Intelligence in youth and health behaviours in middle age

General cognitive ability assessment in the German National Cohort (NAKO) - The block-adaptive number series task

Objectives. Evaluate the block-adaptive number series task of reasoning, as a time-efficient proxy of general cognitive ability in the Level-2 sample of the German National Cohort (NAKO), a population-based mega cohort.Methods. The number series task consisted of two blocks of three items each, administered as part of the touchscreen-based assessment. Based on performance on the first three items, a second block of appropriate difficulty was automatically administered. Scoring of performance was based on the Rasch model. Relations of performance scores to age, sex, education, study centre, language proficiency, and scores on other cognitive tasks were examined.Results. Except for one very difficult item, the data of the remaining 14 items showed sufficient fit to the Rasch model (Infit: 0.89-1.04; Outfit: 0.80-1.08). The resulting performance scores (N = 21,056) had a distribution that was truncated at very high levels of ability. The reliability of the performance estimates was satisfactory. Relations to age, sex, education, and the executive function factor of the other cognitive tasks in the NAKO supported the validity.Conclusions. The number series task provides a valid proxy of general cognitive ability for the Level-2 sample of the NAKO, based on a highly time-efficient assessment procedure.

Multivariate prediction of cognitive performance from the sleep electroencephalogram

Human cognitive performance is a key function whose biological foundations have been partially revealed by genetic and brain imaging studies. The sleep electroencephalogram (EEG) is tightly linked to structural and functional features of the central nervous system and serves as another promising biomarker. We used data from MrOS, a large cohort of older men and cross-validated regularized regression to link sleep EEG features to cognitive performance in cross-sectional analyses. In independent validation samples 2.5-10% of variance in cognitive performance can be accounted for by sleep EEG features, depending on the covariates used. Demographic characteristics account for more covariance between sleep EEG and cognition than health variables, and consequently reduce this association by a greater degree, but even with the strictest covariate sets a statistically significant association is present. Sigma power in NREM and beta power in REM sleep were associated with better cognitive performance, while theta power in REM sleep was associated with worse performance, with no substantial effect of coherence and other sleep EEG metrics. Our findings show that cognitive performance is associated with the sleep EEG (r = 0.283), with the strongest effect ascribed to spindle-frequency activity. This association becomes weaker after adjusting for demographic (r = 0.186) and health variables (r = 0.155), but its resilience to covariate inclusion suggest that it also partially reflects trait-like differences in cognitive ability.

Can Intelligence Affect Alcohol-, Smoking-, and Physical Activity-Related Behaviors? A Mendelian Randomization Study

People with high levels of intelligence are more aware of risk factors, therefore choosing a healthier lifestyle. This assumption seems reasonable, but is it true? Previous studies appear to agree and disagree. To cope with the uncertainty, we designed a mendelian randomization (MR) study to examine the causal effects of genetically proxied intelligence on alcohol-, smoking-, and physical activity (PA)-related behaviors. We obtained genome-wide association study (GWAS) datasets concerning these variables from separate studies or biobanks and used inverse-variance weighted (IVW) or MR-Egger estimator to evaluate the causal effects according to an MR protocol. The MR-Egger intercept test, MR-PRESSO, and funnel plots were employed for horizontal pleiotropy diagnosis. The Steiger test (with reliability test), Cochran's Q test, MR-PRESSO, and leave-one-out method were employed for sensitivity analysis. We found significant or potential effects of intelligence on alcohol dependence (OR = 0.749, p = 0.003), mental and behavioral disorders due to alcohol (OR = 0.814, p = 0.009), smoking (OR = 0.585, p = 0.005), and smoking cessation (OR = 1.334, p = 0.001). Meanwhile, we found significant or potential effects on walking duration (B = -0.066, p < 0.001), walking frequency (B = -0.055, p = 0.031), moderate PA frequency (B = -0.131, p < 0.001), and vigorous PA frequency (B = -0.070, p = 0.001), but all in a negative direction. In conclusion, our findings reinforce some existing knowledge, indicate the complexity of the health impacts of human intelligence, and underline the value of smoking and alcohol prevention in less intelligent populations. Given the existing limitations in this study, particularly the potential reverse causality in some estimations, re-examinations are warranted in future research.

High intelligence is not associated with a greater propensity for mental health disorders

BACKGROUND

Studies reporting that highly intelligent individuals have more mental health disorders often have sampling bias, no or inadequate control groups, or insufficient sample size. We addressed these caveats by examining the difference in the prevalence of mental health disorders between individuals with high and average general intelligence (g-factor) in the UK Biobank.

