Geoff Der

Effect of breast feeding on intelligence in children: prospective study, sibling pairs analysis, and meta-analysis

Abstract Objective To assess the importance of maternal intelligence, and the effect of controlling for it and other important confounders, in the link between breast feeding and childrens intelligence. Design Examination of the effect of breast feeding on cognitive ability and the impact of a range of potential confounders, in particular maternal IQ, within a national database. Additional analyses compared pairs of siblings from the sample who were and were not breast fed. The results are considered in the context of other studies that have also controlled for parental intelligence via meta-analysis. Setting 1979 US national longitudinal survey of youth. Subjects Data on 5475 children, the offspring of 3161 mothers in the longitudinal survey. Main outcome measure IQ in children measured by Peabody individual achievement test. Results The mothers IQ was more highly predictive of breastfeeding status than were her race, education, age, poverty status, smoking, the home environment, or the childs birth weight or birth order. One standard deviation advantage in maternal IQ more than doubled the odds of breast feeding. Before adjustment, breast feeding was associated with an increase of around 4 points in mental ability. Adjustment for maternal intelligence accounted for most of this effect. When fully adjusted for a range of relevant confounders, the effect was small (0.52) and non-significant (95% confidence interval −0.19 to 1.23). The results of the sibling comparisons and meta-analysis corroborated these findings. Conclusions Breast feeding has little or no effect on intelligence in children. While breast feeding has many advantages for the child and mother, enhancement of the childs intelligence is unlikely to be among them.

Reaction times and intelligence differences: A population-based cohort study

The association between reaction times and psychometric intelligence test scores is a major plank of the information-processing approach to mental ability differences. An important but unavailable datum is the effect size of the correlation in the normal population. Here we describe the associations between scores on a test of general mental ability (Alice Heim 4, AH4) and reaction times using a ‘Hick’-style device. The sample is 900 people aged 56 years who are broadly representative of the Scottish population. AH4 Part I total scores correlated −.31 with simple reaction time, −.49 with four-choice reaction time, and −.26 with intraindividual variability in both reaction time procedures. The correlation between AH4 scores and the difference between simple and four-choice reaction time was −.15. Separate analyses were conducted after partitioning the total group according to sex, educational level, social class grouping, and number of errors on the four-choice reaction time task. None of these factors significantly altered the effect sizes. This is the first report of reaction time and psychometric intelligence in a large, normal sample of the population. It provides a benchmark for other studies and suggests larger effect sizes than the majority of present studies, which are dominated by young student samples.

Incidence and outcome of schizophrenia in Whites, African-Caribbeans and Asians in London

BACKGROUND Several previous studies have indicated high rates of schizophrenia in African-Caribbeans in the UK compared to White population. METHOD All people aged 18 to 64 years residing in two health districts in London who made contact with hospital or community services over a 1-year (Whites) or 2-year (ethnic minorities) period were screened for psychotic symptoms. RESULTS One hundred and twenty-three patients passed the screen, of whom 100 were assigned a schizophrenic class by the CATEGO program. Of these, 38 were White, 38 African-Caribbean and 24 Asian. The incidence rate for broad schizophrenia was significantly higher for African-Caribbeans than for Whites. Asians showed a high rate among people age 30 and over, particularly women. Poor outcome at 1-year follow-up was significantly more common for African-Caribbeans than for the other two groups. The proportion of African-Caribbeans with a poor outcome was two and a half times greater than that of Whites. On a range of seven socio-demographic variables, African-Caribbeans differed from the other two groups only on unemployment. CONCLUSIONS A multitide of factors play a role in the aetiology of schizophrenia. Comparison of environmental factors in these groups may identify factors that contribute to the aetiology of schizophrenia.

Do housing tenure and car access predict health because they are simply markers of income or self esteem? A Scottish study.

