GMAT Reading Comprehension (RC) | Although some progress has been made in the last two decades

Although some progress has been made in the last two decades on the treatment of Alzheimer’s disease, the causes of the disease are still largely unknown. A recent study conducted by the National Institute of Aging (NIA) appears to have found new evidence concerning the origins of Alzheimer’s. Scientists who carried out the study at NIA focused on the correlation between a patient’s genetic history, which scientists usually agree is the basis of Alzheimer’s, and the onset of Alzheimer’s. The evidence cited by the NIA team includes the identification of the apolipoprotein E (APOE) as the specific gene that may be responsible for the onset of Alzheimer’s. The APOE gene can be sub-divided into many different forms, but the NIA research team has identified one specific form of APOE, the APOE ?4 gene, as a very likely cause of Alzheimer’s.
The presence of APOE ?4 is known to make an individual particularly vulnerable to both cognitive and vascular dysfunction,which are among the chief symptoms of Alzheimer’s.

However, a review of the study and its results by the Center for Disease Control and Prevention (CDC) maintains that the evidence discovered by the NIA may not necessarily indicate that the APOE ?4 gene is responsible for Alzheimer’s.
CDC experts have pointed out that APOE ?4 is known to cause conditions such as cardiac disease and diabetes in patients who have no genetic history of Alzheimer’s and are not considered at risk for the disease.
Further, the CDC review team has observed that APOE ?4 has been found in individuals who show no symptoms of Alzheimer’s.
In response to the CDC’s review, the NIA team has pointed out that the APOE ?4 gene may be dormant in some individuals, suggesting that the absence of Alzheimer’s in individuals who have the APOE ?4 gene cannot be used as evidence to rule out this gene as the cause of Alzheimer’s disease.