Dementia, through its many forms, inflicts a significant burden on the estimated XNUMX million people that live with it worldwide, as well as on their caregivers.
Some level of cognitive decline is to be expected as a normal part of aging. Dementia, however, takes this decline one step further, progressively affecting memory, thinking, orientation, calculation, learning capacity, comprehension, and judgement .
Continuous struggles exist to not only discover new and better treatment options but also to find the right indicators to predict what kind of cognitive impairment a person may experience later on in life.
A study published in June by Daniel E. Gustavson et al.  in Neurology set out to examine the ability of specific cognitive tests to predict mild cognitive impairment in healthy adults. Authors focused on episodic memory and semantic fluency as potential predictors, as well as the interaction between the two.
. Interestingly, they chose a particular lot of participants – twins from the Vietnam Era Twin Registry, selected from men who had served in the US military between 1965 and 1975. Aged between 51 and 59 at recruitment, they were considered representative of American men in their age group but also allowed for some genetic factors to be investigated.
Standardized neuropsychological tests were performed to quantify episodic memory and verbal fluency, as well as the cognitive status, at the beginning of the study and again after a period of 6 years. Only participants with a normal cognitive status at inclusion were selected.
Of the XNUMX participants, XNUMX developed some form of mild cognitive impairment (MCI) over the XNUMX-year period – about half of which progressed to amnestic MCI. These participants seemed to only differ from their peers in one respect – they were older than those who remained cognitively normal.
When examining the proposed predictors, authors found that progression to MCI was predicted by poor scores in both semantic fluency and episodic memory at the beginning of the study. Episodic memory performance in particular seemed to predict progression to amnestic MCI, although semantic fluency played a non-negligible role as well.
Episodic memory, but not necessarily semantic fluency, seemed to also predict non-amnestic MCI, suggesting it can oversee the decline in general cognitive ability, rather than just in areas that are directly related to speech.
Another interesting feat is that semantic fluency and memory seemed correlated. This feat was found to be primarily explained by genetic factors, since they varied similarly in matched twins. Furthermore, authors rely on previous research to stipulate that these genetic influences may overlap with the genetic risk factors for Alzheimer’s disease. However, further research involving imaging and molecular studies is needed for these hypotheses to be clarified.
Authors conclude that episodic memory and semantic fluency should be regarded as risk factors for cognitive decline in normal individuals. While the importance of biological markers for diagnoses (such as a PET-CT result) cannot be negated, they point out that neuropsychological tests were often found to be a better and earlier predictor of cognitive decline and progression to Alzheimer’s disease.
An ideal approach would likely combine the benefits of biomarkers with those of fluency and memory measures to predict cognitive decline in healthy individuals.
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