METHODS

Participants with g-factor scores standardized relative to the same-age UK population, were divided into two groups: a high g-factor group (g-factor 2 SD above the UK mean; N = 16,137) and an average g-factor group (g-factor within 2 SD of the UK mean; N = 236,273). Using self-report questionnaires and medical diagnoses, we examined group differences in the prevalence of 32 phenotypes, including mental health disorders, trauma, allergies, and other traits.

RESULTS

High and average g-factor groups differed across 15/32 phenotypes and did not depend on sex and/or age. Individuals with high g-factors had less general anxiety (odds ratio [OR] = 0.69, 95% CI [0.64;0.74]) and post-traumatic stress disorder (PTSD; OR = 0.67, 95 %CI [0.61;0.74]), were less neurotic (β = -0.12, 95% CI [-0.15;-0.10]), less socially isolated (OR = 0.85, 95% CI [0.80;0.90]), and were less likely to have experienced childhood stressors and abuse, adulthood stressors, or catastrophic trauma (OR = 0.69-0.90). However, they generally had more allergies (e.g., eczema; OR = 1.13-1.33).

CONCLUSIONS

The present study provides robust evidence that highly intelligent individuals do not have more mental health disorders than the average population. High intelligence even appears as a protective factor for general anxiety and PTSD.

Novel behavioral model in evaluating initiation and sustenance of teeth brushing behavior among students pursuing health sciences: a cross-sectional study

Background: Oral hygiene maintenance is a crucial and integral feature in determining the overall wellbeing of a person. It has been established that interventions for health promotion at the public health level derived from theoretical models based on social and behavioural sciences have a superior effectiveness as compared to the ones without a theoretical background. Hence a novel behavioral model known as the multi-theory model (MTM) was used to understand two important aspects of health behavior change: (i) Initiation and (ii) Sustenance in twice daily teeth brushing in a university setting with objectives to identify factors effecting MTM in initiation and sustenance of twice daily brushing behavior among students pursuing health sciences and correlating the MTM theory with socio-demographic and behavioral patterns.

Methods: The study is an analytical cross-sectional study. Students pursuing Medicine and Dentistry in a University setting were included. A validated questionnaire was designed for this study. Questions were framed to evaluate the constructs of initiation and sustenance of MTM, personality, sleeping habits and demographic corelates of participants. Multiple means between the groups were compared using analysis of variance and a post hoc test. Correlation was established between different domains, the items were then entered for hierarchical multiple regression.

Results: Of the 235 participants in the study, 229 completed the questionnaire. There was a significant association between brushing quartiles, professional streams (p<0.001) and academic performance (p<0.001). The hierarchical multiple regression revealed that at stage one, behavioral confidence contributed significantly to the regression model (F (1,227) = 33.227, p<0.001) and accounted for 12.4% of the variation in twice daily brushing.

Conclusion: MTM is a good tool in predicting the initiation and sustenance of twice daily brushing behavior among young adults and can form a useful tool in assessing the patterns of brushing behavior in a population.

IQ in Adolescence and Cognition over 50 years later: The Mediating Role of Adult Personality

There is substantial evidence for the association between higher early life IQ and better cognition in late life. To advance knowledge on potential pathways, the present study tested whether Five-Factor Model personality traits in adulthood mediate the association between adolescent IQ and later-life cognition. Participants were from the Graduate sample of the Wisconsin Longitudinal Study on Aging (WLS; N= 3,585). IQ was assessed in 1957 (about age 17), personality was assessed in 2003-2005 (age = 64), and cognition was assessed in 2011 (age = 71). Controlling for demographic factors, higher IQ in adolescence was related to higher openness, lower neuroticism, lower extraversion, lower agreeableness and lower conscientiousness in adulthood. Higher openness partially mediated the association between higher IQ and better cognition. Additional analyses indicated that the pattern of associations between IQ, personality and cognition was similar when the polygenic score for cognition was included as an additional covariate. Although effect size were small, this study provides new evidence that openness in adulthood is on the pathway between early life IQ and later-life cognition.

Association of functional health literacy and cognitive ability with self-reported diabetes in the English Longitudinal Study of Ageing: a prospective cohort study

OBJECTIVES

We investigated whether functional health literacy and cognitive ability were associated with self-reported diabetes.

DESIGN

Prospective cohort study.

SETTING

Data were from waves 2 (2004-2005) to 7 (2014-2015) of the English Longitudinal Study of Ageing (ELSA), a cohort study designed to be representative of adults aged 50 years and older living in England.

PARTICIPANTS

8669 ELSA participants (mean age=66.7, SD=9.7) who completed a brief functional health literacy test assessing health-related reading comprehension, and 4 cognitive tests assessing declarative memory, processing speed and executive function at wave 2.

PRIMARY OUTCOME MEASURE

Self-reported doctor diagnosis of diabetes.

