Abstract
In this study we evaluated the ability of elderly people to comprehend Japanese grammar in order to investigate the influence of aging and cognitive impairment on language ability. The cognitive ability of 55 participants with a mean age of 78.4 years was evaluated with a Japanese version of the Mini-Mental State (MMS) test. Their grammatical ability was evaluated using a J.COSS test (JWU's, Japanese Test for Comprehension of Syntax and Semantics). The results revealed that the older group (75-99 years) demonstrated more cognitive impairment and grammatical errors than the younger group (60-74 years). In accordance with the MMS test norm for cognitive disorders (a score of 23 or less), most of the cognitive impairment group was able to understand a two-item combination sentence; however, they had difficulty with comprehension of particles and conjunctions. Moreover, comprehension of complex-syntax-structured sentences was influenced by both aging and cognitive impairment. Although previous studies have not shown any influence of age-related decline in lexical knowledge on language ability, the present study revealed a deterioration in grammatical knowledge influenced by aging and cognitive impairment in old age. Because of this evidence that age-related decline in language processing is in some cases due to an age-related decline in the working memory, the findings suggest that a grammatical deficit with age may be associated with frontal lobe function.
