In the search for what causes and signals Alzheimer's disease, scientists have often looked to genes. New evidence, however, points to gender.
More men than women had memory problems by middle age, a new study found. Men had smaller hippocampal brain regions than women — a region of the brain tied to memory.
Clifford R. Jack, Jr., MD, of the Mayo Clinic in Rochester, MN, led this study.
Alzheimer's disease is a brain disease that slowly destroys memory and thinking skills. Deposits of small abnormal proteins, called B-amyloids in the brain are common in this disease. This study found that changes in the structure of the brain and memory changes may be tied to aging and gender and not to B-amyloid deposits.
"Our findings are consistent with a model of late-onset Alzheimer's disease in which B-amyloidosis arises later in life," Dr. Jack and team wrote.
These researchers studied more than 1,200 people aged 30 to 95 years old. Memory, hippocampal size and B-amyloid deposits in the brain were measured.
Dr. Jack and team also examined patients for the presence of a gene called APOE ɛ4. People with APOE ɛ4 may face an increased risk for developing Alzheimer's later in life.
Memory got worse as people aged from 30 to 90, Dr. Jack and team found. Hippocampal size decreased gradually from ages 30 to 60, then faster after age 60.
Memory was worse in men than in women. Also, hippocampal size was smaller in men than in women.
APOE ɛ4 was tied to increased B-amyloid deposits only in people older than 70.
Charles Decarli, MD, of the Department of Neurology and Center for Neuroscience at the University of California at Davis, wrote an editorial about this study.
"One particularly striking result was the rather dramatic changes in both hippocampal volume and memory performance seen before 65 years," Dr. DeCarli wrote.
The study by Dr. Jack and colleagues provided valuable insight into the processes future studies should investigate, Dr. DeCarli said.
"Understanding the basic biology of these early processes is likely to substantially inform us about ways in which we can maintain cognitive health and optimize resistance to late-life dementia," Dr. DeCarli wrote.
The study and editorial were published March 16 in JAMA Neurology.
The National Institute on Aging and the Alexander Family Alzheimer Disease Research Professorship of the Mayo Foundation funded this research. Study author Dr. David S. Knopman served as deputy editor for the journal Neurology.