Abstract
Dementia is a global public health priority which cost global societies $818 billion in 2015 and is disproportionately impacting low and middle-income countries (LMICs). With limited availability of disease modifying drugs to treat Alzheimer's disease (AD), researchers have increasingly focused on preventative strategies which may promote healthy cognitive aging and mitigate the risk of cognitive impairment in aging. Lifelong bilingualism has been presented as both a highly debated and promising cognitive reserve factor which has been associated with better cognitive outcomes in aging. A recent metanalysis has suggested that bilingual individuals present on average 4.05 years later with the clinical features of AD than monolinguals. Bilinguals are also diagnosed with AD ~2.0 years later than monolingual counterparts. In this perspective piece we critically evaluate the findings of this metanalysis and consider the specific implications of these findings to LMICs. Furthermore, we appraise the major epidemiological studies conducted globally on bilingualism and the onset of dementia. We consider how both impactful and robust studies of bilingualism and cognition in older age may be conducted in LMICs. Given the limited expenditure and resources available in LMICs and minimal successes of clinical trials of disease modifying drugs we propose that bilingualism should be positioned as an important and specific public health strategy for maintaining healthy cognitive aging in LMICs. Finally, we reflect upon the scope of implementing bilingualism within the education systems of LMICs and the promotion of bilingualism as a healthy cognitive aging initiative within government policy.
Highlights
Twenty first century societies are rapidly transitioning to aging populations which are often characterized by a burden of age related conditions such as dementia [1]
We critically review bilingualism as a cognitive reserve factor and examine the key studies of bilingualism explored in both high income countries (HICs) and low and middle countries (LMICs)
We propose that incorporating bilingualism into dementia public health policy to delay the onset of dementia is an important and specific strategy in maintaining healthy cognitive aging in LMICs
Summary
Twenty first century societies are rapidly transitioning to aging populations which are often characterized by a burden of age related conditions such as dementia [1]. This systematic review reported findings from eight studies which examined the relationship between bilingualism and the age of onset of dementia Metanalysis from these studies determined that bilinguals [53] with AD presented with delayed clinical features (694 individuals; mean difference MD 4.05 years; 95% CI:1.87–6.22) and are diagnosed (1,012 participants: MD 2.0 years; 95% CI 0.08–3.92) [23]. In this study the age of diagnosis was measured between bilinguals and monolinguals and determined that amongst bilinguals with behavioral variant FTD the age of onset of dementia was 5.7 years later in bilinguals 62.6 vs 56.5 p = 0.006 in monolinguals [69] This finding was independent of the similar case mix factors as observed in the 2007 Hyderabad study [69]. A validation study of the OCS-Plus in a South African study sample in which 45% of the sample did not have any formal education revealed that the OCS-Plus had excellent construct and external
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