The long-term memory sign: A clinical marker of functional cognitive disorders

This study examined the clinical utility of the long-term memory sign (LTMS), which is defined as self-reported long-term memory loss that is equal to or greater than self-reported short-term memory loss, and hypothesized to be a sign of functional cognitive disorders.

The LTMS was established using two standardized clinical interview prompts in 568 consecutive patients (M_AGE = 64.25, SD = 13.03) referred for neuropsychological evaluation. Patients were categorized into five diagnostic groups: dementia (n = 140), mild neurocognitive disorder (n = 245), primary psychiatric diagnosis (n = 100), subjective cognitive complaints with no diagnosis (n = 42), and invalid cognitive presentations (n = 41). The LTMS was analyzed as a marker of functional cognitive disorders using diagnostic accuracy indices.

The LTMS demonstrated high specificity (92.2%) but low sensitivity (28.3%) for functional cognitive disorders. It was reported by 82/568 patients (14.4%), with the highest frequency observed in those with invalid cognitive profiles (43.9%), primary psychiatric diagnoses (26.0%), and subjective cognitive complaints (19.0%), with progressively lower rates in mild neurocognitive disorder (9.8%) and dementia (4.3%).

The LTMS is a quickly elicited interview-based clinical sign that may reflect a neurologically unlikely subjective complaint pattern associated with functional cognitive disorders.