RESULTS

Logistic regression was used to examine cross-sectional (wave 2) associations of functional health literacy and cognitive ability with diabetes status. Adequate (compared with limited) functional health literacy (OR 0.71, 95% CI 0.61 to 0.84) and higher cognitive ability (OR per 1 SD=0.73, 95% CI 0.67 to 0.80) were associated with lower odds of self-reporting diabetes at wave 2. Cox regression was used to test the associations of functional health literacy and cognitive ability measured at wave 2 with self-reporting diabetes over a median of 9.5 years follow-up (n=6961). Adequate functional health literacy (HR 0.64; 95% CI 0.53 to 0.77) and higher cognitive ability (HR 0.77, 95% CI 0.69 to 0.85) at wave 2 were associated with lower risk of self-reporting diabetes during follow-up. When both functional health literacy and cognitive ability were added to the same model, these associations were slightly attenuated. Additionally adjusting for health behaviours and body mass index fully attenuated cross-sectional associations between functional health literacy and cognitive ability with diabetes status, and partly attenuated associations between functional health literacy and cognitive ability with self-reporting diabetes during follow-up.

CONCLUSIONS

Adequate functional health literacy and better cognitive ability were independently associated with lower likelihood of reporting diabetes.

Do Physical Activity, BMI, and Wellbeing Affect Logical Thinking?

We studied 6368 people (4544 women and 1824 men; aged 18–74 years). The research goal was to determine whether the Cognitive Reflection Test score (logical thinking compared with intuitive thinking) depends—and in what way it depends—on the healthy lifestyle components and emotional health-related components as well as age (18–74 years) and gender. We established that analytical vs. intuitive thinking depended on components of a healthy lifestyle, physical activity, sleep, eating habits, smoking and alcohol consumption, specificity of sporting activity, body mass index, and emotional health-related components (stress, depression, impulsivity, subjective health, emotional intelligence), as well as age and gender. We found that logical thinking was not associated with sleep, moderate-to-vigorous PA, impulsivity, subjective health, and components of a healthy lifestyle. However, logical thinking decreases with age, gender (higher in men than in women), BMI (decreases in both genders over the second degree of obesity), depression (the more severe depression in women, the worse their logical thinking), sedentary behavior (people who sat for longer periods had more difficulty solving problems), and in professional sportswomen (logical thinking is worse in professional sportswomen than in sedentary women, amateur sportswomen, or women who use gyms). Finally, we determined inverse correlations between logical thinking, emotional intelligence, and stress.

Subjective Socioeconomic Status, Cognitive Abilities, and Personal Control: Associations With Health Behaviours

Objective

To examine subjective and objective socioeconomic status (SSES and OSES, respectively) as predictors, cognitive abilities as confounders, and personal control perceptions as mediators of health behaviours.

Design

A cross-sectional study including 197 participants aged 30–50 years, recruited from the crowd-working platform, Prolific.

Main Outcome Measure

The Good Health Practices Scale, a 16-item inventory of health behaviours.

Results

SSES was the most important predictor of health behaviours (beta = 0.19, p &lt; 0.01). Among the OSES indicators, education (beta = 0.16, p &lt; 0.05), but not income, predicted health behaviours. Intelligence (r = −0.16, p &lt; 0.05) and memory (r = −0.22, p &lt; 0.01) were negatively correlated with health-promoting behaviours, and the effect of memory was upheld in the multivariate model (beta = −0.17, p &lt; 0.05). Personal control perceptions (mastery and constraints) did not act as mediators.

Conclusion

SSES predicted health behaviours beyond OSES. The effect of socioeconomic indicators was not confounded by cognitive abilities. Surprisingly, cognitive abilities were negatively associated with health-promoting behaviours. Future research should emphasise SSES as a predictor of health behaviours. Delineating the psychological mechanisms linking SSES with health behaviours would be a valuable contribution toward improved understanding of socioeconomic disparities in health behaviours.

Prenatal Exposure to Nonpersistent Chemical Mixtures and Offspring IQ and Emotional and Behavioral Problems

Prenatal exposure to nonpersistent chemicals such as phthalates, bisphenols, and organophosphate (OP) pesticides is ubiquitous and occurs in mixtures. So far, epidemiological studies investigating neurodevelopmental consequences of these exposures have mainly been restricted to single-pollutant models. Thus, we studied the association between prenatal exposure to nonpersistent chemical mixtures and child IQ and emotional and behavioral problems. Data came from 782 mother-child pairs. Eleven phthalate, one bisphenol, and five OP pesticide urinary exposure biomarkers were measured three times during pregnancy and averaged. Nonverbal IQ, internalizing and attention problems, aggressive behavior, and autistic traits were assessed at child age 6 years. We used quantile g-computation to estimate the change in each outcome per quartile increase in all chemicals within the mixture. Higher exposure to the mixture was associated with lower nonverbal IQ (-4.0 points (95%CI = -7.0, -1.0), -5.5 points (95%CI = -10.2, -0.9), and -4.6 points (95%CI = -10.8, 1.5) for the second, third, and fourth quartile, respectively, compared to the first quartile). These results were mainly driven by the phthalate mixture. No association was observed with emotional and behavioral problems. Prenatal exposure to nonpersistent chemical mixtures was associated with lower nonverbal IQ in children. Exposure to chemical mixtures during gestation is universal and may impact neurodevelopment.

