Childhood affluence was associated with faster rate of cognitive decline late in life in a longitudinal European study.
Despite having higher levels of fluid intelligence in old age, people who grew up in the most advantaged circumstances experienced a decline in verbal fluency almost 1.6 times faster than people raised in the most disadvantaged circumstances, according to Marja Aartsen, PhD, of Oslo Metropolitan University in Norway, and colleagues.
Faster cognitive decline for people with advantaged childhoods was less pronounced after controlling for adulthood socioeconomic conditions and current levels of physical activity, depressive symptoms, and partner status, the team wrote in Proceedings of the National Academy of Sciences.
“Although counterintuitive at first sight, it fits to theories about cognitive reserve,” Aartsen told MedPage Today. “People with an advantaged childhood develop larger brain reserves throughout their life, which helps to repair neuronal losses in later life and postpones cognitive decline until the underlying cognitive pathology is substantial and speed of decline accelerated.”
A number of studies have shown links between childhood conditions and cognitive change in later life, with mixed results. “We reasoned that part of the inconsistencies in study findings might stem from differences in the analytical approach, or too little change because of a short follow-up, too young people, or too small sample — all causing too little power to find significant effects — or differences in the measurement of the childhood conditions,” Aartsen explained.
“However, contrary to our expectations, we found that more advantaged childhood conditions was related to a stronger decline in later life,” she continued. “We did a number of robustness checks to double-check our findings, but they did not lead to different conclusions.”
The study was based on six waves of the Survey of Health, Aging, and Retirement in Europe (SHARE). Researchers looked at 24,066 people at baseline who were ages 50 to 96 years; 56% of the sample was female and people suspected to have dementia at baseline were excluded. Data were collected at baseline (2004) and every 2 years after that. Childhood socioeconomic status was based on four indicators at age 10: the main breadwinner’s occupational position, the number of books at home, overcrowding, and housing quality.
The researchers examined trajectories of two cognitive functions, delayed recall (assessed by a 10-word delayed recall test) and verbal fluency (assessed by an animal naming test). Over the study period, the average number of observations for each participant was 2.76 for delayed recall and 3.29 for verbal fluency.
Overall, the more advantaged the childhood environment was, the higher the levels of delayed recall and verbal fluency were in later life.
Cognitive decline was related to childhood affluence only for verbal fluency, not for delayed recall: people with a more advantaged childhood experienced more decline in verbal fluency than people with the most disadvantaged childhood socioeconomic conditions. Associations between childhood environment and level of functioning were partly mediated by socioeconomic conditions throughout the life course, but not by current levels of physical activity, depressive symptoms, or having a partner.
One reason for this unexpected finding may lie in the study’s power to find significant results, the authors said; the study sample was at least two times bigger than those of other studies.
But at least two other explanations are possible, suggested Jeffrey Burr, PhD, of the McCormack Graduate School of Policy and Global Studies at the University of Massachusetts in Boston, who was not involved with the study.
First, selective survival may be in play. “Persons who grew up in the most disadvantaged group and who had comparatively lower cognitive reserve may have been more likely to die compared to persons with more advantaged childhoods prior to the observation period of the SHARE data, leaving behind a more cognitively robust group of older adults with poor childhoods,” he told MedPage Today.
Second, it’s possible people with the lowest cognitive abilities may not have been able to participate in SHARE. “These people may have had poorer childhoods and were thus disproportionately less likely to be part of the SHARE study than persons who grew up in more advantaged circumstances,” Burr pointed out.
“More research needs to be done on this topic generally, and specifically, researchers need to continue to seek out and employ designs that reduce the possibility of selection effects,” he added.
The study had other limitations, the authors noted. Participants self-reported socioeconomic circumstances, and responses were subject to recall bias and social desirability. Genes also may be an important factor and a potentially confounding influence, they added, and other variables may have played a role.
The research was supported by the Swiss National Centre of Competence in Research LIVES–Overcoming Vulnerability: Life Course Perspectives, which is financed by the Swiss National Science Foundation; Aartsen reported support from the Research Council of Norway and Nordforsk; and a co-author reported support from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement.
The researchers reported having no conflicts of interest.