Fall in association of height with intelligence and educational level

Weakening of the cognition and height association from 1957 to 2018: Findings from four British birth cohort studies

Background

Taller individuals have been repeatedly found to have higher scores on cognitive assessments. Recent studies have suggested that this association can be explained by genetic factors, yet this does not preclude the influence of environmental or social factors that may change over time. We thus tested whether the association changed across time using data from four British birth cohorts (born in 1946, 1958, 1970, and 2001).

Methods

In each cohort height was measured and cognition via verbal reasoning, vocabulary/comprehension, and mathematical tests; at ages 10/11 and 14/17 years (N=41,418). We examined associations between height and cognition at each age, separately in each cohort, and for each cognitive test administered. Linear and quantile regression models were used.

Results

Taller participants had higher mean cognitive assessment scores in childhood and adolescence, yet the associations were weaker in later (1970 and 2001) cohorts. For example, the mean difference in height comparing the highest with lowest verbal cognition scores at 10/11 years was 0.57 SD (95% CI = 0.44-0.70) in the 1946 cohort, yet 0.30 SD (0.23-0.37) in the 2001 cohort. Expressed alternatively, there was a reduction in correlation from 0.17 (0.15-0.20) to 0.08 (0.06-0.10). This pattern of change in the association was observed across all ages and cognition measures used, was robust to adjustment for social class and parental height, and modeling of plausible missing-not-at-random scenarios. Quantile regression analyses suggested that these differences were driven by differences in the lower centiles of height, where environmental influence may be greatest.

Conclusions

Associations between height and cognitive assessment scores in childhood-adolescence substantially weakened from 1957-2018. These results support the notion that environmental and social change can markedly weaken associations between cognition and other traits.

Funding

DB is supported by the Economic and Social Research Council (grant number ES/M001660/1); DB and LW by the Medical Research Council (MR/V002147/1). The Medical Research Council (MRC) and the University of Bristol support the MRC Integrative Epidemiology Unit [MC_UU_00011/1]. NMD is supported by an Norwegian Research Council Grant number 295989. VM is supported by the CLOSER Innovation Fund WP19 which is funded by the Economic and Social Research Council (award reference: ES/K000357/1) and Economic and Social Research Council (ES/M001660/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Association of motor index scores with fall incidence among community-dwelling older people

BACKGROUND

Several kinds of motor dysfunction have been studied for predicting future fall risk in community-dwelling older individuals. However, no study has tested the ability of the fine motor index (FINEA) and gross motor index (GROSSA) to predict the risk of falling, as well as the specific fall type.

OBJECTIVE

We investigated the associations of FINEA/GROSSA scores with fall risk, explained falls, and unexplained falls.

METHODS

A total of 6267 community-dwelling adults aged ≥ 50 years from the Irish Longitudinal Study on Aging (TILDA) cohort were included. First, the associations of FINEA and GROSSA scores with the history of total falls, explained falls and unexplained falls were assessed in a cross-sectional study and further verified in a prospective cohort after 2 years of follow-up by Poisson regression analysis.

RESULTS

We found that high FINEA and GROSSA scores were positively associated with almost all fall histories (FINEA scores: total falls: adjusted prevalence ratio [aPR] = 1.28, P = 0.009; explained falls: aPR = 1.15, P = 0.231; unexplained falls: aPR = 1.88, P < 0.001; GROSSA scores: total falls: aPR = 1.39, P < 0.001; explained falls: aPR = 1.28, P = 0.012; unexplained falls: aPR = 2.18, P < 0.001) in a cross-sectional study. After 2 years of follow-up, high FINEA scores were associated with an increased incidence of total falls (adjusted rate ratio [aRR] = 1.42, P = 0.016) and explained falls (aRR = 1.51, P = 0.020) but not with unexplained falls (aRR = 1.41, P = 0.209). High GROSSA scores were associated with an increased incidence of unexplained falls (aRR = 1.57, P = 0.041) and were not associated with either total falls (aRR = 1.21, P = 0.129) or explained falls (aRR = 1.07, P = 0.656). Compared with individuals without limitations in either the FINEA or GROSSA, individuals with limitations in both indices had a higher risk of falls, including total falls (aRR = 1.35, P = 0.002), explained falls (aRR = 1.31, P = 0.033) and unexplained falls (aRR = 1.62, P = 0.004).

CONCLUSION

FINEA scores were positively associated with accidental falls, while GROSSA scores were positively associated with unexplained falls. The group for whom both measures were impaired showed a significantly higher risk of both explained and unexplained falls. FINEA or GROSSA scores should be investigated further as possible tools to screen for and identify community-dwelling adults at high risk of falling.

