The effects of childhood residence in Japan and testing language on cognitive performance in late life among Japanese American men in Hawaii

OBJECTIVES: To examine the association of years spent in Japan during child hood with cognitive test performance in late life among Japanese American m en, and to assess the influence of the language used for testing on this as sociation. DESIGN: A cross-sectional study. SETTING/PARTICIPANTS : A total of 3734 Japanese American men, aged 71-93 ye ars, who were first- or second-generation migrants and living on Oahu Islan d, Hawaii. MEASUREMENTS: The outcome variable was cognitive test performance assessed using the Cognitive Abilities Screening Instrument (CASI), which was develo ped for cross-cultural studies of cognitive impairment. The explanatory var iable of main interest was the number of years spent in Japan during school -age childhood years (ages 6-17). The associations of CASI scores with chil dhood years in Japan was evaluated using a stepwise multiple linear regress ion model in which a total of 40 potential confounders were included as cov ariates. RESULTS: In the total sample, there was an inverse association between CASI scores and middle childhood years in Japan. This association remained sign ificant after controlling for age, education, socioeconomic status, traditi onal Japanese food consumption, pulmonary function, apolipoprotein E4, prof iciency in speaking Japanese, and other possible confounders. When data wer e analyzed separately for subgroups according to the language preferred at testing (English or Japanese), associations between childhood years in Japa n and CASI scores were in opposite directions negative for the group tested in English and positive for the group tested in Japanese. The interaction between the testing language and childhood years in Japan was statistically significant. CONCLUSIONS: There was an inverse association between years spent in Japan during school-age years of childhood and cognitive test performance in late life. This association could not be accounted for by age, education, or ot her confounding factors. However, this finding was not observed in particip ants who preferred being tested in Japanese. To assess cognitive test perfo rmance in older people, it is of prime importance to use the most optimal l anguage for testing, usually the subject's native language.