An epigenetic predictor of death captures multi-modal measures of brain health

Individuals of the same chronological age exhibit disparate rates of biological ageing. Consequently, a number of methodologies have been proposed to determine biological age and primarily exploit variation at the level of DNA methylation (DNAm). A novel epigenetic clock, termed 'DNAm GrimAge' has outperformed its predecessors in predicting the risk of mortality as well as many age-related morbidities. However, the association between DNAm GrimAge and cognitive or neuroimaging phenotypes remains unknown. We explore these associations in the Lothian Birth Cohort 1936 (n = 709, mean age 73 years). Higher DNAm GrimAge was strongly associated with all-cause mortality over the eighth decade (Hazard Ratio per standard deviation increase in GrimAge: 1.81, P < 2.0 × 10-16). Higher DNAm GrimAge was associated with lower age 11 IQ (β = -0.11), lower age 73 general cognitive ability (β = -0.18), decreased brain volume (β = -0.25) and increased brain white matter hyperintensities (β = 0.17). There was tentative evidence for a longitudinal association between DNAm GrimAge and cognitive decline from age 70 to 79. Sixty-nine of 137 health- and brain-related phenotypes tested were significantly associated with GrimAge. Adjusting all models for childhood intelligence attenuated to non-significance a small number of associations (12/69 associations; 6 of which were cognitive traits), but not the association with general cognitive ability (33.9% attenuation). Higher DNAm GrimAge associates with lower cognitive ability and brain vascular lesions in older age, independently of early-life cognitive ability. This epigenetic predictor of mortality associates with different measures of brain health and may aid in the prediction of age-related cognitive decline.

Intelligence, health and death

The field of cognitive epidemiology studies the prospective associations between cognitive abilities and health outcomes. We review research in this field over the past decade and describe how our understanding of the association between intelligence and all-cause mortality has consolidated with the appearance of new, population-scale data. To try to understand the association better, we discuss how intelligence relates to specific causes of death, diseases/diagnoses and biomarkers of health through the adult life course. We examine the extent to which mortality and health associations with intelligence might be attributable to people's differences in education, other indicators of socioeconomic status, health literacy and adult environments and behaviours. Finally, we discuss whether genetic data provide new tools to understand parts of the intelligence-health associations. Social epidemiologists, differential psychologists and behavioural and statistical geneticists, among others, contribute to cognitive epidemiology; advances will occur by building on a common cross-disciplinary knowledge base.

Cognitive Performance and Its Associations with Dental Caries: Results from the Dental, Oral, Medical Epidemiological (DOME) Records-Based Nationwide Study

Relatively few studies have analyzed the association between cognitive performance and dental status. This study aimed to analyze the association between cognitive performance and dental caries. Included were data from the dental, oral, medical epidemiological (DOME) study; cross-sectional records-based research, which integrated large socio-demographic, medical, and dental databases of a nationally representative sample of young to middle-aged military personnel (N = 131,927, mean age: 21.8 ± 5.9 years, age range: 18-50). The cognitive function of draftees is routinely measured at age 17 years using a battery of psychometric tests termed general intelligence score (GIS). The mean number of decayed teeth exhibited a gradient trend from the lowest (3.14 ± 3.58) to the highest GIS category (1.45 ± 2.19) (odds ratio (OR) lowest versus highest = 5.36 (5.06-5.68), p < 0.001). A similar trend was noted for the other dental parameters. The associations between GIS and decayed teeth persisted even after adjusting for socio-demographic parameters and health-related habits. The adjustments attenuated the OR but did not eliminate it (OR lowest versus highest = 3.75 (3.38-4.16)). The study demonstrates an association between cognitive performance and caries, independent of the socio-demographic and health-related habits that were analyzed. Better allocation of resources is recommended, focusing on populations with impaired cognitive performance in need of dental care.

