A new study reports that the ApoE4 gene, previously reported to be over-represented among patients with late onset Alzheimer's disease, appears to be a risk factor only among patients who developed the disease before age 70. The study examined 679 patients from 310 families and found that the gene was a strong predictor of risk only in individuals who had inherited two copies of the gene and who developed symptoms between the ages of 61 and 65. However, some individuals with two ApoE4 genes showed no symptoms well into their 80s. In an interview with the New York Times, Dr. Tanzi, the leader of the team that carried out the study, said genetic screening tests based on identifying the ApoE4 gene "should not be used as a screening test to predict the disease in anyone, even in families where you see a clustering of Alzheimer's." The findings indicate that other environmental or genetic factors, as yet unknown, play an important role in determining risk for Alzheimer's disease. The study, by Blacker, et al., was published in Neurology.—June Kinoshita
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- Blacker D, Haines JL, Rodes L, Terwedow H, Go RC, Harrell LE, Perry RT, Bassett SS, Chase G, Meyers D, Albert MS, Tanzi R. ApoE-4 and age at onset of Alzheimer's disease: the NIMH genetics initiative. Neurology. 1997 Jan;48(1):139-47. PubMed.