote RBs, then this cannot be fully attributed as causation. People might argue that through reason and intuition since there is a strong correlation it mist be causation, this is an impulse we must learn to control as scientist; the number of lemons imported from Mexico has a .99R2 correlation value to the amount of motorway accidents in Minnesota, it does not mean that lemons cause car crashes.

  5. Sickle cell anemia is an inherited form of anemia; a condition in which there aren’t enough healthy red blood cells to carry adequate oxygen throughout your body.
    Normally, your red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anemia, the red blood cells become rigid and sticky and are shaped like sickles or “boomerangs”. A good way to remember the disease could be “boomerang cell disease” for those who struggle remembering it.
    These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.
    Several studies suggested that, in one way or another, sickle hemoglobin might get in the way of the Plasmodium parasite (Malaria parasite) infecting red blood cells, reducing the number of parasites that actually infect the host and thus conferring some protection against the disease.the sickle mutation may have been naturally selected in sub-Saharan Africa, where malaria is endemic and one of the major causes of death. Similarly, other clinically silent mutations may have been selected throughout evolution, for their ability to provide survival advantage against Plasmodium infection (Malarian infection).


  6. Possible link between sickle cell anamia and prevalence of Malaria has been researched over years, and have now been firmly established through number of clinical field studies from different parts of Africa. This experimental work was conducted on over 500 population in Africa, and its results have shown strong consistency between the blood disease and infectious disease, and thus concluded it as a plausible mechanism. From this research, we have concluded that heterozygous infected red cells are removed by macrophages, and are immune to maleria. On the other hand, patient who are homozygous are susceptible to sickle gene and will suffer from SCA and malaria.
    The choice of whether such pattern was a causation or a correlation has been discussed. By causation, they are implying that those with sickle cell disease will be the only ones immune to maleria, and that there is a definite proof to support this. However, we are still in process of discussing the actual process behind this correlation. Therefore, it is better to say thhat although there is a definite correlation between cases of maleria and sickle cell disease, it is inconclusive and whether weak or strong does not mean causal relationship.

  7. We can know whether there is a causal link in such malaria and sickle cell anemia cases or simply a correlation by carrying out studies in malaria prone areas such as Africa. Such studies can include a prospective surveillance study that looks at different types of malaria in patients, and their causes, and then at sickle-cell anemia in patients, in the same area, as well as patients without it. In one study, the prevalence of malarial parasitemia was found to be lower in patients with Sickle cell anemia than in patients without Sickle cell anemia in children in Africa. By comparing statistics of patients who suffer from both diseases or either or none, we can usually either make a link between them or discover that it is merely a correlation.

  8. A correlation in science is used to formulate a hypothesis, therefore a discovery of the correlation it self can not be used as an evidence itself.Correlation usually tell us the mutual relationship of two or more things. Causality is the relation of the cause and effect. Where a correlation exists, it may or may not be due to a casual link.Sickle cell anemia is where there is a mutation in the genes when the 6th codon is mutated from GAG to GTG. This causes the haemoglobin to attach together in tissues with low concentration of oxygen. The allele of sickle cell is recessive but is also codominat. Meaning that having one allele may provide a sickle cell trait. It is a fact that having sickle cell anemia will make an individual resistant to malaria but also can be fatal. We can conclude that the gene for sickle cell allows the resistance to malaria. It is possible that the allele for the sickle cell arose in mutation but adapted to being resistant to malaria.Thus, the mutation has been established in areas where malaria is common. ( Africa, Mediterranean area of Europe). Therefore, sickle cell anemia does not cause infection with malaria but sickle cell disease is caused by a mutation that resulted as a resistance to malaria.

  9. It cannot be simply correlation as a correlation is used to formulate a hypothesis rather than pure evidence. This hypothesis must then be tested in order to know if an empirical relationship exists between sickle cell anemia and the prevalence of malaria. Correlation must be distinguished from cause and effect, and to do this one must differentiate whether both sickle cell anemia and the prevalence of malaria were caused for a logical reason without any underlying causes. If this is not the case then there is a correlation but no casual link. The frequency of the sickle cell allele is correlated with the prevalence of malaria in many different parts of the world, therefore this could mean that there is a casual link. This is because there has been a clear sign of natural selection in favor of the sickle cell allele in areas that are malaria ridden. Natural selection has therefore led to certain frequencies of the sickle cell alleles and the normal hemoglobin alleles to balance out the risk of anemia and malaria, this is therefore a cause and effect relationship.

