Factors Associated with Lower Cognitive Performance Scores Among Older Japanese Men in Hawaii and Japan.

Background: Few studies have compared factors related to cognitive function among people with similar genetic backgrounds but different lifestyles.

Objective: We aimed to identify factors related to lower cognitive scores among older Japanese men in two genetically similar cohorts exposed to different lifestyle factors.

Methods: This cross-sectional study of community-dwelling Japanese men aged 71-81 years included 2,628 men enrolled in the Kuakini Honolulu-Asia Aging Study based in Hawaii and 349 men in the Shiga Epidemiological Study of Subclinical Atherosclerosis based in Japan. We compared participant performance through Cognitive Abilities Screening Instrument (CASI) assessment in Hawaii (1991-1993) and Japan (2009-2014). Factors related to low cognitive scores (history of cardiovascular disease, cardiometabolic factors, and lifestyle factors) were identified with questionnaires and measurements. Multivariable logistic regression analysis was used to calculate the adjusted odds ratios (ORs) of a low (< 82) CASI score based on different factors.

Results: CASI scores were lower in Hawaii than in Japan [21.2%(n = 556) versus 12.3%(n = 43), p < 0.001], though this was not significant when adjusted for age and educational attainment (Hawaii 20.3%versus Japan 17.9%, p = 0.328). History of stroke (OR = 1.65, 95%confidence interval = 1.19-2.29) was positively associated with low cognitive scores in Hawaii. Body mass index ≥25 kg/m2 tended to be associated with low cognitive scores in Japan; there was a significant interaction between the cohorts.

Conclusion: Cognitive scores differences between cohorts were mostly explained by differences in educational attainment. Conversely, cardiovascular diseases and cardiometabolic factors differentially impacted cognitive scores among genetically similar older men exposed to different lifestyle factors.