ORIGINAL ARTICLE Bilingual proﬁciency and cognitive reserve in Persian–English bilingual older adults Zahra Jafari • Mahdiye Esmaili • Reyhaneh Toufan • Maryam Aghamollaei Received: 6 September 2014 / Accepted: 28 October 2014 Ó Springer International Publishing Switzerland 2014 Abstract Background and aims More than genetic and physical inﬂuences, different environmental stimuli affect brain reserve, and bilingualism is one example. In this study, effect of bilingual proﬁciency on older adult’s cognitive reserve was investigated. Methods Persian and English versions of the Word Association Test were used among 26 educated older adults with a mean age of 67.52 years who became bilin- gual in Persian–English early in life. Lexical memory and Bergen dichotic listening tests were performed. Results The bilingual proﬁciency score in all participants was within the range for early bilingualism. The Persian version of Word Association Test content validity index was 98.17 %. The inter-rater reliability for the Persian version of Word Association Test was 0.980, and that for the English version was 0.986. In addition, the intra-rater reliability for the Persian version was 0.857, and that for the English version was 0.954 (p \ 0.001). There was signiﬁcant correlation between the frequency of words expressed in the English Word Association Test and years for which English has been spoken as a second language (p B 0.045). A signiﬁcant correlation was observed between the bilingual proﬁciency score and lexical mem- ory score (p \ 0.043). Bilingual proﬁciency score also showed a signiﬁcant correlation with the dichotic listening scores in all three non-forced, forced-right, and forced-left attention situations (p B 0.045). Conclusions These results demonstrated the inﬂuence of bilingualism on shaping cognitive reserve in Persian– English bilingual older adults, representing linguistic experience-dependent neuroplasticity. Keywords Word association test Á Older adult Á Cognitive reserve Á Bilingual proﬁciency Á Lexical memory Á Dichotic listening Introduction Bilingual or multilingual individuals are those who sys- tematically use two or more languages in everyday life [1]. Acquisition of a second language confers distinct enhancements in the neural encoding of auditory stimuli [2, 3]. Although studies have shown the impact of bilingualism in adulthood, its greatest effect is realized in old age when it protects individuals against cognitive decline, a concept that is interpreted as ‘‘cognitive reserve’’, and the role of bilingualism in postponing the symptoms of dementia has been conﬁrmed [4, 5]. Z. Jafari (&) Department of Basic Sciences in Rehabilitation, School of Rehabilitation Sciences, Iran University of Medical Sciences (IUMS), Nezam Alley, Shahnazari St, Mother Sq, Mirdamad Blvd, PO Box 15875-4391, Tehran, Iran e-mail: jafari.z@iums.ac.ir Z. Jafari Rehabilitation Research Center (RRC), Iran University of Medical Sciences (IUMS), Tehran, Iran Z. Jafari Á M. Esmaili Iranian Research Center on Aging, University of Social Welfare and Rehabilitation Sciences (USWR), Tehran, Iran R. Toufan Department of Audiology, School of Rehabilitation Sciences, Iran University of Medical Sciences (IUMS), Tehran, Iran M. Aghamollaei Department of Audiology, School of Rehabilitation, Tehran University of Medical Sciences (TUMS), Tehran, Iran 123 Aging Clin Exp Res DOI 10.1007/s40520-014-0288-x