To what extent does IQ 'explain' socio-economic variations in function?

The impact of poverty and socioeconomic status on brain, behaviour, and development: a unified framework

In this article, we, for the first time, provide a comprehensive overview and unified framework of the impact of poverty and low socioeconomic status (SES) on the brain and behaviour. While there are many studies on the impact of low SES on the brain (including cortex, hippocampus, amygdala, and even neurotransmitters) and behaviours (including educational attainment, language development, development of psychopathological disorders), prior studies did not integrate behavioural, educational, and neural findings in one framework. Here, we argue that the impact of poverty and low SES on the brain and behaviour are interrelated. Specifically, based on prior studies, due to a lack of resources, poverty and low SES are associated with poor nutrition, high levels of stress in caregivers and their children, and exposure to socio-environmental hazards. These psychological and physical injuries impact the normal development of several brain areas and neurotransmitters. Impaired functioning of the amygdala can lead to the development of psychopathological disorders, while impaired hippocampus and cortex functions are associated with a delay in learning and language development as well as poor academic performance. This in turn perpetuates poverty in children, leading to a vicious cycle of poverty and psychological/physical impairments. In addition to providing economic aid to economically disadvantaged families, interventions should aim to tackle neural abnormalities caused by poverty and low SES in early childhood. Importantly, acknowledging brain abnormalities due to poverty in early childhood can help increase economic equity. In the current study, we provide a comprehensive list of future studies to help understand the impact of poverty on the brain.

Cognitive Function Changes in Older People. Results of Second Wave of Cognition of Older People, Education, Recreational Activities, NutritIon, Comorbidities, fUnctional Capacity Studies (COPERNICUS)

Background

Cognitive reserve explains why subjects with more years of education, professional achievement, or participation in recreational activities show less cognitive decline with aging. We hypothesize that levels of recreational travel, education, occupation, systemic health, physical performance, and current cognitive activity levels affect the trajectory of cognitive function in older, healthy people in Poland.

Materials and Methods

Healthy, older people (N = 205) were examined and followed-up at 2 years. Participants completed physical and cognitive function assessments: including the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA) and its two subtests Delayed Recall (DR) and Verbal Fluency (VF), and Trail Making Test Part B (TMT B). Factors associated with cognitive functioning were also examined.

Results

The MMSE result significantly decreased over 2 years. No significant decrease in other cognitive tests was noted. However, the trajectory of cognitive tests results varied between individual participants. Percentage of variance of change was explained by the following predictors: 21 in MMSE, 24 in MoCA, 8 in DR, 25 in VF, and 24 in TMT B. Age and the presence of varicose veins were significantly linked to negative changes in MMSE and MoCA scores, while working in a professional occupational status associated with a higher score. The subgroup with varicose veins did worse on the Delayed Recall subtest of MoCA.

Conclusion

Cognitive reserve could be extended by proxies of reserve that are related to systemic health and travel activity. The latter is a combination of social, physical, and cognitive activity and potentially might serve as an intervention to improve cognitive function in older people. However, due to the limitations of this study, results should be interpreted with caution and needs to be replicated in the further studies.

Adolescent socioeconomic status and depressive symptoms in later life: Evidence from structural equation models

BACKGROUND

The complex association between socioeconomic status (SES) and depressive symptoms is not entirely understood and the existing literature does not address the relationship between early-life SES and later-life depression from a life-course perspective, incorporating mediating events.

METHODS

Using data from the Wisconsin Longitudinal Study, we employed structural equation modeling to examine how SES measured at age 18 affects depressive symptoms at age 54 directly and through mediating variables college graduation, marriage, and household income level at age 36.

RESULTS

The total effect of adolescent SES on later-life depressive symptoms is largely mediated through college graduation. Our final model was driven by the effects of women. The variables contributing most to depressive symptoms in women were the direct effect of being raised in a home with a low SES and the indirect effect of low adolescent SES mediated through non-completion of college.

LIMITATIONS

Cohort was exclusively comprised of white, high school graduates born in 1939 (± 2 years). In our analysis we assume that missing values are missing at random (MAR); however, attrition both from death (excluded from our population) and from non-response could be associated with depression, i.e. missing not at random (MNAR).

CONCLUSIONS

This study demonstrates the impact of completion of college, particularly among women, and supports the social mobility hypothesis to explain the relationship between adolescent socioeconomic circumstances and late-life health.

An International Evaluation of Cognitive Reserve and Memory Changes in Early Old Age in 10 European Countries

BACKGROUND

Cognitive reserve was postulated to explain individual differences in susceptibility to ageing, offering apparent protection to those with higher education. We investigated the association between education and change in memory in early old age.

METHODS

Immediate and delayed memory scores from over 10,000 individuals aged 65 years and older, from 10 countries of the Survey of Health, Ageing and Retirement in Europe, were modeled as a function of time in the study over an 8-year period, fitting independent latent growth models. Education was used as a marker of cognitive reserve and evaluated in association with memory performance and rate of change, while accounting for income, general health, smoking, body mass index, gender, and baseline age.

RESULTS

In most countries, more educated individuals performed better on both memory tests at baseline, compared to those less educated. However, education was not protective against faster decline, except for in Spain for both immediate and delayed recall (0.007 [SE = 0.003] and 0.006 [SE = 0.002]), and Switzerland for immediate recall (0.006 [SE = 0.003]). Interestingly, highly educated Italian respondents had slightly faster declines in immediate recall (-0.006 [SE = 0.003]).

CONCLUSIONS

We found weak evidence of a protective effect of education on memory change in most European samples, although there was a positive association with memory performance at individuals' baseline assessment.