Associations Between Hearing and Cognitive Abilities From Childhood to Middle Age: The National Child Development Study 1958

Previous cross-sectional findings indicate that hearing and cognitive abilities are positively correlated in childhood, adulthood, and older age. We used an unusually valuable longitudinal dataset from a single-year birth cohort study, the National Child Development Study 1958, to test how hearing and cognitive abilities relate to one another across the life course from childhood to middle age. Cognitive ability was assessed with a single test of general cognitive ability at age 11 years and again with multiple tests at age 50. Hearing ability was assessed, using a pure tone audiogram, in childhood at ages 11 and 16 and again at age 44. Associations between childhood and middle-age hearing and cognitive abilities were investigated using structural equation modelling. We found that higher cognitive ability was associated with better hearing (indicated by a lower score on the hearing ability variables); this association was apparent in childhood (r  =  -0.120, p <0.001) and middle age (r  =  -0.208, p <0.001). There was a reciprocal relationship between hearing and cognitive abilities over time: better hearing in childhood was weakly associated with a higher cognitive ability in middle age (β  =  -0.076, p  =  0.001), and a higher cognitive ability in childhood was associated with better hearing in middle age (β  =  -0.163, p <0.001). This latter, stronger effect was mediated by occupational and health variables in adulthood. Our results point to the discovery of a potentially life-long relationship between hearing and cognitive abilities and demonstrate how these variables may influence one another over time.

Tooth Loss and Dementia: A Critical Examination

Dementia is a major contributor to dependence and disability in older people, with aging societies characterized by growing numbers of people living with the condition. Dementia rates are highest in those with low education early in life, midlife hypertension, midlife hearing loss, depression, obesity, loneliness, a sedentary lifestyle, or sustained exposure to smoking or diabetes. Tooth loss is a putative risk factor for dementia which has received increasing research attention, but systematic review findings are mixed. Three main mechanisms have been proposed, involving 1) tooth loss leading to compromised nutrition and then leading to poorer central nervous system (CNS) function; 2) tooth loss resulting in fewer interocclusal contacts and so less somatosensory feedback to the CNS, leading to impaired cognition; and (3) chronic periodontitis resulting in tooth loss, but not before the inflammation has affected the CNS, impairing cognition. None of these is supported by compelling empirical evidence. Here, we use the life course approach to propose a plausible, empirically supported explanation for the associations between missing teeth and poorer cognitive function in older people. Evidence from longstanding cohort studies demonstrates that the putative association arises from cognitive function much earlier in life, in childhood. People with better childhood cognitive function have better oral health and access to routine dental care as they go through life, losing fewer teeth along the life course. They are also much more likely to have better cognitive function in old age. Their less cognitively able childhood counterparts will experience higher disease rates and poorer access to care, resulting in greater incremental tooth loss. Comparison of the 2 groups at any age from the mid-20s on will show greater numbers of missing teeth in the group who were less cognitively able in childhood. Those differences will be most pronounced in old age.

Adherence to the MIND diet is associated with 12-year all-cause mortality in older adults

Objective:

To prospectively evaluate the association of three dietary patterns: the MIND (Mediterranean-DASH diet intervention for Neurodegenerative Delay) diet; a Mediterranean-type diet and a traditional diet, with all-cause mortality over a 12-year period in an older sample.

Design:

A longitudinal birth cohort study. We ascertained dietary patterns using FFQ data at baseline (2004–2007) and mortality using linkage data. Cox regression was used to estimate mortality hazard ratios (HR) with adjustment for confounders.

Setting:

The Lothian Birth Cohort 1936 (LBC1936) study in Edinburgh, Scotland.

Participants:

Dietary patterns were ascertained in 882 participants, mean age 69·5 (±0·8) years, at baseline. During the 12-year follow-up (to October 2019), 206 deaths occurred.

Results:

In the basic-adjusted model, all three dietary patterns were significantly associated with mortality, the MIND diet and Mediterranean-type diet with a lower risk and the traditional diet with a higher risk. In fully adjusted models, MIND diet score was inversely related to all-cause mortality (HR 0·88; 95 % CI 0·79, 0·97) such that the risk of death was reduced by 12 % per unit increase in MIND diet score. Participants in the top compared with the bottom third of MIND diet score had a 37 % lower risk of death (HR 0·63; 95 % CI 0·41, 0·96). No significant associations with the Mediterranean-type or traditional dietary patterns were observed in the final multivariate model.

Conclusions:

Our findings suggest that closer adherence to the MIND diet is associated with a significantly lower risk of all-cause mortality, over 12 years of follow-up, and may constitute a valid public health recommendation for prolonged survival.

