Gene Posing Risk for Alzheimer's Doesn't Affect Mental Aging

Wednesday, January 10, 2007; 12:00 AM

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WEDNESDAY, Jan. 10 (HealthDay News) -- Having a gene that increases the risk of Alzheimer's disease doesn't contribute to cognitive changes during most of adulthood, Australian researchers say.

The APOE gene helps transport cholesterol through the production of apolipoprotein E. People carry two copies of APOE, each being one of four APOE alleles, or types. Having the APOE4 allele increases the risk of developing Alzheimer's disease.

Researchers from the University of Melbourne and Australian National University set out to determine whether people who carry at least one copy of APOE4 are cognitively different from people who do not carry the allele.

The study, published in the January issue of Neuropsychology, involved 6,560 people who were enrolled in the PATH Through Life Project, a long-term study of aging that assesses people in age groups of 20-24, 40-44, and 60-64 years, every four years for a period of 20 years.

The researchers studied whether, in each age group, carriers of APOE4 were different on tests of functions affected by Alzheimer's disease, including episodic memory, working memory, mental speed, reaction time and reading vocabulary.

As expected, performance on all tests (except for reading vocabulary, which tends to hold up with age) declined across the age groups -- a sign of normal cognitive aging. But APOE4 did not affect performance, which indicates that people with APOE4 age normally in those cognitive functions, at least between ages 20 and 64.

According to the researchers, this finding suggests that APOE4 heightens the risk for Alzheimer's disease later in life through an unknown process that accelerates or intensifies normal cognitive changes.

More information

The Administration on Aging has more about Alzheimer's disease.