Association Between Low IQ Scores and Early Mortality in Men and Women: Evidence From a Population-Based Cohort Study

Lower (versus higher) IQ scores have been shown to increase the risk of early mortality, however, the underlying mechanisms are poorly understood and previous studies underrepresent individuals with intellectual disability (ID) and women. This study followed one third of all senior-year students (approximately aged 17) attending public high school in Wisconsin, U.S. in 1957 (n  =  10,317) until 2011. Men and women with the lowest IQ test scores (i.e., IQ scores ≤ 85) had increased rates of mortality compared to people with the highest IQ test scores, particularly for cardiovascular disease. Importantly, when educational attainment was held constant, people with lower IQ test scores did not have higher mortality by age 70 than people with higher IQ test scores. Individuals with lower IQ test scores likely experience multiple disadvantages throughout life that contribute to increased risk of early mortality.

A 35-year longitudinal assessment of cognition and midlife depression symptoms: the Vietnam Era Twin Study of Aging

OBJECTIVE

To determine whether early adult cognitive ability is a risk factor for depressive symptoms in midlife and how genetic and environmental influences explain the association and to examine cross-sectional relationships between depressive symptoms and specific cognitive abilities at midlife.

DESIGN

A 35-year longitudinal and cross-sectional twin study of cognitive aging.

SETTING

Large multicenter study in the United States.

PARTICIPANTS

One thousand two hundred thirty-seven male twins aged 51 to 60 years.

MEASUREMENTS

At the age of 20 years and midlife, participants completed the same version of a general cognitive ability test (Armed Forces Qualification Test [AFQT]). Midlife testing included an extensive neurocognitive protocol assessing processing speed, verbal memory, visual-spatial memory, working memory, executive function, and visual-spatial ability. Participants completed the Center for Epidemiologic Studies Depression Scale before cognitive testing and provided health and life style information during a medical history interview.

RESULTS

Lower age 20 AFQT scores predicted higher levels of depressive symptoms at age 55 years (r = -0.16,p <0.001). In bivariate twin modeling, 77% of the correlation between early cognitive ability and midlife depressive symptoms was due to shared genetic influences. Controlling for current age, age 20 AFQT, and nonindependence ofobservations, depressive symptoms were associated with worse midlife AFQT scores and poorer performance in all cognitive domains except verbal memory.

CONCLUSION

Results suggest that low cognitive ability is a risk factor for depressive symptoms; this association is partly due to shared genetic influences. Crosssectional analyses indicate that the association between depressive symptoms and performance is not linked to specific cognitive domains.

The association of cognitive performance with mental health and physical functioning strengthens with age: the Whitehall II cohort study

BACKGROUND

Cognitive performance has been associated with mental and physical health, but it is unknown whether the strength of these associations changes with ageing and with age-related social transitions, such as retirement. We examined whether cognitive performance predicted mental and physical health from midlife to early old age.

METHOD

Participants were 5414 men and 2278 women from the Whitehall II cohort study followed for 15 years between 1991 and 2006. The age range included over the follow-up was from 40 to 75 years. Mental health and physical functioning were measured six times using SF-36 subscales. Cognitive performance was assessed three times using five cognitive tests assessing verbal and numerical reasoning, verbal memory, and phonemic and semantic fluency. Socio-economic status (SES) and retirement were included as covariates.

RESULTS

High cognitive performance was associated with better mental health and physical functioning. Mental health differences associated with cognitive performance widened with age from 39 to 76 years of age, whereas physical functioning differences widened only between 39 and 60 years and not after 60 years of age. SES explained part of the widening differences in mental health and physical functioning before age 60. Cognitive performance was more strongly associated with mental health in retired than non-retired participants, which contributed to the widening differences after 60 years of age.

CONCLUSIONS

The strength of cognitive performance in predicting mental and physical health may increase from midlife to early old age, and these changes may be related to SES and age-related transitions, such as retirement.

Mental health problems of Dutch adolescents: the association with adolescents' and their parents' educational level

BACKGROUND

We studied the hypothesis of socioeconomic equalization regarding adolescents' mental health problems by examining whether a low educational level of adolescents and their parents shows independent (cumulative) or dependent (including interactive) associations with adolescents' mental health problems, or whether equalization occurred.

METHODS

Cross-sectional data were obtained from the preventive Youth Health Care Centre in a relatively deprived Dutch former mining area. Participants were 1861 adolescents aged 13 or 14 years (response rate 71.7%). The self-administered Dutch version of the Strengths and Difficulties Questionnaire (SDQ) was used to identify adolescents' mental health problems. Multiple logistic regression analyses were used to examine the associations, and linear regression models to check the robustness of the findings.

RESULTS

A low educational level of adolescents was strongly related to their mental health problems (OR = 5.37; 95% CI: 3.31-8.70). The initially high odds ratios for adolescents with low-educated parents (OR = 1.72; 95% CI: 1.14-2.59) disappeared after controlling for the adolescents' own educational level (OR = 1.12; 95% CI: 0.73-1.74). In terms of interactions, no specifically increased odds were found, e.g. for low-educated adolescents with high-educated parents.

CONCLUSION

There was no evidence for socioeconomic equalization regarding adolescents' mental health problems. Lower educated adolescents had substantially higher odds of having mental health problems, regardless of their parents' education. The odds may be affected by differences in intelligence and life events. Youth healthcare workers should collaborate closely with schools to intervene in time, particularly among low-educated adolescents. More interventions are probably needed to reduce these major inequities.