Preferential preservation of visuospatial memory over verbal memory in the Old Order Amish

Background: While studying cognition in the Old Order Amish (OOA), we have observed strong performance on the constructional praxis delayed recall (CPDR) as compared to other cognitive tests, independent of overall cognitive status. This may indicate a preferential preservation of visuospatial memory in this population. Here, we investigate this by comparing the CPDR to the word list delayed recall (WLDR) within the OOA, as well as by comparing these results to a non-Amish cohort. Method: 420 OOA individuals in Indiana/Ohio age 66-95 who had complete data for the CPDR and WLDR were included. From the non-Amish CERAD cohort, 401 individuals age 60-96 with the same tests were included. For both cohorts, education-adjusted Z-scores were calculated for the CPDR and WLDR. The difference between the CPDR Z-score and the WLDR Z-score was calculated as a measure of the preservation of visuospatial memory over verbal memory. T-tests were first used to compare the tests within both cohorts and then stratified by case/control status. Linear regression was then used to investigate the effects of age, sex, cognitive status, and cohort on the Z-scores and difference between Z-scores. Additional t-tests and regressions were then performed to further investigate the effect of sex and its interaction with cohort. Result: We found a significantly better performance on CPDR over WLDR in every cognitive status group in the OOA, but not in all groups of the CERAD cohort. After controlling for age, sex, and cognitive status, this preferential preservation remains significantly higher in the Amish, with being in the Amish cohort increasing the difference between Z-scores by an average of 0.615 units when compared to being in the CERAD cohort. When adjusting for age, sex, cognitive status, and cohort, the interaction between cohort and sex is significant, with the Amish males exhibiting a greater difference between Z-scores compared to other groups, with a significant interaction value of 0.676. Discussion: Overall, these findings suggest that the OOA preferentially preserve visuospatial memory over verbal memory, regardless of cognitive status. This effect is particularly strong in OOA males. In summary, this study gives additional evidence that the Amish exhibit unique patterns of memory loss and aging, with a preferential preservation of visuospatial memory over verbal memory. Additional studies are needed to further explain this phenomenon.