Characteristics of Agraphia in Chinese Patients with Alzheimer's Disease and Amnestic Mild Cognitive Impairment

BACKGROUND: Patients with Alzheimer's disease (AD) manifest progressive decline in writing abilities. Most studies on agraphia in AD have been performed in the alphabetic system, such as English. However, these findings may not be applicable to other written language systems. The unique features of the Chinese written script could affect the patterns of agraphia in Chinese AD patients. The aim of this study was to explore the features of writing errors in Chinese patients with AD and amnestic mild cognitive impairment (a-MCI), as well as to study the relationship between their writing errors and neuropsychological functions. METHODS: In this study, we performed an observational study in a group of subjects including 17 AD patients, 14 patients with a-MCI, and 16 elderly healthy controls. We analyzed the writing errors in these subjects and also studied the relationship between their writing errors and neuropsychological functions. RESULTS: Our study showed that in patients whose mother tongue is Chinese, writing ability was comparatively well preserved in the MCI phase but significantly impaired when the disease progressed to the stage of AD. The writing errors showed corresponding increase with the severity of cognition decline, both in the types of errors and rate of occurrence. Analysis of the writing errors showed that word substitution and unintelligible words were the most frequent error types that occurred in all the three study groups. The occurrence rate of unintelligible words was significantly higher in the AD group compared with the a-MCI group (P = 0.024) and control group (P = 0.018). In addition, the occurrence rates of word substitution were also significantly higher in AD (P = 0.013) and a-MCI groups (P = 0.037) than that of control group. However, errors such as totally no response, visuospatial impairment, paragraph agraphia, ideograph, and perseverative writing errors were only seen in AD group. Besides, we also found a high occurrence rate of visuoconstructional errors (13.3%) in our AD group. CONCLUSIONS: Our study confirmed that agraphia is an important feature in patients with AD. The writing error profile in patients whose native language is Chinese was unique compared to patients using the alphabetic language system.