The influence of age on cognitive test performance as measured by the original and extended version of the Alzheimer’s disease assessment scale in the SIU longitudinal cognitive aging study

Background Since the 1980s, the Alzheimer’s Disease Assessment Scale (ADAS) has been used to evaluate cognitive aging in Alzheimer’s disease (AD) and is considered the gold standard for assessing the efficacy of medications for treatment of AD. One criticism of the original ADAS (oADAS) is that this measure is not sensitive to pre‐dementia syndromes such as mild cognitive impairment (MCI). Previous studies have found that increasing age is associated with poorer neuropsychological functioning. In the present study, we examined the influence of age on the oADAS. We hypothesized that increasing age would be associated with increased error scores on both the oADAS and an extended version of this measure (eADAS) after controlling for gender and education. Method We included data from 938 adults who were enrolled in the SIU Longitudinal Cognitive Aging Study (LCAS) as normal controls. The vast majority of the cohort was White/Not‐Hispanic (98.9%) and female (72.4%). Mean age and education were 67.3 years and 14.9 years, respectively. Participants who met the diagnostic criteria for MCI, dementia, and/or other neurological or psychiatric conditions at baseline or developed these conditions within three consecutive study visits were excluded. The oADAS was administered using standardized methods. The eADAS included short‐delay recall and recognition trials for the first word‐list, a short‐delay true‐false word recognition trial for the second word‐list, a letter‐digit timed psychomotor test, supermarket fluency, spontaneous clock drawing, three additional items to the object naming subtest, three additional figures to copy, and a similarities test. Result The mean oADAS and eADAS scores were 3.9 and 8.7, respectively. Linear regression analysis revealed that both gender and education were associated with higher error scores for both the oADAS and eADAS (p < 0.001). After controlling for gender and education, increasing age was also found to be associated with higher error scores for both the oADAS and eADAS (p < 0.001). Conclusion Our results are consistent with previous literature showing age effects on oADAS scores and also extend these findings to the eADAS. Future research determining the sensitivity of the extended ADAS to the transition from normal aging to MCI and dementia are ongoing.