Background Cross-cultural studies of Alzheimer disease (AD) in genetically similar populations have been designed to detect possible environmental risk factors. It may be possible to perform similar analyses on a single population by examining acculturation, which is the extent to which individuals moving into a host society adapt to changes in lifestyle. Our objective was to determine whether acculturation to Western society was a risk factor for developing AD in an elderly population of Japanese-Americans.
Study Design and Methods A cohort of 1,622 dementia-free individuals with baseline acculturation scores was followed for 8 years with biennial cognitive screening assessments using the Cognitive Abilities Screening Instrument. Individuals scoring < 88 were given a full physical and neuropsychological evaluation. Diagnoses of dementia and AD were obtained by consensus agreement using criteria from the Diagnostic and Statistical Manual of Mental Disorders, 4th edition. Item response theory was used to combine 20 questionnaire responses to generate acculturation scores. Scores were divided into quartiles for analysis. Hazard ratios were calculated using the Cox proportional hazards model to determine the risk of AD for participants in high quartiles of acculturation versus those in low quartiles. We adjusted models for cardiovascular disease risk factors and demographic characteristics such as primary language and income.
Results In unadjusted models, the relative hazard associated with higher levels of acculturation was 0.6 (95% CI 0.4-0.97). With adjustments for demographic characteristics, the relative hazard associated with higher levels of acculturation was 1.84 (95% CI 0.5-6.6). With further adjustments for vascular disease risk factors and apolipoprotein E genotype, the relative hazard associated with higher levels of acculturation was 1.83 (95% CI 0.4-8.5).
Conclusion Japanese-Americans in the highest acculturation group appear to have an increased risk for acquiring AD, though the confidence interval includes the null value. This finding suggests further research to determine a biological rationale.
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