Scientists from the University of Melbourne and Australian National University studied 6,560 people living in Canberra or neighboring Queanbeyan. The study confirmed that carriers of the APOE4 gene type (allele), which confers higher risk for Alzheimer’s, are just like other people their age throughout most of adult life in terms of core mental functions. Previous findings had been unclear.
The study may help rule out the possibility of very early Alzheimer’s as the cause of the declines among carriers before they reach old age. Lead author Anthony Jorm said: “Although some areas of cognitive decline begin from early adulthood onwards, this is not due – as some have speculated – to very early Alzheimer’s changes in the brain.”
This finding suggests that APOE4 heightens the risk for Alzheimer’s in old age through an additional, as-yet-unknown process that accelerates or intensifies normal changes, pushing them into the range of disease. Jorm provides an analogy. “In general, hair becomes thinner with age,” he says. “However, there are some people who have an additional hereditary factor that makes them bald at an early age.”