Scientists from the University of British Columbia have published a paper that argues that age at first onset of dementia (AD) may be a more important predictor of later dementia onset than cognitive impairment (CIO) or social isolation.
In a recent article published in the journal Current Psychiatry, the researchers compared the age at onset of AD (ADI) and the cognitive function of patients with CIO to patients with AD and CIO at various stages of dementia.
“It was surprising to see that the older the patient, the more ADI was related to later AD onset,” said lead researcher, Dr. James R. Smith.
“The most striking finding was that the higher the age of onset of the illness, the greater the correlation with AD.”
Smith said that the age difference in AD is a strong predictor of the risk of AD in people with Cio.
“This is important because people who have less cognitive impairment may have an increased risk of developing AD,” said Smith.
“Our findings suggest that the risk factor for later AD may be cognitive impairment, rather than AD.”
The researchers looked at data from the Canadian National Centre for Social Research’s ADI-CIO project, a longitudinal study that has followed more than 6,000 people from birth to death since 1989.
The study looked at people who were diagnosed with AD in childhood or in adulthood.
The data was collected over nearly eight decades and included interviews with more than 8,000 individuals who were followed up through age 64.
“There is growing evidence that the more cognitive impairment a person has, the higher their risk of later developing dementia,” said study co-author Dr. Lisa C. Schmitt, PhD. “This is consistent with what we know from previous studies, that AD patients with greater cognitive impairment are at increased risk for later dementia.”
Schmitt said the study looked specifically at the association between cognitive impairment and later dementia.
She said there is a growing body of evidence that cognitive impairment is associated with an increased likelihood of AD.
“We did not find a clear relationship between cognitive function and AD onset, but there was a significant association,” she said.
“It was interesting that the correlation was as strong for AD as for ADI.”
Schmidt said the correlation between cognitive functioning and AD may not be absolute, as some studies have suggested.
“One of the things we’re trying to do in our research is to see if there are any associations with AD between cognitive ability and cognitive impairment,” she added.
Schmitt added that although there is some evidence that dementia patients with cognitive impairment have a higher rate of early AD, there is no clear evidence that this is an absolute risk factor.
The researchers noted that a study published earlier this year in the Journal of Alzheimer’s Disease also showed that cognitive decline in the early stages of AD was linked to cognitive impairment in the late stages of the disease.
However, Schmitt said that her research was the first to show that cognitive function is a more potent predictor of dementia onset.
“Cognitive function is important, but we don’t know why,” she explained.
“We think it has to do with a number of things.”
The research was supported by the National Research Council, the National Institutes of Health, the Canadian Institutes of Research, the Canada Foundation for Innovation and Science, and the Canadian Foundation for Innovative Medical Research.