ABSTRACT
Objective:To characterize the digital language markers in Alzheimer′s disease (AD) and mild cognitive impairment (MCI) patients, and to explore the pathological effect and aging effect on these markers.Methods:AD ( n=14) and MCI ( n=16) patients from memory clinic in Peking Union Medical College Hospital, age-matched cognitively normal elderly adults ( n=18) and youthful adults ( n=19) as controls participated in the study. The digital speech data of animal fluency test were collected. Novel language markers such as response time, semantic similarity and word frequency were analyzed in addition to the traditional word production, clustering and switching indicators by trained professionals. Multiple linear regression analysis with multiple comparison was used to test the associations of language markers with the cognitive status, adjusting for education. Results:The results of multiple regression analysis showed that, after adjusting for the years of education, statistically significant differences existed in 11 language markers among the four groups ( P<0.001), except for the effective word production in the last 15 s, cluster size, the first word response time and the average semantic similarity. Compared to other three groups, AD group differed significantly in effective word production, effective rate, repetitive rate, effective word production in the first 15 s, the number of subcategories, single word production time and inter-subcategory switching interval ( P<0.001). In addition, compared to cognitively normal youthful group, AD group had less number of switching and shorter semantic maximum distance ( P=0.001, P<0.001); both AD and MCI groups had longer intra-subcategory switching interval ( P<0.001, P=0.001); AD, MCI and cognitively normal elderly groups had significantly higher word frequency ( P<0.001); MCI group had significantly less number of effective word production and subcategories ( P=0.002, P=0.003); both MCI and cognitively normal elderly groups had significantly longer single word production time ( P<0.001). Conclusions:The performance of AD patients on the semantic fluency test task was affected by both pathological effect and normal aging effect. Pathological indicators included effective word production, effective rate, repetition rate, effective word production in the first 15 s, the number of subcategories, inter-subcategory switching interval and single word production time. These results provide a new approach to identify the specific effects of AD dementia.