Degree of bilingualism predicts age of diagnosis of Alzheimer's disease in low-education but not in highly educated Hispanics

• Published in: Neuropsychologia 2011-12, Vol.49 (14), p.3826-3830
• Main Authors: Gollan, Tamar H., Salmon, David P., Montoya, Rosa I., Galasko, Douglas R.
• Format: Article
• Language: English
• Subjects: Adult and adolescent clinical studies; Age Differences; Age Factors; Age of Onset; Aged; Aged, 80 and over; Alzheimer Disease - diagnosis; Alzheimer Disease - psychology; Alzheimers Disease; Bilingualism; Biological and medical sciences; Clinical Diagnosis; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Dementia; Dementia onset; Education; Educational Attainment; Educational Status; English; Female; Hispanic; Hispanic Americans; Hispanic Americans - psychology; Humans; Interaction; Language Proficiency; Male; Medical sciences; Multilingualism; Names; Neurological Impairments; Neurology; Neuropsychological Tests; Organic mental disorders. Neuropsychology; Predictor Variables; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Scores; Spanish Speaking
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/j.neuropsychologia.2011.09.041

► Objectively measured degree of bilingualism predicts age-of-diagnosis of Alzheimer's disease. ► Spanish–English bilinguals with probable AD. ► Significant effect obtained only in low education groups. ► Bilingualism along a continuum increases cognitive reserve. The current study investigated the relationship between bilingual language proficiency and onset of probable Alzheimer's disease (AD) in 44 Spanish–English bilinguals at the UCSD Alzheimer's Disease Research Center. Degree of bilingualism along a continuum was measured using Boston Naming Test (BNT) scores in each language. Higher degrees of bilingualism were associated with increasingly later age-of-diagnosis (and age of onset of symptoms), but this effect was driven by participants with low education level (a significant interaction between years of education and bilingualism) most of whom (73%) were also Spanish-dominant. Additionally, only objective measures (i.e., BNT scores), not self-reported degree of bilingualism, predicted age-of-diagnosis even though objective and self-reported measures were significantly correlated. These findings establish a specific connection between knowledge of two languages and delay of AD onset, and demonstrate that bilingual effects can be obscured by interactions between education and bilingualism, and by failure to obtain objective measures of bilingualism. More generally, these data support analogies between the effects of bilingualism and “cognitive reserve” and suggest an upper limit on the extent to which reserve can function to delay dementia.