In a recent study published in the journal Scientific Reports, researchers examined the role of different adversities experienced at different life course stages on cognitive aging (i.e., level and change).
Study: Adversity specificity and life period exposure on cognitive aging. Image Credit: myboys.me / Shutterstock
Background
Previous studies have reported on the effects of stress during various life stages on the frontal lobes, amygdala, and hippocampus, which are involved in memory, learning, and functions associated with higher cognition. Associations between socioeconomic adversity during adulthood and cognition have also been documented.
Adversity impacts cognition in aging, affecting both specific and cumulative experiences. Unfortunately, existing data on adversity's effects on cognitive performance and change among older individuals is contradictory, requiring a comprehensive model to understand the impact of different adversities experienced at different life course stages on cognitive function and performance.
About the study
In the present study, researchers investigated the role of distinct adversities (loss of parents, stress, hunger, and economic hardship) experienced at three life course periods (early life, early adult age, and middle age) in predicting cognitive performance at an older age and the change in cognitive performance across the aging process (level and change in cognition).
The Survey of Health, Ageing, and Retirement in Europe (SHARE) study data of 2,662 individuals aged >60.0 years (median age of 68 years), were analyzed using structural equation modeling. The team investigated whether, at each life course period, adversity was related to lower verbal fluency (VF) performance and memory in older age and a steeper decline in VF and memory.
Only individuals having complete cognition-associated data for all follow-ups (SHARE study waves 1.0, 2.0, 4.0, 5.0, 6.0, and 7.0), who were not suspected of suffering from dementia during the first and second waves of the study (excluding individuals with scores below 2.0 concerning temporal orientation), and those who participated who filled out the retrospective SHARELIFE questionnaire during the third or seventh wave were included in the present analysis.
The study commenced in 2004 and was conducted every two years until 2017-2018. Cognitive improvements were observed during the first and second waves, probably because of learning effects, but showed declining trends subsequently. Therefore, data from only the second, fourth, fifth, sixth, and seventh waves were analyzed to assess changes in cognition with time.
The team assessed delayed-type recall by making the participants recall ten words that were spoken loudly during the study waves, followed by time delays during which the VF and numeracy tasks were completed. Participants had to name different animals within a minute in the VF task. Adversities were evaluated by matching various items with the adversity definitions (i.e., periods of hunger, stress, economic hardship, and the death of one or both parents) throughout the life course.
For each item, the participants documented the calendar year of event commencement, and based on the difference in the birth dates, the team determined the period of life during which the adversity was experienced. The course of life was divided into early life (0.0 to 20.0 years of age), early adulthood (21.0 to 40.0 years of age), and middle age (41.0 to 60.0 years of age).
Results
The early experience of economic hardship predicted lower VF performance, and the experience of hunger in early life predicted lower delayed recall and lower VF performance. However, adversities experienced later in life (in early and middle adulthood) did not negatively predict cognition and associated changes in older age. Contrastingly, stress and economic hardship experienced in early adulthood predicted delayed recall and VF performance better in older age. In contrast, economic difficulties experienced in middle adulthood predicted a lower decline in delayed recall.
Older individuals, less educated males, and those with less educated fathers had worse delayed recall performance in older age. VF performance was worse among elders with less educated parents and those participants who were less educated. Older individuals also declined more steeply in delayed recall performance across waves. Middle-age economic hardship reduces delayed recall, enhances cognitive performance, and encourages paid work, while adulthood provides better resources and creativity.
Conclusions
Overall, the study findings showed that adversity experienced in early life (particularly hunger and economic hardship) was negatively associated with cognitive aging, which was not the case with adversity experienced later in life. The findings highlighted the importance of the sensitive period (early life) in the experience of adversity and the adverse effects of economic hardship and hunger early in life on later life cognitive health, which could inform social policy-making.
Early life adversity, hunger, and disadvantageous socioeconomic conditions could have long-lasting impacts on cognition in older age compared to adulthood. Economic hardship experienced in early life seemed to influence the level of VF performance and the change in delayed recall, probably due to fewer mental stimulations and a worse lifestyle due to economic constraints during early life, resulting in a lower cognitive build-up. Hunger in early life may cause alterations in neurotransmitter systems that impact cognition.
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