Background Although being employed during midlife is positively associated with cognitive function in later life, little is known with respect to cumulative trajectories or durations of time spent in different kinds of work.
Methods We investigated the relationships between employment trajectory from ages 31 years to 50 years and cognitive skills at ages 50–78 years among 2521 adults in the US Panel Study of Income Dynamics from 1968 to 2016. Sequence analysis was used to identify prototypical employment trajectories, capturing employment status and high versus lower job skill level at each year of age from 31 years to 50 years. Adjusted and weighted logistic regression was used to estimate relationships between employment trajectory and performance on each of four cognitive tests representing numerical reasoning, verbal reasoning, health literacy and financial literacy. Dose–response relationships between the duration of high-skill employment and cognitive skills were examined.
Results Seven prototypical employment trajectories were identified, the most common being consistently lower skill employment (44%; 1105/2521). Consistently high-skill and fluctuating skill trajectories were associated with high numerical reasoning scores (OR=1.54, 95% CI 0.99 to 2.40; OR=2.52, 95% CI 1.39 to 4.58, respectively), compared with consistently lower skill employment. There was a dose–response relationship between duration of high-skill employment and numerical reasoning (OR=1.17; 95% CI 1.06 to 1.28), plateauing after approximately 4 years of high-skill employment.
Conclusions Sequence analysis of exposure trajectories is a novel method for life course epidemiology that accounts for exposure timing, duration and ordering. Our results using this method indicate that the duration may be more important than the timing of high-skill midlife employment for later-life numerical reasoning skills.
- life course epidemiology
- longitudinal studies
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Contributors LCK: study concept, study design, acquisition of the data, statistical analysis, interpretation of the data, wrote the first draft of the manuscript, critical revision of the manuscript for important intellectual content and final approval of the manuscript for publication. JMF: statistical analysis, interpretation of the data, critical revision of the manuscript for important intellectual content and final approval of the manuscript for publication. Both authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Funding The US Panel Study of Income Dynamics is supported by the National Institutes of Health (R01 HC069609; R01 AG040213; P01 AG029409) and the National Science Foundation (SES 1157698; 1623684). This work was funded by a grant from the National Institute on Aging of the National Institutes of Health (P01 AG029409).
Competing interests None declared.
Patient consent Not required.
Ethics approval Ethical approval was granted and is reviewed annually by the University of Michigan Health Sciences and Behavioral Sciences Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The US Panel Study of Income Dynamics is a publicly available data source operated by the University of Michigan: https://psidonline.isr.umich.edu/.