According to lead study author Dr. Esther J.M. de Brouwer, from the Department of Geriatrics at the University Medical Center in Utrecht, in the Netherlands, "We know that calcifications in the hippocampus are common, especially with increasing age."
Dementia and the hippocampus
Other causes of dementia include damage to the blood supply to the brain, buildup of abnormal proteins called Lewy bodies, and inflammation.
However, Dr. de Brouwer and team note that current dementia research on the hippocampus tends to focus on degeneration of brain cells and tissues as opposed to abnormalities in the blood supply, or vascular system, that feeds them.
The scientists' findings could be significant because they support the idea that the "calcifications may be of vascular origin."
New type of CT scan
A distinguishing feature of the study is that it was able to take advantage of a new type of scan known as a "multiplanar brain CT scan."
This type of CT scan lets radiologists differentiate between calcium buildup in the hippocampus and that in neighboring structures such as the choroid plexus.
Dr. de Brouwer explains that this scan type also "makes it possible to see the hippocampus in different anatomical planes; for example, from top to bottom, right to left, and front to back."
The team examined the multiplanar brain CT scans of around 2,000 people who had attended a hospital memory clinic in the Netherlands during 2009–2015. The age of the patients ranged between 45 and 96 years. Their average age was 78.
The CT scans had all been performed as part of diagnostic tests that also included assessment of cognitive function.
The researchers had two goals in mind for their study. One was to investigate any links between risk factors known to cause vascular problems — such as smoking, diabetes, and high blood pressure — and hippocampal calcifications.
The other goal of the study was to discover whether calcium buildup in the hippocampus has an effect on cognitive function.
Smoking and diabetes 'likely risk factors'
When they analyzed the CT scans, the scientists found that 19 percent of all the study participants had calcifications in their hippocampus.
They also discovered that "older age," smoking, and diabetes "were associated with the presence of hippocampal calcifications."
The study design did not permit the scientists to be sure that smoking and diabetes actually raise the risk of hippocampal calcifications.
However, Dr. de Brouwer says that they "do think that smoking and diabetes are risk factors."
There is evidence to suggest that hippocampal calcifications are a hallmark of vascular disease and "[i]t is well-known that smoking and diabetes are risk factors for cardiovascular disease," she adds.
No link to cognitive function
The team was puzzled that the study found no links between calcium buildup in the hippocampus and cognitive function.
Dr. de Brouwer suggests that this could have been due to some of the limitations of their methods and design.
One limitation, for example, was the fact that there was no "control group" of healthy subjects; all the participants were patients at a memory clinic and had disorders ranging from cognitive impairment to vascular dementia and Alzheimer's disease.
Another explanation might lie in the fact that there are several layers in the hippocampus, "and it is possible that the calcifications [found in the study] did not damage the hippocampal structure that is important for memory storage," notes Dr. de Brouwer.
She and her colleagues are now expanding the research to include other groups in a bid to better understand how calcium buildup in the hippocampus might impact cognitive function.
"It is [...] likely that smoking and diabetes are risk factors for hippocampal calcifications."
Dr. Esther J. M. de Brouwer