OBJECTIVE: To investigate relations between health (using a range of measures) and housing tenure or car access; and to test the hypothesis that observed relations between these asset based measures and health are simply because they are markers for income or self esteem. DESIGN: Analysis of data from second wave of data collection of West of Scotland Twenty-07 study, collected in 1991 by face to face interviews conducted by nurse interviewers. SETTING: The Central Clydeside Conurbation, in the West of Scotland. SUBJECTS: 785 people (354 men, 431 women) in their late 30s, and 718 people (358 men, 359 women) in their late 50s, participants in a longitudinal study. MEASURES: General Health Questionnaire scores, respiratory function, waist/hip ratio, number of longstanding illnesses, number of symptoms in the last month, and systolic blood pressure; household income adjusted for household size and composition; Rosenberg self esteem score; housing tenure and care access. RESULTS: On bivariate analysis, all the health measures were significantly associated with housing tenure, and all except waist/hip ratio with car access; all except waist/hip ratio were related to income, and all except systolic blood pressure were related to self esteem. In models controlling for age, sex, and their interaction, neither waist/hip ratio nor systolic blood pressure remained significantly associated with tenure or care access. Significant relations with all the remaining health measures persisted after further controlling for income or self esteem. CONCLUSIONS: Housing tenure and car access may not only be related to health because they are markers for income or psychological traits; they may also have some directly health promoting or damaging effects. More research is needed to establish mechanisms by which they may influence health, and to determine the policy implications of their association with health.

Peer Victimization and Depression in Early-Mid Adolescence: A Longitudinal Study.

BACKGROUND Despite considerable evidence for psychological distress among children and young people who experience peer victimization, cross-sectional studies cannot determine the direction of the relationship. Several recent studies have examined associations between victimization and distress. The majority find evidence for both directions but do not arbitrate between them; only one prior study has attempted to do this. AIMS To use longitudinal data to: (1) test competing hypotheses about the direction of the victimization-depression association; (2) investigate gender differences in the resulting models. SAMPLE Data were obtained from a Scottish school-based cohort (N=2,586). METHODS Self-completion questionnaires included a depression scale and questions on victimization at each age. RESULTS Despite shifts in and out of victim status, there was evidence of stability in both victimization and depression. Bivariate analyses showed positive relationships between victimization and depression. Structural equation modelling (SEM) showed that at age 13, this relationship was reciprocal, with a stronger path from victimization to depression than vice versa. However, at age 15, it was almost entirely due to a path from depression to victimization among boys. Models including cross-lagged paths fitted the data less well than those including simultaneous associations. CONCLUSIONS Current policy focuses on victimization as a cause of distress; however, professionals should be aware that vulnerable children and young people are likely to be the targets of victimization.

Intelligence in youth and all-cause-mortality: systematic review with meta-analysis

BACKGROUND A number of prospective cohort studies have examined the association between intelligence in childhood or youth and life expectancy in adulthood; however, the effect size of this association is yet to be quantified and previous reviews require updating. METHODS The systematic review included an electronic search of EMBASE, MEDLINE and PSYCHINFO databases. This yielded 16 unrelated studies that met inclusion criteria, comprising 22,453 deaths among 1,107,022 participants. Heterogeneity was assessed, and fixed effects models were applied to the aggregate data. Publication bias was evaluated, and sensitivity analyses were conducted. RESULTS A 1-standard deviation (SD) advantage in cognitive test scores was associated with a 24% (95% confidence interval 23-25) lower risk of death, during a 17- to 69-year follow-up. There was little evidence of publication bias (Eggers intercept = 0.10, P = 0.81), and the intelligence-mortality association was similar for men and women. Adjustment for childhood socio-economic status (SES) in the nine studies containing these data had almost no impact on this relationship, suggesting that this is not a confounder of the intelligence-mortality association. Controlling for adult SES in five studies and for education in six studies attenuated the intelligence-mortality hazard ratios by 34 and 54%, respectively. CONCLUSIONS Future investigations should address the extent to which attenuation of the intelligence-mortality link by adult SES indicators is due to mediation, over-adjustment and/or confounding. The explanation(s) for association between higher early-life intelligence and lower risk of adult mortality require further elucidation.

Depression and disability in Parkinson's disease: a follow-up of 132 cases

Patients with Parkinsons disease, 132 in number, were followed up after approximately one year, and measures of depression and disability re-administered. Depression was common on both occasions, and was characterized by dysphoria, pessimism and somatic symptoms, but not guilt or self-blame. Depression and disability were associated on both occasions. The relationship between changes in disability and depression across time was complex. In trying to understand changes in depression, the absolute change in disability may be less important than the relative change and rate of change. The results were discussed in relation to findings from other disease groups, and the implications for the clinical management of depression in Parkinsons disease.

