Cognitive reserve in Parkinson's disease: the effects of welsh-english bilingualism on executive function.

John V Hindle,Alexandra J M Bastable,Kirstie L Pye,Ellen Bialystok,Christopher J Whitaker,Fergus I M Craik,Enlli M Thomas,Linda Clare,Anthony Martyr,Virginia C Mueller Gathercole,Pamela A Martin-Forbes

doi:10.1155/2015/943572

Abstract

Objective. Bilingualism has been shown to benefit executive function (EF) and delay the onset of Alzheimer's disease. This study aims at examining whether a bilingual advantage applies to EF in Parkinson's disease (PD). Method. In a cross-sectional outpatient cohort of monolingual English (n = 57) and bilingual Welsh/English (n = 46) speakers with PD we evaluated the effects of bilingualism compared with monolingualism on performance on EF tasks. In bilinguals we also assessed the effects of the degree of daily usage of each language and the degree of bilingualism. Results. Monolinguals showed an advantage in performance of language tests. There were no differences in performance of EF tests in monolinguals and bilinguals. Those who used Welsh less in daily life had better performance on one test of English vocabulary. The degree of bilingualism correlated with one test of nonverbal reasoning and one of working memory but with no other tests of EF. Discussion. The reasons why the expected benefit in EF in Welsh-English bilinguals with PD was not found require further study. Future studies in PD should include other language pairs, analysis of the effects of the degree of bilingualism, and longitudinal analysis of cognitive decline or dementia together with structural or functional neuroimaging.

Highlights

The theory of cognitive reserve has been proposed to explain the mismatch between the degree of brain pathological changes and observable clinical manifestations [1], in relation to the development of dementias such as Alzheimer’s disease (AD) [2], and to account for interindividual rates of cognitive decline
Bilingualism is a form of cognitive reserve which may delay the onset of AD [5, 6] but it has not been studied in Parkinson’s disease (PD)
Demographic and Disease Variables. 57 monolingual English and 46 bilingual Welsh/English speakers with PD were recruited. 12 of the monolingual group had learnt some Welsh (2 from age 5, 2 from age 11, and 8 in adulthood) but did not fulfil the definition of bilingualism used in the study

Summary

Introduction

The theory of cognitive reserve has been proposed to explain the mismatch between the degree of brain pathological changes and observable clinical manifestations [1], in relation to the development of dementias such as Alzheimer’s disease (AD) [2], and to account for interindividual rates of cognitive decline. There has been recent interest in the effects of cognitive reserve in Parkinson’s disease (PD) [3, 4]. PD is an age-related neurodegenerative condition which is associated with cognitive impairment. Up to 25% of newly diagnosed people with PD who do not have dementia and up to 90% of people with PD at any stage experience mild cognitive impairment (MCI), with an increased risk of developing PD dementia (PDD) [7]. Cognitive impairment in PD is manifested in abnormalities of executive function (EF) [8], visuospatial function, attention, and memory. Impairment of EF in PD may, influence adversely quality of life, health status, and carer burden [9] and reduce awareness of functional limitations [10]

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Discussion

Conclusion