Glossary: AD = AlzheimerÊs disease; MMSE = Mini-Mental State Examination.

Although evidence has accumulated validating the role of cognitive reserve in protecting against age-related dementias, 1 the relation between such factors as education and enhanced cognitive reserve is necessarily correlational. That is, it is unclear whether intellectual, social, and physical activities genuinely improve cognitive performance, or whether individuals with better-functioning brains (perhaps for genetic reasons) are more likely to perform well intellectually and are also protected naturally against the onset of dementia. This is not the case for bilingualism: in the vast majority of cases people become bilingual not because they are naturally gifted language learners, but because of circumstances that require it. The possibility that bilingualism may contribute to cognitive reserve and thus be associated with a delayed onset of dementia was suggested by a series of studies showing that the constant use of 2 or more languages enhances aspects of attention and cognitive control across the lifespan. 2ă4

This suggestion was explored in a previous study of hospital records of 184 patients diagnosed with dementia, of whom 91 were monolingual and 93 were bilingual. 5 Of these, 72% had been diagnosed with probable AlzheimerÊs disease (AD) and the remainder with other forms of dementia. At the time of the first clinic appointment, the 2 language groups did not differ in scores on the MiniMental State Examination (MMSE) or occupational status, but the monolingual group had received more education (12.4 years) than the bilingual group (10.8 years), a difference that should favor monolingual subjects. 6 However, the results showed that the estimated ages at onset of dementia were 71.4 years for monolingual subjects and 75.5 years for bilingual subjects; ages at first clinic appointment were 75.4 years for monolingual subjects and 78.6 years for bilingual subjects. Thus, bilingual patients exhibited symptoms of dementia between 3 and 4 years later than a comparable group of monolingual patients.