Variability in performance: Identifying early signs of future cognitive impairment

Objective: The current study examined whether year-to-year variability in cognitive performance differbetween individuals cognitively unimpaired and individuals who subsequently develop dementia.Method: Analyses included a case-control sample of Baltimore Longitudinal Study of Aging (BLSA;mean [M] age = 69.90, standard deviation [SD] = 8.92) participants. One hundred and 35 clinicallydiagnosed demented participants were matched with 135 nondemented participants based on age at initialtesting and sex. Cognitive performance was examined using measures of memory, executive function,attention, language, and global mental status performance. Cognitive performance was examined frombaseline to 5 years before cognitive impairment (M, assessments = 3.03, SD = 2.80). Results: Ascompared with unimpaired individuals, individuals diagnosed with dementia had greater variability onmeasures of attention, executive function, language, and semantic memory at least 5 years before theestimated onset of cognitive impairment, which may be indicative of maladaptive cognitive functioning.The dementia cases, however, had less variability on visual memory than the unimpaired group, whichmay suggest that these cases had more difficulty learning. Conclusions: These results demonstrate thatperformance variability indexed over annual or biennial visits may be useful in identifying early signs ofsubsequent cognitive impairment.