The Protective Effect of Cantonese/Mandarin Bilingualism on the Onset of Alzheimer Disease.
Several studies have found that bilingualism can delay the age of onset of Alz-heimer disease (AD). The interpretation of these findings is that switching between two languages can enhance cognitive reserve. However, some studies have provided inconsistent results. Diverse language pairs used by the bilinguals in different studies may contribute to the discrepancies. Cantonese and Mandarin are widely used in southern China, and regarded as bilingualism. The present study aims to determine if Cantonese/Mandarin bilingualism can delay the onset of AD. The data of 129 patients diagnosed with probable AD, including 48 Cantonese monolinguals, 20 Mandarin monolinguals, and 61 Cantonese/Mandarin bilinguals were analyzed. Cantonese/Mandarin bilinguals were found to have an older age at AD onset, and older age at the first clinic visit than Mandarin monolinguals and Cantonese monolinguals. Both Mandarin monolinguals and Cantonese/Mandarin bilinguals had a higher education level and higher occupation status than the Cantonese monolinguals. Mandarin monolinguals did not differ from Cantonese/Mandarin bilinguals significantly in years of education and occupation status. The multiple linear regression analyses indicated that Cantonese/Mandarin bilingualism can delay the onset of AD independently. Constantly speaking both Cantonese and Mandarin from at least early adulthood can delay the onset of AD.