The secular trend of intelligence test scores: The Danish experience for young men born between 1940 and 2000

The present study investigated the Danish secular trend of intelligence test scores among young men born between 1940 and 2000, as well as the possible associations of birth cohort changes in family size, nutrition, education, and intelligence test score variability with the increasing secular trend. The study population included all men born from 1940 to 2000 who appeared before a draft board before 2020 (N = 1,556,770). At the mandatory draft board examination, the approximately 19-year-old men underwent a medical examination and an intelligence test. In the statistical analyses, the IQ mean and standard deviation (SD) were estimated separately for each of the included annual birth cohorts based on information from birth cohorts with available total intelligence test scores for all tested individuals (i.e. 1940-1958 and 1987-2000; the mean and SD were interpolated for the intermediate birth cohorts). Moreover, the possible associations with birth cohort changes in family size, height as a proxy for nutritional status, education, and IQ variability were investigated among those birth cohorts for whom a secular increase in intelligence test scores was found. The results showed that the estimated mean IQ score increased from a baseline set to 100 (SD: 15) among individuals born in 1940 to 108.9 (SD: 12.2) among individuals born in 1980, since when it has decreased. Focusing on the birth cohorts of 1940-1980, for whom a secular increase in intelligence test scores was found, birth cohort changes in family size, height, and education explained large proportions of the birth cohort variance in mean intelligence test scores, suggesting that these factors may be important contributors to the observed Flynn effect in Denmark.

Association of height and violent criminality: results from a Swedish total population study

BACKGROUND

Violent criminality is at least moderately heritable, but the mechanisms behind this remain largely unexplained. Height, a highly heritable trait, may be involved but no study has estimated the effect of height on crime while simultaneously accounting for important demographic, biological and other heritable confounders.

METHODS

We linked nationwide, longitudinal registers for 760 000 men who underwent mandatory military conscription from 1980 through 1992 in Sweden, to assess the association between height and being convicted of a violent crime. We used Cox proportional hazard modelling and controlled for three types of potential confounders: physical characteristics, childhood demographics and general cognitive ability (intelligence).

RESULTS

In unadjusted analyses, height had a moderate negative relationship to violent crime; the shortest of men were twice as likely to be convicted of a violent crime as the tallest. However, when simultaneously controlling for all measured confounders, height was weakly and positively related to violent crime. Intelligence had the individually strongest mitigating effect on the height-crime relationship.

CONCLUSIONS

Although shorter stature was associated with increased risk of violent offending, our analyses strongly suggested that this relationship was explained by intelligence and other confounding factors. Hence, it is unlikely that height, a highly heritable physical characteristic, accounts for much of the unexplained heritability of violent criminality.

Effects of topical administration of nimodipine on cerebral blood flow following subarachnoid hemorrhage in pigs

We sought to explore whether topical administration of nimodipine improves the abnormal cerebral perfusion following subarachnoid hemorrhage (SAH) in pigs. Fourteen pigs were randomly divided into three groups: sham (n=4), SAH (n=5), or SAH + nimodipine (n=5). The SAH model was established by injecting fresh autologous nonheparinized arterial blood into the suprasellae cistern. Nimodipine or saline placebo (0.04 g/mL) were administered to the operative area on the fourth day after the SAH model was established. The cerebral blood flow (CBF) was measured 60 min after topical administration of nimodipine by cranial SPECT/CT scans with 5 mCi 99mTc-ECD injected intravenously. The CCR (corticocebellar ratio) was calculated by dividing the counts/voxel of the whole cerebral hemisphere by the average count/voxel in the cerebellar region of reference and RD (relative dispersion). A predictor for impaired autoregulation of CBF was calculated by dividing standard deviation (SD) of regional perfusion by mean perfusion (RD=SD/Mean). CCR and RD were applied to describe hemisphere CBF and perfusion heterogeneity. Cerebral perfusion significantly decreased in the SAH group (CCR: 1.382±0.192, RD: 0.417±0.015) compared to sham (CCR: 1.988±0.346, RD 0.389±0.015) (p<0.05). Abnormal cerebral perfusion status, however, was not significantly improved in the nimodipine + SAH group (CCR: 1.503±0.107, RD: 0.425±0.018) compared to the SAH group (p>0.05). Topical administration of nimodipine did not significantly improve CBF following SAH. These findings were not consistent with our previous data demonstrating that the topical administration of nimodipine significantly alleviates cerebral vasospasm following SAH detected by TCD. Potential mechanisms governing these disparate outcomes require further investigation.

