Longitudinal Follow-Up of a Population with MCI: Predictive Value of the MIS Test with Delayed Recall for Progression to Dementia

Mild Cognitive Impairment (MCI) is a condition of cognitive decline which is more pronounced than cognitive decline which characterizes normal aging. It causes a slight but noticeable and measurable decline in cognitive abilities, including memory and thinking skills. There is evidence showing that suffering from MCI poses a high risk of conversion to Alzheimer’s Disease (AD), which is the most frequent cause of dementia.

Impairment in verbal episodic memory, and in particular in a delayed recall phase, is considered one of the early markers of progression from mild cognitive impairment (MCI) to dementia. Therefore, having cognitive screening instruments with predictive value for progression is of utmost importance. The purpose of this work was to show the predictive value, sensitivity and specificity of the Memory Impairment Screen with delayed recall (MIS-DR) to predict conversion to dementia in patients with MCI. 

The study included 502 consecutive patients over 60 years of age, evaluated between January 2009 and July 2012, in the Older Adult Functional Evaluation Unit of Hospital Italiano de Buenos Aires, who sought consultation about cognitive complaints, with a clinical diagnosis of mild cognitive impairment (MCI). They were followed up to assess conversion to dementia. 

The results showed that during follow-up, 144 participants developed dementia (28.6%, 95% CI 24.76 - 32.85) and the average time of progression to dementia were 23 months (SD 13.2). The cut-off point was established below 6 for MIS-DR and it showed a sensitivity of 76% (95% CI 68.77 - 77.84) and a specificity of 56% (95% CI 50.44 - 61.58), with a positive predictive value of 41% (95% CI 34.78 - 47.6) and a negative predictive value of 85% (95% CI 80.53 - 91.11) for predicting progression to dementia. Of those patients who obtained a MIS-DR score below 6, 41% developed dementia, in contrast to 14.53% of those with a score above or equal to 6, OR 4.09 (95% CI 2.64 - 6.34), p < 0.00001. There were no significant differences in terms of gender, education level or vascular risk factors among patients who converted and those who did not convert to dementia. 

In conclusion, the authors believe that MIS-DR is a useful and valid test to detect episodic memory impairment and to identify patients at risk of progression to dementia. Future work on this line of research will focus on establishing the characteristics of the type of dementia that patients develop with greater specificity, and on the identification of other early cognitive makers.

Article by Labos Edith, et al, from Argentina.

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