Uninherited Alzheimer’s disease is a common form that usually affects older people, whereas the much rarer, inherited form – also known as early onset Alzheimer’s – strikes people much earlier in life, sometimes as young as 30 or 40. Now, a new study led by Washington University in St. Louis, MO, finds there are networks in the brain that are affected in a similar way by both forms of the disease.
Reporting the findings in the journal JAMA Neurology, the international team suggests that in both inherited and uninherited forms of Alzheimer’s, the same basic component of brain function begins to decline about 5 years before symptoms such as memory loss become obvious.
“The brain networks affected by inherited Alzheimer’s disease in a 30-year-old are very similar to the networks affected by uninherited Alzheimer’s disease in a 60-, 70- or 80-year-old. This affirms that what we learn by studying inherited Alzheimer’s, which appears at younger ages, will help us better understand and treat more common forms of the disease.”
The feature that the team says breaks down in both forms of the disease is what is termed “functional connectivity,” where the activity levels of networked brain regions rise and fall in step with each other. Scientists believe this type of coordination helps brain regions work together, and also to stay out of each other’s way, during mental activity.
Prof. Ances says checking functional connectivity could be a useful way to monitor how treatments are working as the disease moves from the early stages to the emergence of more obvious symptoms:
“Right now, this period when functional connectivity begins breaking down is a time when family and loved ones may start noticing little changes in personality or mental function in someone with the disease, but not significant enough changes to cause real alarm,” he explains.
The team hopes in the future it will be possible to ensure treatment has begun well in advance of these types of changes, “we want to slow or stop the damage caused by Alzheimer’s years earlier,” Prof. Ances says.
Scientists have already established that some of the proteins that become problematic in early onset Alzheimer’s also cause problems in the more common form that usually appears in older people.
They also believe there are more similarities between the two forms of the disease, but it is not an easy subject to research, hampered by two challenges in particular: finding enough people with inherited Alzheimer’s to study, and the fact both forms of the disease progress slowly.
With the first challenge in mind, Washington University’s Charles F. and Joanne Knight Alzheimer’s Disease Research Center started an international network for studying families with inherited, early onset Alzheimer’s disease. Set up 5 years ago, the Dominantly Inherited Alzheimer’s Network, or DIAN, has now enrolled nearly 400 families.
To meet the second challenge, the research center has also been collecting extensive data from long-term studies of aging, such as the Healthy Aging and Senile Dementia Study, which has been going for over 30 years.
Brain scan data from these two initiatives has been sufficient to allow the study authors to compare functional connectivity in the two forms of Alzheimer’s disease. To study functional connectivity, researchers need the results of brain scans taken as participants daydream.
Prof. Ances says they found the decline of functional connectivity appears to play a role in the middle stages of Alzheimer’s disease. But that is not where you want to look for an initial diagnosis, because you want to treat the disease before it gets to that stage.
So while the findings may not help with early diagnosis, what they suggest, says Prof. Ances, is that “functional connectivity may help us track the progression of Alzheimer’s in patients who are first diagnosed when they’re beginning to show early signs of dementia.”
Meanwhile, from another recently published study by researchers in Australia, Medical News Today learned how some areas of the brain may not slow down with aging, but remain as effective as they are in youth.