Bilingualism delays clinical manifestation of Alzheimer's disease

Abstract

The current study investigated the effects of bilingualism on the clinical manifestation of Alzheimer's disease (AD) in a European sample of patients. We assessed all incoming AD patients in two university hospitals within a specified timeframe. Sixty-nine monolinguals and 65 bilinguals diagnosed with probable AD were compared for time of clinical AD manifestation and diagnosis. The influence of other potentially interacting variables was also examined. Results indicated a significant delay for bilinguals of 4.6 years in manifestation and 4.8 years in diagnosis. Our study therefore strengthens the claim that bilingualism contributes to cognitive reserve and postpones the symptoms of dementia.

Beyond a simple “yes” and “no”

“…Similar results were reported in cognitive aging (n=232) (Perquin et al, 2013) and dementia (n=134) (Woumans et al, 2014). Thirdly, in large parts of the world bilingualism is the rule rather than exception.…”

The impact of bilingualism on brain reserve and metabolic connectivity in Alzheimer's dementia

“…Crucially, older bilingual individuals manifest symptoms of AD significantly later than comparable monolinguals (13)(14)(15), with an approximate delay of 4.5 y. Furthermore, bilingual speakers also show significantly better cognitive recovery following stroke than monolinguals (16).…”

Does Bilingualism Delay the Development of Dementia?

“…Conversely, retrospective studies which have investigated age of onset or diagnosis in individuals already diagnosed with the disease have typically reported that bilingualism delays the development of dementia (Alladi et al, 2013;Bialystok et al, 2007;Craik et al, 2010;Gollan et al, 2011;Woumans et al, 2015). Generally, prospective studies are preferred to retrospective studies as they are less affected by potential confounds such as recall bias, where individuals recall details incorrectly (Guzmán-Vélez & Tranel, 2015).…”

“…However, as Bialystok et al suggested (2007), there is no reason why bilinguals would be more likely to recall information differently to monolinguals. Furthermore, age of diagnosis was determined by medical records in these studies (Alladi et al, 2013;Bialystok et al, 2007;Craik et al, 2010;Gollan et al, 2011;Woumans et al, 2015), which are unlikely to contain false information. Nevertheless, further research is needed to explore why strikingly different findings have been reported using prospective and retrospective studies.…”

“…Indeed, in studies which have required participants to be highly proficient in their second language, bilingualism has been associated with delayed onset of symptoms and diagnosis (Bialystok et al, 2007;Craik et al, 2010;Woumans et al, 2015). However, in studies which have used more liberal definitions, non-significant differences have been reported (Zahodne et al, 2014).…”