Contribution of IQ in young adulthood to the associations of education and occupation with cognitive ability in older age
Open Access
- 5 June 2021
- journal article
- research article
- Published by Springer Science and Business Media LLC in BMC Geriatrics
- Vol. 21 (1), 1-10
- https://doi.org/10.1186/s12877-021-02290-y
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 eta20.076;p < 0.001) and occupation (partial eta2 = 0.037; p < 0.001) were each significantly associated withg. For education, the association was attenuated but remained statistically significant when pre-morbid IQ was controlled for (partial eta20.036;p < 0.001) and was unchanged with additional adjustment for depression (partial eta20.037;p < 0.001). For occupation, the association withgwas 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 withg(partial eta20.030;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.Funding Information
- Seventh Framework Programme (HEALTH-F2–2014–60246)
- Max-Delbrück-Centrum für Molekulare Medizin in der Helmholtz-Gemeinschaft (MDC)
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