Illiteracy, dementia risk, and cognitive trajectories among older adults with low education.

OBJECTIVE: To investigate whether illiteracy was associated with greater risk of prevalent and incident dementia and more rapid cognitive decline among older adults with low education. METHODS: Analyses included 983 adults (≥65 years old, ≤4 years of schooling) who participated in a longitudinal community aging study. Literacy was self-reported ("Did you ever learn to read or write?"). Neuropsychological measures of memory, language, and visuospatial abilities were administered at baseline and at follow-ups (median [range] 3.49 years [0-23]). At each visit, functional, cognitive, and medical data were reviewed and a dementia diagnosis was made using standard criteria. Logistic regression and Cox proportional hazards models evaluated the association of literacy with prevalent and incident dementia, respectively, while latent growth curve models evaluated the effect of literacy on cognitive trajectories, adjusting for relevant demographic and medical covariates. RESULTS: Illiterate participants were almost 3 times as likely to have dementia at baseline compared to literate participants. Among those who did not have dementia at baseline, illiterate participants were twice as likely to develop dementia. While illiterate participants showed worse memory, language, and visuospatial functioning at baseline than literate participants, literacy was not associated with rate of cognitive decline. CONCLUSION: We found that illiteracy was independently associated with higher risk of prevalent and incident dementia, but not with a more rapid rate of cognitive decline. The independent effect of illiteracy on dementia risk may be through a lower range of cognitive function, which is closer to diagnostic thresholds for dementia than the range of literate participants.

Growth hormone locus expands and diverges after the separation of New and Old World Monkeys.

While most mammals including the prosimians have a single copy of the growth hormone (GH) gene, anthropoids possess a cluster of GH-related genes. Throughout the evolution of the main anthropoid groups [New World Monkeys (NWM), Old World Monkeys (OWM), and apes], two features stand out of the GH loci. The first is the appearance of chorionic somatommamotropin hormone (CSH) genes within the OWM lineage and the second is the expansion of the loci intergenic regions in the OWM and apes. In relation with this loci expansion, the NWM possess intergenic regions of homogeneous lengths (3.5 kb). In contrast, heterogeneous lengths (6 and 13 kb) have been reported for species of the OWM. At the present, none of the OWM genomic GH loci organizations have been described. Here, we report the genomic organization of the GH locus in the rhesus monkey, this locus has six GH-related genes separated by five intergenic regions. The 5' end gene (GH-1) encodes for the pituitary GH and is followed by CSH-1, GH-2, CSH-2, CSH-3 and CSH-4 genes. The five intergenic regions have heterogeneous lengths and also present more or less the same Alu distribution as the human GH locus. To analyze the events that contributed to the extension of the intergenic regions of the GH locus and the emergence of the regulatory elements, the five GH locus intergenic regions of the spider monkey (NWM) were sequenced. The results of comparing the loci from both species suggest that the long intergenic regions (13 kb) of the rhesus GH locus share a common ancestor with the 3.5 kb intergenic regions of the spider monkey. However, the observed increased length of the former is due to an insertion (approximately 8.7 kb) at their 3' end. Interestingly in this insert, we discovered a DNA element resembling the enhancer of the CSH genes of the human GH locus. On the other hand, we observed that the short intergenic regions (6 kb) increased by a different recombination event.