Bilingualism and Aging: Implications for (Delaying) Neurocognitive Decline

Abstract

As a result of advances in healthcare, the worldwide average life expectancy is steadily increasing. However, this positive trend has societal and individual costs, not least because greater life expectancy is linked to higher incidence of age-related diseases, such as dementia. Over the past few decades, research has isolated various protective “healthy lifestyle” factors argued to contribute positively to cognitive aging, e.g., healthy diet, physical exercise and occupational attainment. The present article critically reviews neuroscientific evidence for another such factor, i.e., speaking multiple languages. Moreover, with multiple societal stakeholders in mind, we contextualize and stress the importance of the research program that seeks to uncover and understand potential connections between bilingual language experience and cognitive aging trajectories, inclusive of the socio-economic impact it can have. If on the right track, this is an important line of research because bilingualism has the potential to cross-over socio-economic divides to a degree other healthy lifestyle factors currently do not and likely cannot.

Bilingualism with minority languages: Why searching for unicorn language users does not move us forward

“…Claiming an effect as an advantage entails a qualification that depends largely on specific perspectives and interpretations of results (Leivada et al, 2021). At present, most research suggests that certain bilingual experiences may relate to delaying the overt onset of symptoms (but not the underlying neurological damage) of some neurodegenerative diseases by as much as 4–5 years (see Antoniou, 2019; Gallo et al, 2022 for recent overviews). In a hypothetical future scenario in which there will be medical treatments which can stop progression of dementia and hence early detection becomes crucial, bilingualism will flip immediately from its current advantage position to the complete opposite because a delay in observing overt symptoms would entail a delay in early intervention and treatment (Leivada et al, 2021).…”

Bilingualism and Structural Network Organization in Temporal Lobe Epilepsy

“…This explanation fits with the prevailing view that the greatest benefits of bilingualism in dementia tend to be observed in executive control rather than in language or in medial temporal lobe networks directly affected by AD. 37,46,47 In B-LTLE, a modulated whole-brain network organization was associated with better task switching performance-a relationship not present in M-LTLE or in language performance. This lends additional support to the proposal that executive function is the domain that may be the most affected by dual-language experience and provides a functional correlate to whole-brain white matter network topology.…”

“…An exciting discovery is that bilingualism may serve as a neuroprotective factor in neurologic disease. 3,37 There is converging evidence of delayed diagnosis of dementia in bilinguals relative to monolinguals by an average of 4–5 years 2,4,5 (but see reference 38), as well as neuroprotective effects of bilingualism in primary progressive aphasia 39 and stroke. 40 However, little is known about the underlying neurobiological mechanisms.…”

“…For transitivity, the effect of bilingualism was present only in LTLE (F(1,113) = 10.57; p = 0.002; η p 2 = 0.09) and not RTLE (p = 0.147) such that B-LTLE had higher transitivity than M-LTLE (B-LTLE: mean46.19; 95% CI 45.68-46.71; M-LTLE: mean 45.21; 95% CI 44.91-45.52). The effect of bilingualism on path length was present in LTLE (F(1,113) = 4.79; p = 0.031; η p 2 = 0.04) and not RTLE (p = 0.276) such that B-LTLE had shorter path length than M-LTLE (B-LTLE: mean 69.27; 95% CI 68.68-69.85; M-LTLE: mean 70.02; 95% CI 69.67-70 37)…”

The Nuance of Bilingualism as a Reserve Contributor: Conveying Research to the Broader Neuroscience Community

“…As the brain is a plastic organ that adapts to varied demands over time, the mental exercise of bilingual language control reinforces the brain structurally and affords stronger functional connectivity across the lifespan (Perani and Abutalebi, 2015). Indeed, there is currently over a decade's worth of literature on neurocognitive adaptations in response to bilingualism, especially in aging populations where effects on CA trajectory and delayed onset of dementia/mild cognitive impairment (MCI) symptoms have been reported (see Gallo et al, 2022, for a recent review).…”