Multilingualism could be a means to guard against dementia. Dementia is a broad term used to describe the symptoms faced by people with brain dysfunctions or impairments; the symptoms are usually associated with “memory, language and thinking” (Medical News Today, 2014, p. 1). Alzheimer’s disease, which will be discussed in the section after, is the most common cause leading to dementia (World Health Organisation, 2012).
Compared to monolinguals, multilinguals have an advantage of several years’ delay before the onset of dementia (Alladi et al., 2013; Bialystok, Craik, & Freedman, 2007; Craik, Bialystok, & Freedman, 2010). The advantage extends to illiterate individuals too (Alladi et al., 2013).
Indian multilingual patients had an advantage of about four years before dementia developed, compared to monolinguals. However, within the study, there was no further advantage for those who spoke more than two languages (Alladi et al., 2013).
Research conducted by Bialystok et al. (2007) involving Canadian dementia patients indicated a later onset of 4.1 years for bilingual patients, as compared to monolingual patients, which is a significant difference. However, it is worthy to note that the “protective effect of bilingualism” may not be applicable to bilinguals with low proficiency in the second language (Bialystok et al., 2007, p. 462). The same researchers followed up with another study a few years later – bilingual immigrant patients were diagnosed 4.3 years later and reportedly experienced onset of cognitive impairment 5.1 years later than monolinguals (Craik et al., 2010).
As it is believed that the multilingual advantage could extend to language learners in their adulthood and beyond (Wanjek, 2013), more research can be done to verify whether and to what extent multilingualism benefits language learners of various ages against dementia. Future research could include how dementia patients from different countries (and thus linguistic environments) may experience different extents of benefits.
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Being bilingual could delay the onset of Alzheimer’s disease symptoms.
According to Diamond (2010), among Canadian elderly who were prone to Alzheimer’s disease, the bilingual elderly patients displayed initial symptoms 5 years older than monolingual patients. Considering the life expectancy of Canadians at 79, a 5 year delay means that there will be a 47% decreased probability that people in their seventies will even develop Alzheimer’s symptoms at all before their deaths (Diamond, 2010).
From a neurolinguistic perspective, a small proportion of patients with Alzheimer’s disease appear to have high levels of brain atrophy (loss of neurons) despite having relatively good cognitive function (Schweizer, Ware, Fischer, Craik, & Bialystok, 2012); this phenomenon has been widely linked to the ideas of “brain reserve” and “cognitive reserve” (Stern, 2002).
The following definitions may be helpful in understanding the expressions. Reserve can be defined as “amount of damage that can be sustained before reaching a threshold for clinical expression” in passive models and “differences in how the task is processed” in active models (Stern, 2002, p. 449).
According to Stern (2012), brain reserve refers to physical differences in the brain that may withstand changes due to diseases; whereas cognitive reserve refers to personal variation in how tasks are done, leading to some people being more robust than others.
With this understanding, it has been shown that bilinguals with Alzheimer’s disease had larger extents of brain atrophy, as compared to monolinguals performing at the same level cognitively, suggesting that bilingualism contributes to cognitive reserve of a person to function; thus assisting to counter the disease (Liu, Yip, Fan, & Meguro, 2012; Schweizer et al., 2012).
Future studies could investigate the relationship between how and when a person learns the second language and how this would influence the disease conditions of patients (Alladi et al., 2013). More research could be done to support or disagree with the notion that there are advantages against Alzheimer’s disease for people who speak more than two languages (Diamond, 2010).