title: Bilingualism does not alter cognitive decline or dementia risk among Spanish-speaking immigrants.
abstract: OBJECTIVE
  Clinic-based studies suggest that dementia is diagnosed at older ages in bilinguals compared with monolinguals. The current study sought to test this hypothesis in a large, prospective, community-based study of initially nondemented Hispanic immigrants living in a Spanish-speaking enclave of northern Manhattan.
  
  
  METHODS
  Participants included 1,067 participants in the Washington/Hamilton Heights Inwood Columbia Aging Project (WHICAP) who were tested in Spanish and followed at 18-24 month intervals for up to 23 years. Spanish-English bilingualism was estimated via both self-report and an objective measure of English reading level. Multilevel models for change estimated the independent effects of bilingualism on cognitive decline in 4 domains: episodic memory, language, executive function, and speed. Over the course of the study, 282 participants developed dementia. Cox regression was used to estimate the independent effect of bilingualism on dementia conversion. Covariates included country of origin, gender, education, time spent in the United States, recruitment cohort, and age at enrollment.
  
  
  RESULTS
  Independent of the covariates, bilingualism was associated with better memory and executive function at baseline. However, bilingualism was not independently associated with rates of cognitive decline or dementia conversion. Results were similar whether bilingualism was measured via self-report or an objective test of reading level.
  
  
  CONCLUSIONS
  This study does not support a protective effect of bilingualism on age-related cognitive decline or the development of dementia. In this sample of Hispanic immigrants, bilingualism is related to higher initial scores on cognitive tests and higher educational attainment and may not represent a unique source of cognitive reserve.
authors.affiliation: Cognitive Neuroscience Division, Department of Neurology and Taub Institute for Research on Alzheimer's Disease and The Aging Brain, Columbia University.
authors.forename: Laura B
authors.initials: LB
authors.lastname: Zahodne
authors.affiliation: Centre for Translational Neuroscience and Mental Health, University of Newcastle.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Schofield
authors.affiliation: Cognitive Neuroscience Division, Department of Neurology and Taub Institute for Research on Alzheimer's Disease and The Aging Brain, Columbia University.
authors.forename: Meagan T
authors.initials: MT
authors.lastname: Farrell
authors.affiliation: Cognitive Neuroscience Division, Department of Neurology and Taub Institute for Research on Alzheimer's Disease and The Aging Brain, Columbia University.
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Stern
authors.affiliation: Cognitive Neuroscience Division, Department of Neurology and Taub Institute for Research on Alzheimer's Disease and The Aging Brain, Columbia University.
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Manly
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003072:Cognition Disorders / Q000208:ethnology*; D003704:Dementia / Q000208:ethnology*; D018450:Disease Progression; D054242:Emigrants and Immigrants; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D008297:Male; D008875:Middle Aged; D019303:Multilingualism; D012307:Risk Factors