The Relationship between Height and Cognitive Function among Community-dwelling Elderly: Hallym Aging Study

OBJECTIVES

Height is known as an index that reflects the environment of the fetal, childhood, and adolescent periods, which affect adult health. This study was conducted to elucidate whether height is associated with cognitive impairment in community-dwelling elders in Korea.

METHODS

The study subjects were recruited among community dwelling elderly individuals aged 65 or over who participated in the 2004 Hallym Aging Study. They were invited to a general hospital and were evaluated for socioeconomic status, smoking history, and various clinical measures. Cognitive function measurement was performed using the Korean-Mini Mental State Examination. Logistic regression was used to evaluate the association between height and cognitive function.

RESULTS

After adjusting for potential covariates such as age and education, the smallest group was associated with higher risk of cognitive impairment compared with the tallest group among elderly men (odds ratio [OR], 4.20; 95% confidence interval [CI], 1.02-17.36), but not among elderly women (OR,1.65; 95% CI, 0.62-4.40).

CONCLUSIONS

The reason for this difference according to sex may be explained by the differential effects of education on cognitive function by sex. A larger population-based prospective cohort study is needed to examine the association between height and cognitive function according to sex.

Resolving the Genetic and Environmental Sources of the Correlation Between Height and Intelligence: A Study of Nearly 2600 Norwegian Male Twin Pairs

The main aim of this paper was to resolve the correlation between intelligence test scores and standing height into genetic and environmental components. Data on 1181 identical and 1412 fraternal twin pairs (all males) were retrieved by matching files from the Norwegian Army with twin registries. The data were analyzed by means of a structural equation model comprising latent genetic, shared environmental and nonshared environmental factors and correlations between them. A major part of the height–intelligence correlation was due to correlated shared environments (59% of the phenotypic height–intelligence correlation), but statistically significant effects of correlated genes and nonshared environments were also found (respectively 35% and 6% of the phenotypic correlation).

Genetic and environmental contributions to the association between anthropometric measures and iq: a study of Minnesota twins at age 11 and 17

Associations of height and head circumference with IQ are well documented, but much less is known about the association of IQ with other anthropometric measures or the mechanisms behind these associations. We therefore analyzed the associations between IQ and several anthropometric measures using a twin-study design. Twins born in Minnesota were assessed at either age 11 (756 complete pairs) or 17 (626 complete pairs) and analyzed using genetic modeling. Head circumference and height showed the most consistent positive associations with IQ, whereas more detailed anthropometric measures were not significantly better predictors of IQ. These associations were mainly due to common genetic factors. Our results suggest that the same genetic factors have an effect on physical and cognitive development. Head circumference and height capture information on children's physical development, which is partly associated also with cognitive development.

On the sources of the height-intelligence correlation: new insights from a bivariate ACE model with assortative mating

A robust positive correlation between height and intelligence, as measured by IQ tests, has been established in the literature. This paper makes several contributions toward establishing the causes of this association. First, we extend the standard bivariate ACE model to account for assortative mating. The more general theoretical framework provides several key insights, including formulas to decompose a cross-trait genetic correlation into components attributable to assortative mating and pleiotropy and to decompose a cross-trait within-family correlation. Second, we use a large dataset of male twins drawn from Swedish conscription records and examine how well genetic and environmental factors explain the association between (i) height and intelligence and (ii) height and military aptitude, a professional psychologist's assessment of a conscript's ability to deal with wartime stress. For both traits, we find suggestive evidence of a shared genetic architecture with height, but we demonstrate that point estimates are very sensitive to assumed degrees of assortative mating. Third, we report a significant within-family correlation between height and intelligence (p^ = 0.10), suggesting that pleiotropy might be at play.

Relationship between childhood short stature and academic achievement in adolescents and young adults--a longitudinal study

AIM

To determine if short stature at 14 or 21 years and patterns of 'catch-up' growth from 5 to 14 or 21 years are related to academic achievement in adolescents.

METHODS

The Mater University of Queensland Study of Pregnancy is a longitudinal study of 7223 singleton infants born between 1981 and 1984. Data were available for cross-sectional analyses of 3785 adolescents of whom 2149 were seen as young adults. Longitudinal patterns of growth were examined for 2936 subjects from 5 to 14 years and 1753 subjects from 5 to 21 years.