Adolescent Substance Use and the Brain: Behavioral, Cognitive and Neuroimaging Correlates

Adolescence is an important ontogenetic period that is characterized by behaviors such as enhanced novelty-seeking, impulsivity, and reward preference, which can give rise to an increased risk for substance use. While substance use rates in adolescence are generally on a decline, the current rates combined with emerging trends, such as increases in e-cigarette use, remain a significant public health concern. In this review, we focus on the neurobiological divergences associated with adolescent substance use, derived from a cross-sectional, retrospective, and longitudinal studies, and highlight how the use of these substances during adolescence may relate to behavioral and neuroimaging-based outcomes. Identifying and understanding the associations between adolescent substance use and changes in cognition, mental health, and future substance use risk may assist our understanding of the consequences of drug exposure during this critical window.

Phthalate and Bisphenol Exposure during Pregnancy and Offspring Nonverbal IQ

BACKGROUND

Prenatal exposures to phthalates and bisphenols are associated with impaired brain development in animals. However, epidemiological studies investigating the association between prenatal phthalate or bisphenol exposure and cognition have produced mixed findings and mostly had modest sample sizes and measured the exposure during the third trimester.

OBJECTIVE

We examined the association between pregnancy maternal urinary biomarkers of phthalate or bisphenol exposure and nonverbal intelligence quotient (IQ) in children 6 years of age.

METHOD

The study sample consisted of 1,282 mother-child pairs participating in the Generation R Study, a population-based birth cohort in Rotterdam, Netherlands (enrollment 2002-2006). We measured maternal urinary concentrations of 18 phthalate metabolites and 8 bisphenols at < 18 , 18-25, and > 25  wks of gestation. Child nonverbal IQ was measured at 6 years of age using the Snijders-Oomen Nonverbal Intelligence Test-Revised. Linear regression models were fit for each of the three collection phases separately, the three collection phases jointly, and for the averaged prenatal exposure across pregnancy.

RESULTS

Higher urinary concentrations of phthalate metabolites during early pregnancy were associated with lower child nonverbal IQ score [e.g., B per 10-fold increase in summed low-molecular weight phthalates = - 1.7 (95% CI: - 3.1 , - 0.3 )]. This association remained unchanged when adjusted for mid and late pregnancy exposures. We also observed an inverse association between late pregnancy di-n-octyl phthalate (DNOP) exposure and nonverbal IQ. Maternal urinary concentrations of bisphenols were not associated with child nonverbal IQ. There was no effect estimate modification by sex.

CONCLUSIONS

We did not observe that maternal biomarkers of bisphenol exposure are associated with nonverbal IQ. We found that phthalate exposure in early pregnancy and DNOP exposure in late pregnancy are associated with lower nonverbal IQ scores in children. Our results might suggest that particularly early pregnancy is a sensitive window of phthalate exposure, but future studies are needed to replicate our findings. https://doi.org/10.1289/EHP6047.

Body mass index and height in relation to type 2 diabetes by levels of intelligence and education in a large cohort of Danish men

Socioeconomic status (SES) is inversely associated with risks of type 2 diabetes (T2D). We investigated if young men's cognitive function, measured by intelligence test scores and educational level, as determinants of SES modified associations between body mass index (BMI) and height with the risk of T2D. 369 989 young men from the Danish Conscription Database born between 1939 and 1959 with information on measured height, weight, intelligence test scores, and education were linked to the Danish National Patient Register. During follow-up from 1977 through 2015, T2D was recorded in 32 188 men. Hazard ratios (HR) and 95% confidence intervals (95% CI) were estimated by Cox regressions. BMIs below-average (z-scores ≤ 0) were not related to risks of T2D. For BMIs above-average (z-scores > 0), positive associations between BMI and T2D were slightly stronger among men with higher intelligence test scores or longer educations than among men with lower levels of these factors (p_interaction-values < 0.004). Irrespective of BMI, incidence rates of T2D were higher among men with low levels of intelligence test score and education. Height was inversely associated with T2D (per z-score, HR = 0.96 (95% CI 0.95-0.97) and the association did not vary by intelligence test scores or education (all p_interaction-values > 0.59). While below-average BMI was not associated with T2D risk, above-average BMIs were and these association were stronger among men with high cognitive function. Nevertheless, T2D risk was higher at lower levels of cognitive function throughout the range of BMI. Height was inversely associated with T2D and it was not modified by cognitive function.

Association between intelligence quotient and disability: The role of socioeconomic status

BACKGROUND

No study has investigated the association between intelligence quotient (IQ) and disability (i.e., difficulties in activities of daily living [ADL] or instrumental activities of daily living [IADL]) in the general population.

OBJECTIVE

The goal of this nationally representative study was to analyse the potential IQ-disability association in England and identify influential factors in this association.

