Midlife Use of Written Japanese and Protection From Late Life Dementia

Abstract

Background The cognitive reserve hypothesis would predict that use of written Japanese should confer protection against dementia because of the complexity of its ideograms compared with written English. We sought to test this hypothesis in analyses from a longitudinal study of Japanese-American men. Methods Participants were second-generation Japanese-American men (Nisei) on the island of Oahu, Hawaii, who were seen in 1965 and in subsequent examinations to detect dementia beginning in 1991-1993. Use of spoken and written Japanese was self-reported in 1965 (Analyses 1 and 2), and mid-life use of written Japanese and written English was self-reported in 1994-1996 (Analysis 3). We analyzed prevalent dementia outcomes in 1991-1993 (Analysis 1, n=3,139) using logistic regression, and incident dementia outcomes in 1994-2002 (Analysis 2, n=2,299) and in 1997-2002 (Analysis 3, n=1,655) using Cox proportional hazards regression. Dementia outcomes included all-cause dementia, probable and possible Alzheimer disease, and probable vascular dementia. We adjusted models for probable and possible confounders. Results Participants who reported proficiency with written Japanese were older and had lower incomes. For Analysis 1, there were 154 prevalent cases of dementia, 74 of Alzheimer disease, and 43 of vascular dementia; for Analysis 2, 236 incident cases of dementia, 138 of Alzheimer disease, and 45 of vascular dementia; and for Analysis 3, 125 incident cases of dementia, 80 of Alzheimer disease, and 20 of vascular dementia. There was no relationship in adjusted models between self-reported proficiency with written Japanese and any dementia outcomes. Conclusions Proficiency with written Japanese does not appear to be protective for dementia.

The Protective Effect of Cantonese/Mandarin Bilingualism on the Onset of Alzheimer Disease

“…This discrepancy might be caused by the self-reported and less accurate questionnaire about physical activities we utilized. Hypertension, type 2 diabetes, smoking, and urban living environment were not correlated with age at AD onset, which is similar to the results of other studies [5, 7, 23, 24]. …”

Does bilingualism shape inhibitory control in the elderly?

“…While some researchers do not support this potential consequence of bilingualism when the characteristics of the samples are carefully controlled for (see Chertkow et al, 2010;Lawton et al, 2015), others report significant results even in carefully matched groups (see Alladi et al, 2013;Woumans et al, 2015). However, as correctly stated by Paap et al (2015b), the most compelling pieces of evidence at this regard may come from longitudinal studies following cohorts of individuals, and most of these studies yielded non-significant differences, or even monolingualfavoring trends (e.g., Crane et al, 2009;Lawton et al, 2015;Sanders et al, 2012;Yeung, St. John, Menec, & Tyas, 2014;Zahodne et al, 2014), while only one presented evidence in favor of a bilingual advantage at this level of analysis (Wilson, Boyle, Yang, James, & Bennett, 2015).…”

“…As a potential solution for the conundrum presented by the unclear debate of the role of bilingualism in patients with dementia, a handful of studies have opted for a longitudinal approach, testing cohorts starting from a baseline stage in which no signs of dementia are evident. Most of the studies using this approach have shown no consistent delay in the onset of the symptoms caused by bilingualism (Crane et al, 2009;Lawton, Gasquoine, & Weimer, 2015;Sanders, Hall, Katz, & Lipton, 2012;Yeung, St. John, Menec, & Tyas, 2014;Zahodne, Schofield, Farrell, Stern, & Manly, 2014).…”

Does bilingualism contribute to cognitive reserve? Cognitive and neural perspectives.

“…Yet, they did not find bilingualism to delay onset of dementia even in the group with lower years of formal education. A strength of this study, as well as of the ones by Crane and colleagues (2009, 2010), is the fact that the data was longitudinal, which may reduce recall bias and also permits a more objective measure of incident dementia. Nevertheless, the authors acknowledged several limitations that might account for the findings.…”