In a new study from the Cognitive Neurology Lab at the National Institute of Mental Health and Neuro Sciences in Bengaluru, India, researchers have uncovered evidence that speaking more than one language could be a key factor in safeguarding cognitive health in older adults. This research, led by Neurology Professor Suvarna Alladi and published in the journal Alzheimer’s & Dementia, points to bilingualism as a potential shield against dementia and mild cognitive impairment (MCI).
“Dementia is a growing public health concern that calls for a global action plan. While age is a strong predictor of developing dementia, life-course experiences such as higher education, engaging in physical activities, occupational complexity and more recently, bilingualism can reduce the risk of developing dementia through improving cognitive reserve/resilience,” explained study author Nithin Thanissery, a senior research fellow at the Cognitive Neurology Lab.
“India is uniquely suited for the study of bilingualism, cognition and dementia. The country has a socio-linguistically and culturally diverse non-immigrant population which speaks about 122 major languages. Bilingualism is the norm in most of the communities of India including Bengaluru, Karnataka state where the study was conducted. Bilinguals switch between languages frequently, engaging the executive and attentional control systems. The constant engagement of the cognitive and neural networks that makes bilingualism a strong contributor to cognitive reserve.”
“Following the initial report on bilingualism and its association with delaying the symptoms of dementia by Bialystok and colleagues (2007), we carried out a series of studies that consistently revealed protective effects of bilingualism against dementia (Alladi et al., 2013, 2016, 2017),” Thanissery explained.
Their new investigation into the protective effects of bilingualism involved a door-to-door community survey in the urban cohort of Jayanagar, South Bengaluru. This area, known for its linguistic diversity, became the focal point for gathering data on the prevalence of dementia and MCI among the elderly population. To ensure a broad and representative sample, the survey targeted individuals aged 60 and above, residing in the area for at least six consecutive months.
To accurately assess bilingualism, the research team used a modified version of the Language Use Questionnaire. This instrument allowed the researchers to rate language proficiency across multiple languages based on responses to a series of questions, estimating proficiency percentages. Cognitive assessments were then conducted in the language where participants achieved a proficiency score of 70% or higher.
Neuropsychological testing formed the backbone of the cognitive assessments. Instruments such as the Addenbrooke’s Cognitive Examination (ACE-III) were administered to evaluate general cognitive function, alongside other tests for diagnosing dementia and MCI. These assessments were performed at the participants’ homes by a trained team comprising clinical psychologists, speech-language pathologists, and neurologists, among others.
Upon analyzing the data from 1,234 participants, the study found that bilinguals constituted 65% of the cohort. A striking difference emerged in the prevalence rates of dementia and MCI between bilingual and monolingual participants. Dementia was notably less prevalent among bilinguals (0.4%) compared to monolinguals (4.9%), indicating a substantial reduction in risk for those who spoke more than one language.
Similarly, MCI was found in 5.3% of bilinguals, compared to 8.5% in monolinguals, further supporting the hypothesis that bilingualism serves as a protective factor against cognitive decline.
Bilingual individuals, including those with no cognitive impairment and those with MCI, demonstrated higher scores across various cognitive domains, including attention, memory, fluency, language, and visuospatial abilities, when compared to their monolingual counterparts.
“In a community setting in urban Bengaluru, we found that the prevalence of dementia and mild cognitive impairment were higher in those who spoke only one language than those who spoke more than one language,” Thanissery told PsyPost. “Bilingual older adults without any cognitive impairment had better cognitive functioning compared to their monolingual peers. These findings imply that promoting bi/multilingualism as cognitive reserve factor may potentially delay or slow down cognitive decline in the context of linguistically diverse communities with enriched language interactions.”
The results indicated that the protective effects of bilingualism persisted regardless of educational level, suggesting that the benefits of speaking multiple languages are not merely a reflection of higher education. Interestingly, the study also explored cognitive differences among individuals speaking two versus three or more languages, finding that while speaking more than one language offered a cognitive advantage, there was no significant additional benefit to knowing three or more languages.
However, the study is not without its limitations. The researchers acknowledge the challenge of accurately measuring language proficiency and the complexity of bilingualism itself, which varies widely in terms of proficiency levels, usage patterns, and the age at which additional languages are acquired. Additionally, the cross-sectional nature of the study means it can only show an association at a single point in time, not causality or long-term outcomes.
“We addressed the key methodological problems in earlier clinic and community studies related to bilingualism to a greater extent in the current study,” Thanissery said. “However, in order to understand the association between bilingualism, cognition and its protective effects, larger longitudinal studies need to be planned for the future.”
Such studies could provide more definitive evidence of bilingualism’s protective effects and shed light on the mechanisms behind these benefits.
“Our long-term goal is to understand how bilingualism is related to these protective effects against dementia,” Thanissery explained. “There have been several attempts to understand brain behavior correlates with healthy aging. Advancements in neuroimaging have allowed us to investigate the complexity of the structure and function of various regions of the brain which has given us a better understanding of dementia.”
“We also need to study the biomarkers such as beta-amyloid and tau associated with dementia in the realm of bilingualism. Moreover, we propose parallel investigations for a comprehensive understanding of the brain, cognitive mechanisms and social determinants of health linked with bilingualism. We believe that this holistic approach using multimodal methods in diverse sociolinguistic settings is essential for advancing knowledge in this field.”
“The impact of bilingualism in our study context were not influenced by sociodemographic characteristics such as education, occupation, and socioeconomic status,” Thanissery added. “Despite the fact that bilingualism in our study cohort independently influences cognition in old age and promotes healthy aging, this is likely to vary depending on the sociolinguistic context. This means that bilingual effects may vary depending on the sociolinguistic context in different populations.”
The study, “Protective effect of bilingualism on aging, MCI, and dementia: A community-based study,” was authored by Aparna Venugopal, Avanthi Paplikar, Feba Anna Varghese, Nithin Thanissery, Divya Ballal, Rakshith Maneshwar Hoskeri, Revathi Shekar, Binukumar Bhaskarapillai, Faheem Arshad, Vandana Valiyaparambath Purushothaman, Aravind Banavaram Anniappan, Girish Nagaraja Rao, and Suvarna Alladi.