METHODS

Cross-sectional data were analyzed from the 2007 Adult Psychiatric Morbidity Survey (n=6872). IQ was assessed by using the National Adult Reading Test, which consists of a list of 50 words and is scored by counting the number of errors in reading the words aloud. Disability was defined as difficulties in at least 1 of the 7 domains of ADL and IADL. Regression and mediation analyses were conducted to analyze the association between IQ and disability and identify potential factors involved in this relationship, estimating odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Among the 6872 participants, the mean (SD) age was 46.9 (18.9) years; 51.8% were women. The prevalence of disability increased from 27.7% with IQ 120-129 to 51.0% with IQ 70-79. After adjusting for sex, age and ethnicity, as compared with IQ 120-129, with IQ 110-119, 100-109, 90-99, 80-89, and 70-79, the probability of disability was increased (OR 1.22 [95% CI 1.01-1.48], 1.42 [1.16-1.72], 1.86 [1.54-2.25], 2.41 [1.92-3.03], and 4.71 [3.56-6.17], respectively). In addition, we found a positive association between a 1-SD decrease in IQ and disability (OR 1.53, 95% CI 1.43-1.63). Finally, income (mediated percentage 26.9%), social class (18.0%) and education (11.6%) strongly affected the IQ-disability association, and these socioeconomic factors collectively explained 37.1% of the association.

CONCLUSIONS

Low IQ was positively associated with disability in England, and socioeconomic status explained more than one-third of this relationship.

Intelligence in young adulthood and alcohol use disorders in a prospective cohort study of Danish men: the role of psychiatric disorders and parental psychiatric history

OBJECTIVES

The aims were to estimate the association between intelligence measured in young adulthood and risk of alcohol use disorders (AUD) in men and to investigate the potential modification of this association by psychiatric disorders, parental AUD and parental psychiatric disorders.

DESIGN

Prospective cohort study based on a linkage of intelligence test scores from draft board examinations and register data on AUD diagnoses during 36 years of follow-up.

SETTING

Denmark.

PARTICIPANTS

3287 Danish men from the Copenhagen Perinatal Cohort (born 1959-1961) who appeared before the draft board at a mean age of 18.7 years.

PRIMARY OUTCOME MEASURE

First registration with AUD during follow-up was the primary outcome. Information on AUD was based on diagnoses retrieved from national hospital and outpatient treatment registers, defined according to the International Classification of Diseases.

RESULTS

361 (11.0%) men were registered with AUD during follow-up. Low intelligence scores were associated with increased odds of AUD adjusting for parental AUD, parental psychiatric disorders, maternal smoking during pregnancy, birth weight, maternal age at birth, parity and childhood socioeconomic position (OR per SD decrease in intelligence=1.69, 95% CI 1.49 to 1.92). Separate analyses indicated significant interaction (p<0.001) between intelligence and psychiatric disorders. The adjusted OR per SD decrease in intelligence score was 2.04 (95% CI 1.67 to 2.49) in men without other psychiatric disorders whereas the OR was 1.21 (95% CI 1.01 to 1.46) in men with other psychiatric disorders. No interaction was found between intelligence and parental AUD or between intelligence and parental psychiatric disorders.

CONCLUSIONS

The association between intelligence in young adulthood and AUD is modified by other psychiatric disorders as low intelligence is primarily a risk factor for men without other psychiatric disorders. Future studies should take other psychiatric disorders into account when investigating associations between intelligence and AUD.

Longitudinal associations between hearing loss and general cognitive ability: The Lothian Birth Cohort 1936

Hearing impairment is associated with poorer cognitive function in later life. We tested for the potential contribution of childhood cognitive ability to this relationship. Childhood cognitive ability is strongly related to cognitive function in older age, and may be related to auditory function through its association with hearing impairment risk factors. Using data from the Lothian Birth Cohort, 1936, we tested whether childhood cognitive ability predicted later-life hearing ability then whether this association was mediated by demographic or health differences. We found that childhood cognitive ability was negatively associated with hearing impairment risk at age 76 (odds ratio = .834, p = .042). However, this association was nonsignificant after subsequent adjustment for potentially mediating demographic and health factors. Next, we tested whether associations observed in older age between hearing impairment and general cognitive ability level or change were accounted for by childhood cognitive ability. At age 76, in the minimally adjusted model, hearing impairment was associated with poorer general cognitive ability level (β = -.119, p = .030) but was not related to decline in general cognitive ability. The former association became nonsignificant after additional adjustment for childhood cognitive ability (β = -.068, p = .426) suggesting that childhood cognitive ability contributes (potentially via demographic and health differences) to the association between levels of hearing and cognitive function in older age. Further work is needed to test whether early life cognitive ability also contributes to the association (documented in previous studies) between older-age hearing impairment and cognitive decline. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Genetic Contributions to Health Literacy