Neuroticism, extraversion, and mortality in the UK health and lifestyle survey : A 21-year prospective cohort study

Objective: To examine the influence of neuroticism and extraversion on all-cause and cause-specific mortality over 21 years after controlling for risk factors. Methods: Participants were members of the Health and Lifestyle Survey, a British nationwide sample survey of 9003 adults. At baseline (1984 to 1985), individuals completed a sociodemographic and health questionnaire, underwent physical health examination, and completed the Eysenck Personality Inventory. Mortality was assessed for 21 years after baseline. A total of 5424 individuals had complete data. Results: After controlling for age and gender, 1-standard deviation (SD) increase in neuroticism was related to 9% (hazard ratio (HR) = 1.09; 95% Confidence Interval (CI) = 1.03–1.16) increased risk of mortality from all causes. The association was nonsignificant (HR = 1.05; 95% CI = 0.99–1.11) after additionally controlling for occupational social class, education, smoking, alcohol consumption, physical activity, and health. There was 12% (HR = 1.12; 95% CI = 1.03–1.21) increased risk of death from cardiovascular disease associated with 1-SD increase in neuroticism. This was still significant after adjustment. When the sample was divided into 40- to 59-year-olds and those ≥60 years, neuroticism remained a significant risk for all-cause mortality and cardiovascular disease mortality; associations were nonsignificant after controlling for all covariates. Neuroticism was not associated with deaths from stroke, respiratory disease, lung cancer, or other cancers. Extraversion was protective of death from respiratory disease (HR = 0.84; 95% CI = 0.70– 1.00). Conclusions: After controlling for several risk factors, high neuroticism was significantly related to risk of death from cardiovascular disease. The effects of neuroticism on death from cardiovascular disease may be mediated by sociodemographic, health behavior, and physiological factors. EPI = Eysenck Personality Inventory; HR = hazard ratio; CI = Confidence Interval; HALS = Health and Lifestyle Survey; CVD = cardiovascular disease; CHD = coronary heart disease; BMI = body mass index; BP = blood pressure; FEV = forced expiratory volume.

Gender and telomere length: Systematic review and meta-analysis

BACKGROUND It is widely believed that females have longer telomeres than males, although results from studies have been contradictory. METHODS We carried out a systematic review and meta-analyses to test the hypothesis that in humans, females have longer telomeres than males and that this association becomes stronger with increasing age. Searches were conducted in EMBASE and MEDLINE (by November 2009) and additional datasets were obtained from study investigators. Eligible observational studies measured telomeres for both females and males of any age, had a minimum sample size of 100 and included participants not part of a diseased group. We calculated summary estimates using random-effects meta-analyses. Heterogeneity between studies was investigated using sub-group analysis and meta-regression. RESULTS Meta-analyses from 36 cohorts (36,230 participants) showed that on average females had longer telomeres than males (standardised difference in telomere length between females and males 0.090, 95% CI 0.015, 0.166; age-adjusted). There was little evidence that these associations varied by age group (p=1.00) or cell type (p=0.29). However, the size of this difference did vary by measurement methods, with only Southern blot but neither real-time PCR nor Flow-FISH showing a significant difference. This difference was not associated with random measurement error. CONCLUSIONS Telomere length is longer in females than males, although this difference was not universally found in studies that did not use Southern blot methods. Further research on explanations for the methodological differences is required.

Reaction Time Explains IQ's Association with Death

Lower IQ is associated with earlier death, but the cause of the relationship is unknown. In the present study, psychometric intelligence and reaction times were both significantly related to all-cause mortality in a representative sample of 898 people aged 56 years who were followed up with respect to survival until age 70. The association between IQ and mortality remained significant after adjusting for education, occupational social class, and smoking, all of which have been hypothesized as confounding variables. The effect of IQ on mortality was not significant after adjusting for reaction time, suggesting that reduced efficiency of information processing might link lower mental ability and earlier death. This new field of cognitive epidemiology provides arguably the strongest evidence for the importance of psychological factors in physical health and human survival. Finding the mechanisms that relate psychometric intelligence to mortality might help in formulating effective interventions to reduce inequalities in health.