Childhood Poverty Linked to Lower Cognitive Performance Later in Life

Damian McNamara

October 04, 2018

Lower socioeconomic status in childhood is associated with worse cognitive performance in adulthood, new research suggests.

Among more than 20,000 older adult participants in the prospective Survey of Health, Aging and Retirement in Europe (SHARE) cohort study, those with socioeconomic hardship at the age of 10 years scored lower on all cognitive tests administered than those who did not experience this type of hardship.

"Our study suggests that people that grew up in a less resourceful environment reach a lower level of cognitive performance," principal investigator Pavla Cermakova, MD, PhD, National Institute of Mental Health in Klecany, Czech Republic, told Medscape Medical News.

However, childhood socioeconomic hardship was not significantly linked to rate of cognitive decline associated with aging.

In terms of possible solutions, education was the strongest potentially modifiable clinical and social risk factor.

"The risks that come from a lower socioeconomic position in childhood could be thus mitigated by providing equal educational opportunities to children that have a disadvantage from earlier life," Cermakova said.

The findings were published online September 26 in Neurology.

Growing Evidence

The current study adds to a growing body of evidence suggesting that cognitive aging is a lifelong process that may have its roots in a disadvantaged childhood socioeconomic position, the researchers note.

They assessed participants from six waves of the ongoing SHARE study. SHARE assesses community-dwelling Europeans approximately every 2 years with regard to their health, social networks, and economic conditions. The SHARE waves included in the current study were conducted from 2004 to 2015.

The median age of the current analyses' 20,244 participants at baseline was 71 years, and 54% were women.

With each wave of data collection, with the exception of wave 3, SHARE investigators measured verbal learning, delayed recall gained from an adapted 10-word delay recall test, and verbal fluency from an animal word fluency test. They also calculated a cognition global score by converting each of these measures into a z score.

The number of people in the household at age 10 years, divided by the number of rooms, as well as the number of books in the house were among the indirect measures of socioeconomic position (SEP).

Results showed that 844 participants (about 4%) experienced socioeconomic hardship in childhood.

Lower Test Scores

Participants who experienced childhood socioeconomic hardship scored lower on all cognitive tests than those without such hardship (mean, -0.35 ± SD 0.76 vs 0.02 ± SD 0.82 for global cognition; P < .001).

Similarly, after adjusting for age, sex, and country of origin, childhood socioeconomic hardship was associated with lower cognitive scores (β = -0.274; 95% confidence interval [CI], -0.323 to -0.225 for global cognition).

In secondary analyses, overcrowding in childhood was associated with a lower level of baseline global cognition after adjusting for age, sex, and country of origin (β = -0.04; 95% CI, -0.05 to -0.04).

The investigators also accounted for multiple covariates, including body mass index, EURO-D scale depressive symptoms, cardiovascular disease, smoking, drinking more than two glasses of alcohol almost every day, physical inactivity, having a partner in the household, and current employment.

After adjusting for all clinical and social risk factors, the association between socioeconomic hardship and global cognition score was attenuated by approximately 45% but remained statistically significant (β = -0.150; 95% CI, -0.196 to -0.103 for global cognition). This finding was similar across all cognitive tests.

Overall, country of origin and education explained most of the variance (at 12% and 9%, respectively). When assessed separately, education was most protective, reducing the association between lower childhood SEP and later cognition by 35%. Depression reduced the link by 12%, but the remaining factors had only small effects.

"Considering the present findings, adverse household conditions could be an appropriate indicator for identifying at-risk children who would benefit in the long term from targeted educational interventions," the researchers note.

Clinical Implications

The association between SEP in childhood and later cognitive performance might be explained by the "passive cognitive reserve" concept, Cermakova said. In this framework, the socioeconomic environment where people grow up shapes the development of the brain and determines which cognitive level people reach.

"On the contrary, our study does not suggest that childhood socioeconomic conditions influence how the aged brain fights against the decline in cognitive functions while we age," she added.

All the findings taken together suggest that interventions aimed at improving cognitive aging should also target socioeconomic hardship in childhood, the researchers note.

The current study included more participants than previous studies. In addition, people from 16 different countries, including those in Central and Eastern Europe, were included. The longitudinal design of the study is another strength, the investigators add.

However, asking participants to recall childhood conditions could introduce recall bias, a potential limitation, they write. In addition, the SHARE dataset does not include risk factors such as blood pressure, cholesterol, social and maternal deprivation, or loneliness. Possible survivor bias is another possible limitation; children who experience socioeconomic hardship face a higher risk for death than others do.

Cermakova and colleagues are now calling for future studies with more risk factors and longer follow-up to see whether their findings are replicated. "We should understand more the complex social and biological mechanisms, which could explain the observed association," she said.

Unsupported Conclusions?

Asked to comment on the findings, Michael L. Goldstein, MD, a child neurologist in Tiburon, California, a fellow of the American Academy of Neurology (AAN), and past chair of the Child Neurology Section for the AAN, told Medscape Medical News that the study draws two conclusions from the data collected.

"First, children who were economically disadvantaged are also intellectually disadvantaged as older adults. Second, age-associated intellectual decline affects both groups equally," said Goldstein, who was not involved with the research.

However, "the data did not address how economically disadvantaged children might avoid becoming intellectually disadvantaged older adults, so their conclusions about interventions, while well intentioned and possibly correct, are not supported by their data," he added.

"It is difficult for a child's physician to know what action to take as a result of this study. It is easy to argue that increasing educational resources for all children is worthwhile," Goldstein said.

"But an argument that advocating for increasing resources for disadvantaged children over others, while possibly appropriate, must be based on data not presented in this paper."

Data collection for the SHARE study was primarily funded by the European Commission, with additional support from the German Ministry of Education and Research, the Max Planck Society for the Advancement of Science, and the US National Institute on Aging. Dr Cermakova and Dr Goldstein have reported no relevant financial relationships.

Neurology. Published online September 26, 2018. Abstract

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