Higher health literacy is associated with higher cognitive function and better health. Despite its wide use in medical research, no study has investigated the genetic contributions to health literacy. Using 5783 English Longitudinal Study of Ageing (ELSA) participants (mean age = 65.49, SD = 9.55) who had genotyping data and had completed a health literacy test at wave 2 (2004-2005), we carried out a genome-wide association study (GWAS) of health literacy. We estimated the proportion of variance in health literacy explained by all common single nucleotide polymorphisms (SNPs). Polygenic profile scores were calculated using summary statistics from GWAS of 21 cognitive and health measures. Logistic regression was used to test whether polygenic scores for cognitive and health-related traits were associated with having adequate, compared to limited, health literacy. No SNPs achieved genome-wide significance for association with health literacy. The proportion of variance in health literacy accounted for by common SNPs was 8.5% (SE = 7.2%). Greater odds of having adequate health literacy were associated with a 1 standard deviation higher polygenic score for general cognitive ability [OR = 1.34, 95% CI (1.26, 1.42)], verbal-numerical reasoning [OR = 1.30, 95% CI (1.23, 1.39)], and years of schooling [OR = 1.29, 95% CI (1.21, 1.36)]. Reduced odds of having adequate health literacy were associated with higher polygenic profiles for poorer self-rated health [OR = 0.92, 95% CI (0.87, 0.98)] and schizophrenia [OR = 0.91, 95% CI (0.85, 0.96)). The well-documented associations between health literacy, cognitive function and health may partly be due to shared genetic etiology. Larger studies are required to obtain accurate estimates of SNP-based heritability and to discover specific health literacy-associated genetic variants.

Childhood IQ predicts age-38 oral disease experience and service-use

OBJECTIVES

Given that people with higher intelligence have been shown to live longer, enjoy better health and have more favourable health behaviours, we investigated the association between childhood IQ and a range of important dental health and service-use indicators at age 38.

METHODS

Long-standing prospective study of a complete birth cohort, with childhood IQ (assessed at ages 7, 9, 11 and 13 years) used to allocate participants (N = 818) to one of four ordinal categories of childhood IQ.

RESULTS

There were distinct and consistent gradients by childhood IQ in almost all of the dental caries experience measures (with the exception of filled teeth) whereby each was most severe in the lowest child IQ category and least severe in the highest; the exception was the mean FT score, for which there was no discernible gradient. Indicators of self-care and periodontal disease experience showed similar gradients, and multivariate modelling using the continuous IQ score confirmed the observed patterns.

CONCLUSIONS

Childhood cognitive function is a key determinant of oral health and dental service-use by midlife, with those of lower cognitive capacity as children likely to have poorer oral health, less favourable oral health-related beliefs, and more detrimental self-care and dental visiting practices by age 38. There is a need to shape dental clinical services and public health interventions so that people with the poorest cognitive function do not continue to be disadvantaged.

What genome-wide association studies reveal about the association between intelligence and physical health, illness, and mortality

The associations between higher intelligence test scores from early life and later good health, fewer illnesses, and longer life are recent discoveries. Researchers are mapping the extent of these associations and trying to understanding them. Part of the intelligence-health association has genetic origins. Recent advances in molecular genetic technology and statistical analyses have revealed that: intelligence and many health outcomes are highly polygenic; and that modest but widespread genetic correlations exist between intelligence and health, illness and mortality. Causal accounts of intelligence-health associations are still poorly understood. The contribution of education and socio-economic status - both of which are partly genetic in origin - to the intelligence-health associations are being explored.

Cognitive ability and risk of death from lower respiratory tract infection: findings from UK Biobank

Dementia increases the risk of lower respiratory tract infection, but it is unclear whether risk varies across the normal range of cognitive ability. People with higher cognitive ability tend to behave in a healthier fashion as regards risk factors for lower respiratory tract infection and there is evidence that they have a lower risk of dying from respiratory disease as a whole. We therefore investigated the relationship between cognitive ability and mortality from lower respiratory tract infection. Participants were 434,413 people from UK Biobank (54% female). Cognitive ability was measured using tests of reaction time and reasoning. Data on deaths from lower respiratory infection were obtained from death certificates. Over a mean follow-up period of 6.99 years, 1,282 people died of lower respiratory infection. Mortality from lower respiratory tract infection fell as cognitive ability increased. For a standard deviation faster reaction time, the age- and sex-adjusted hazard ratio (95% confidence interval) was 0.80 (0.76, 0.83) and the multivariable-adjusted hazard ratio was 0.87 (0.83, 0.91). There were similar though weaker associations when cognitive ability was assessed using a reasoning test. These findings suggest that variation across the normal range of cognitive ability increase risk of dying from lower respiratory tract infection.