RESULTS

Adolescents or young adults with height <10th centile had a lower mean Wide Range Achievement Test (WRAT) score in adolescence and at 21 years than those of normal height (2.7 and 3.0 points, respectively) and increased odds of a WRAT score <85 (1.57 and 1.87, respectively) and learning difficulties (1.61 and 1.78, respectively). For growth patterns from 5 to 14 years, adolescents short at 5 years, irrespective of height at 14 years, had a lower mean WRAT score and increased odds of WRAT score <85 and learning difficulties. However, for growth patterns from 5 to 21 years, only the group short at both ages had increased learning difficulties.

CONCLUSIONS

Youth short at 14 years or at 21 years and those persistently short have an increased prevalence of academic difficulties. Catch-up growth by 21, although not 14 years, was associated with improved outcomes.

The Danish draft board's intelligence test, Børge Priens Prøve: psychometric properties and research applications through 50 years

For over 50 years the Danish draft board has used the same test, Børge Priens Prøve (BPP) for cognitive abilities, involving four paper-and-pencil subtests, to assess suitability for conscription. The potential availability of test scores has been an invaluable resource for research into factors relating to intelligence. In this article the circumstances of the original development of the test are briefly presented, followed by a description of the four subtests and the conditions of testing, scoring and result registration. Over forty studies are identified, including some unpublished, which have explored the psychometric properties of the BPP and have shown the relationships between intelligence as measured by the BPP and a wide range of biological, social and health-related factors.

Height, wealth, and health: an overview with new data from three longitudinal studies

This overview, based on a literature review and new data from the three cohorts (Whitehall Studies I and II, and the Vietnam Experience Study), has four objectives: (a) to outline the major determinants of height, so providing an indication as to what exposures this characteristic may capture; (b) to summarise, by reviewing reports from large scale studies, the relation between adult height and a range of disease outcomes--both somatic and psychiatric--with particular emphasis on coronary heart disease (CHD) and stroke; (c) to discuss why these relationships may exist, in particular, the role, if any, of socioeconomic position in explaining the apparent associations; and, finally (d) to outline future research directions in this field. The large majority of evidence for predictors of height, and its health consequences, comes from observational studies. While genetic predisposition is a major determinant of height, secular rises in childhood and adult stature across successive birth cohorts suggest that early life environment also has an important impact. Plausible non-genetic determinants of height include nutrition, illness, socioeconomic status, and psychosocial stress. Evidence for an association between height and a series of health endpoints is accumulating. Thus, shorter people appear to experience increased risk of CHD, and these associations appear to be independent of socioeconomic position and other potentially confounding variables. For stroke, and its sub-types, findings are less clear. In contrast to CHD, some cancers, such as carcinoma of the colorectum, prostate, breast (in women), central nervous system, skin, endometrium, thyroid and blood (haematopoietic) are more common in taller people. While height may be negatively related to the risk of completed suicide, conclusions about the links between stature and other health endpoints is problematic given the paucity of evidence, which should be addressed. Ultimately, for want of better data, investigators in this area have used height as a proxy for a range of pre-adult exposures. In future, research should aim to explore the predictive capacity of direct measures of diet, psychosocial stress, childhood chronic illness and so on, rather than focus on height or its components. The problem is that extended follow-up of child cohorts with such data are required, and studies which hold these data are not currently available, although several are either maturing to the point where they offer sufficient clinical outcomes to facilitate analyses or are in the advanced planning stage.

Genetic contributions to the association between height and intelligence: Evidence from Dutch twin data from childhood to middle age

A positive association between intelligence (IQ) and height has been reported previously. It is generally assumed that this association reflects the effect of childhood environment on IQ, but there is still little research supporting directly this hypothesis. We studied the association between height and IQ in 209 Dutch twin pairs at the ages of 5, 7, 10 and 12 years, 208 twin pairs at 16 and 18 years of age and 567 twin pairs and their siblings in adulthood. The heritability of height was high in all cohorts and across all ages (a2 = 0.93 - 0.96). In adulthood, heritability was also high for full-scale IQ (FSIQ: a2 = 0.83-0.84) and somewhat lower for verbal IQ (VIQ: a2 = 0.66-0.84). In early childhood, the heritability was lower, and common environmental factors had a substantial effect on FSIQ and VIQ. A positive association of height and IQ was found in early childhood and adolescence. In adulthood, a correlation was found between height and FSIQ in young adulthood and between height and VIQ in middle age. All correlations could be ascribed to genetic factors influencing both height and IQ. Thus, these results show that the association between height and IQ should not be directly regarded as evidence for childhood living conditions affecting IQ, but the effect of genetic factors affecting independently or interacting with environmental factors should be considered as well.

