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Contribution of IQ in young adulthood to the associations of education and occupation with cognitive ability in older age

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Item Type:Article
Title:Contribution of IQ in young adulthood to the associations of education and occupation with cognitive ability in older age
Creators Name:Feinkohl, I. and Kozma, P. and Borchers, F. and van Montfort, S.J.T. and Kruppa, J. and Winterer, G. and Spies, C. and Pischon, T.
Abstract:BACKGROUND: Studies suggest that a higher education and occupation are each associated with a higher late-life cognitive ability, but their inter-relationships in their association with cognitive ability and the contribution of peak IQ in young adulthood ('pre-morbid IQ') often remain unclear. METHODS: Cross-sectional analysis of 623 participants aged ≥65 years of the BioCog study. Education was coded according to the International Standard Classification of Education (ISCED; range 1 to 6). Occupation was coded as 'semi/unskilled', 'skilled manual', 'skilled non-manual', 'managerial', 'professional'. A summary score of global ability (‘g’) was constructed from six cognitive tests. Pre-morbid IQ was estimated from vocabulary. The Geriatric Depression Scale assessed symptoms of depression. Age- and sex-adjusted analyses of covariance were performed. RESULTS: Education (partial eta2 0.076; p < 0.001) and occupation (partial eta2 = 0.037; p < 0.001) were each significantly associated with g. For education, the association was attenuated but remained statistically significant when pre-morbid IQ was controlled for (partial eta2 0.036; p < 0.001) and was unchanged with additional adjustment for depression (partial eta2 0.037; p < 0.001). For occupation, the association with g was no longer significant when pre-morbid IQ (partial eta2 = 0.015; p = 0.06) and depression (partial eta2 = 0.011; p = 0.18) were entered as covariates in separate steps. When education and occupation were entered concurrently into the fully adjusted model, only education was independently associated with g (partial eta2 0.030; p < 0.001; occupation, p = 0.93). CONCLUSION: While a higher education and a higher occupation were each associated with a higher late-life cognitive ability, only for education some unique contribution to cognitive ability remained over and above its relationship with pre-morbid IQ, depression, and occupation. Further research is needed to address whether a longer time spent in education may promote late-life cognitive ability.
Keywords:Cognitive Epidemiology, Cognitive Ageing, Education, Occupation, Pre-Morbid IQ
Source:BMC Geriatrics
Publisher:BioMed Central
Page Range:346
Date:5 June 2021
Official Publication:https://doi.org/10.1186/s12877-021-02290-y
PubMed:View item in PubMed

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