  10. Correlation is a mutual relationship or connection between two or more things. In this case, it is the degree to the correlation between the prevalence of malaria and sickle cell anemia. A causal link is where the one variable has a direct impact on another variable
    In many parts of the world, the frequency of sickle cell anemia and of malaria is correlated. One of the criteria that can be used to distinguish this is the cause and effect. Cause and effect is the principle of causation. It is making something occur, or is the underlying reason why something happened. Research has proved that there is a correlation between the frequency of sickle cell anemia and malaria – proving that there IS a casual link. Due to this research, scientists can hypothesize that there has clearly been natural selection in favor of the sickle-cell allele especially in malaria ridden areas, despite this causing severe anemia to red blood cells.
    Therefore, in order to distinguish the correlation, cause and effect were used to differentiate whether this correlation exists for a particular or logical reason. And if there is no reason, there is most likely no correlation.

  11. Sickle cell anemia is only advantageous in regions of the world where the incidence of malaria is high and it occurs much less in regions/areas where the populations are rarely exposed to malaria – this is because since sickle cell anemia is disadvantageous in regions with little to no malaria exposure, those with sickle cell anemia pass on their trait less often. In addition, the biochemical evidence suggests that when malarial parasites inhabit a red blood cell, it induces the cell to sickly by the Bohr effect – this gives an individual with sickle cell anemia or the sickle cell trait resistance to malaria. This biochemical and demographical evidence very much suggests that there is a relationship between the two. However that is all the evidence tell us. More research would need to be conducted to figure our whether the relationship is a casual link or a correlation.

  12. Sickle cell anemia is when there is a mutation in the genes when the sixth codon is mutated from GAG to GTG. When this allele is transcribed, the mRNA now has GUG as its sixth codon. When this amino acid is coded for, it creates valine instead of glutamic acid. This causes hemoglobin molecules to become sticky and would stick together in tissues with low oxygen concentrations. The hemoglobin molecules distort the red blood cells into a sickle shape. The frequency of the sickle-cell allele is correlated with the prevalence of malaria in many parts of the world. Therefore, there is a causal link as the independant variable has a direct impact on the dependant variable. Natural selection is involved in this situation as it is in favour of the sickle-cell allele in malaria ridden areas, despite it causing severe anemia to red blood cells. Natural selection has led to particular frequencies of the sickle-cell and the normal hemoglobin alleles, to balance the risks of anemia and malaria.

  13. There is a correlation between the prevalence of sickle cell anemia and the prevalence of malaria. Sickle cell anemia is a recessive conditions, and carriers of the sickle cell disease have a protective advantage against malaria. Therefore, the frequency of sickle cell anemia carriers are high in regions where malaria is endemic.

    Correlation is the relationship between two variables where causation is when one variable causes another. Correlation does not imply causation. In science, it is very difficult to isolate variables and define a cause-and-effect relationship. Therefore there is a correlation between sickle cell anemia and malaria rather than a cause-and-effect relationship.

  14. When a correlation between two things is found, it is used to formulate a hypothesis. This hypothesis can then be tested in order to find out whether or not there is an underlying reason for which they have a relationship. Global distribution shows that there are areas with high frequencies of both sickle cell anemia and prevalence of malaria. The majority of these areas are in Africa. A hypothesis could be tested in those areas in order to see whether or not there is a correlation.

  15. In the area of knowledge of the ‘Human Sciences’, correlational studies are not explicitly used as evidence to formulate and prove scientific hypothesises as done in the area of knowledge of ‘Mathematics’. Thus ‘statistical correlation’ in science is not used to imply causations but are used as a basis to test for hypothesises of a cause-and-effect relationship. For example, in the case of sickle cell anaemia and malaria it was hypothesised that due to the presence of the malaria parasite the patient was persistent of acquiring sickle cell anaemia. This hypothesis has to be further tested to see if an underlying empirical relationship exists.

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