Self‐rated daily language use, more than self‐rated bilingual language competency, moderates the effects of brain on cognition in a Hispanic cohort

Abstract

AbstractBackgroundSome studies suggest that bilingualism may be associated with better cognition but the impact of bilingualism versus language practice on cognition and brain integrity is not well understood. Here, bilingualism encodes the knowledge of one language or two while language use encodes daily language practice (predominantly English or Spanish, or daily use of both). In a Hispanic cohort, we the assess effects of language variables on cognitive outcomes of baseline and longitudinal executive function and episodic memory, incorporating brain measures, age, gender, and education, and also whether they moderate the relationships between cognition and the MRI markers of brain integrity.MethodA baseline Hispanic cohort (N = 100) with a single MRI scan and a longitudinal subset (N = 73) with serial scans were sampled from the UC Davis Aging and Diversity cohort (Table 1). Linguistic measures were based on self‐reports. They were bilingualism, and among bilingual participants, daily language use. Baseline and longitudinal executive and memory were modeled by regressions incorporating age, education level, brain signature regions, and language variable ‐ first for bilingualism in the entire cohort and then for language use restricted to the bilinguals.ResultBilingualism was not a significant predictor of baseline outcomes and there were no moderations with brain variables (Table 2). Among bilinguals, English‐only speakers showed significantly increased association of gray matter (Table 3) to memory compared to those who daily spoke Spanish or both languages. Longitudinally, bilingualism had no direct or moderating effects on cognitive change (Table 4). Bilinguals speaking primarily English had significantly increased association of atrophy signatures with both cognitive changes compared to Spanish or speakers of both languages (Table 5).ConclusionResults suggest a complex pattern of moderation of brain atrophy effects on cognitive decline in self‐reported bilinguals depending on whether daily language use is predominantly English, Spanish, or both. Bilinguals who spoke predominantly English were more susceptible to brain atrophy effects in comparison with those who used both languages or predominantly Spanish. These results have important implications for understanding how bilingualism relates to cognitive reserve but require replication in larger and different samples.