Smart and suicidal? The social ecology of intelligence and suicide in Austria

According to de Catanzaro's (1981) evolutionary theory of human suicide, a threshold intelligence is necessary for suicidality. A corollary deducible from this assertion is that intelligence and suicide mortality should be positively related. The present study tested de Catanzaro's corollary within a country. Using district-level IQ data of the entire non-institutionalized Austrian male year-of-birth cohort of 1969 who survived up to compulsory military conscription, including IQ testing in 1987 (n = 55474), the subsequent (1987-2001) district-level cohort loss due to suicide mortality was investigated. Across 99 Austrian districts, the regional IQ was weakly but statistically significantly, positively related to the regional standardized suicide rate as well as to the regional percentage of mortality due to suicide in this very cohort, when these relations were controlled for likely confounders (male divorce and unemployment rates and male net income), but not statistically reliable without these controls. It is argued that the most parsimonious interpretation of these aggregate-level findings remains that intelligence level and suicide mortality are positively related.

Are inequalities in height narrowing? Comparing effects of social class on height in two generations

OBJECTIVE

To determine whether social inequalities in height change across generations.

METHODS

The target population was from the 1958 British birth cohort, all born 3rd-9th March 1958, followed to 1991, and the offspring of one third of this population. Main outcomes were height measured at 7, 11, 16, and 33 years (cohort members) and once at 4-18 years (offspring). Multilevel models applied to associations of social class of origin with (a) child-to-adult growth trajectory (cohort members), (b) height (offspring), and (c) generational height increment.

RESULTS

Height inequalities were observed among cohort members, with differences >2.0 cm at all ages between classes I and II, and IV and V. By adulthood, the difference in mean height had declined significantly in boys and slightly in girls. A secular trend was seen between the two generations. While male offspring had a similar mean height to their fathers in classes I and II, boys in classes IV and V gained 2.1 cm (p<0.001). Height gains of female offspring were evident in all classes, with a greater gain in classes IV and V (non-significant). The social class effect on height was weaker among offspring, with a difference between classes I and II, and IV and V of less than 1 cm.

CONCLUSIONS

Social inequalities in height observed among the cohort weakened substantially in the next generation due to a greater height gain among offspring from manual classes. Inequalities in childhood height have narrowed between the two generations in this study.

Height of conscripts in Europe: is postneonatal mortality a predictor?

The height of conscripts has increased steadily during recent decades in Europe. We have collected data on conscript height from 11 European countries to examine if this trend is continuing. In the Scandinavian countries and The Netherlands the increase in height reached a plateau during the 1980s, while the trend towards increasing adult height continued in the middle and southern European countries. There are still large differences between the countries (1990: The Netherlands 181.2 cm and Portugal 170.3 cm), with a marked trend for the tallest conscripts to be in the north and the shortest in the shortest in the south. It has been suggested that the secular increase in adult height is mainly determined by an increase in growth during the first years of life. We examined postneonatal mortality (PNM) as a proxy for adverse environmental factors, mainly poor nutrition and infections, affecting growth during infancy, and related it to conscript height in the European countries. The general pattern was a rapid decrease in PNM until a low level was reached, after which it remained low, or decreased only very slowly. In countries where the increase in conscript height has levelled off, PNM reached a low and stable level (about 3-5 per thousand) approximately two decades before this stagnation. We speculate that the increase in height will continue in the rest of the European countries until approximately two decades after PNM has reached the same low level.

Changes in body height among selected ethnic groups

STUDY OBJECTIVE

The aim was to assess the effects of genetic factors and environmental influences on adolescence body height.

DESIGN

The study was a retrospective survey of mean standing height collected from computerised medical draft records of 17-18 year old adolescents, born between 1950 and 1971.

SETTING

All the studied population is resident of the state of Israel.

PARTICIPANTS

About half a million records of recruits were examined. The sex distribution was: 61% male, 39% female. Ethnic distribution of the studied population was according to the countries of origin: Poland 7.8%, Romania 22.0%, Yemen 11.4%, Iraq 17.5%, Morocco 27.4%, and Israel 7.8%.

MEASUREMENTS AND MAIN RESULTS

Marked differences in standing height measures were found between the ethnic groups compared to the Israeli reference group. A linear increase of 1.1 mm/year for reference males and 0.8 mm/year for the female population was found over the 22 years of study period. Ethnic groups with lower mean height were found to have a significantly greater increase in height during the period studied.

CONCLUSIONS

Israel as an immigration country may serve as a model for the study of environmental and genetic factors. Under conditions found in Israel, body height continues to increase with year of birth, while significant differences in height between ethnic groups has diminished.