Los Angeles, California – Despite widespread use of a single term, Alzheimer’s disease is actually a diverse collection of diseases, symptoms and pathological changes. What’s happening in the brain often varies widely from patient to patient, and a trigger for one person may be harmless is another.
In a unique study, an international team of researchers led by USC psychologist Margaret Gatzcompared the brains of twins where one or both died of Alzheimer’s disease. They found that many of the twin pairs not only had similar progressions of Alzheimer’s disease and dementia prior to death, but they also had similar combinations of pathologies — two-or-more unconnected areas of damage to the brain.
The paper is part of Gatz’s landmark body of work on aging and cognition with the Swedish Twin Registry, a large cohort study of more than 14,000 Swedish twins, now over the age of 65. Across nearly 30 years, Gatz’s work with twins — including genetically identical pairs — has shifted the study of Alzheimer’s disease to include the entire lifespan, including the effects of developmental exposure, periodontal disease, mental health, obesity and diabetes on later-life Alzheimer’s risk.
The current paper provides more evidence that there may not be a single smoking-gun cause of Alzheimer’s, but rather a range of potential causes to which we may be susceptible largely depending on our genetics. It appears in the current issue of the journal Brain Pathology.
“We try to make inferences based on tests and diagnoses, but we have to assume that what we’re seeing is a manifestation of what’s going on in these twins’ brains,” said Gatz, professor of psychology, gerontology and preventive medicine in USC Dornsife College. “For this reason, we wanted to compare the brains of twins to ask whether identical twins’ brains are actually more identical?”
The researchers had the rare opportunity to directly autopsy the brains of seven pairs of twins who both died after being receiving diagnostic evaluations over many years, including a pair of identical twins who were both diagnosed with Alzheimer’s and died within a year of one another at the age of 98.