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I J Deary

Publications and source records attributed to I J Deary.

At least 19 recordsLinked to original sources
PubMed2014

Genetics and intelligence differences: five special findings.

Intelligence is a core construct in differential psychology and behavioural genetics, and should be so in cognitive neuroscience. It is one of the best predictors of important life outcomes such as education, occupation, mental and physical health and illness, and mortality. Intelligence is one of the most heritable behavioural traits. Here, we highlight five genetic findings that are special to intelligence differences and that have important implications for its genetic architecture and for gene-hunting expeditions. (i) The heritability of intelligence increases from about 20% in infancy to perhaps 80% in later adulthood. (ii) Intelligence captures genetic effects on diverse cognitive and learning abilities, which correlate phenotypically about 0.30 on average but correlate genetically about 0.60 or higher. (iii) Assortative mating is greater for intelligence (spouse correlations ~0.40) than for other behavioural traits such as personality and psychopathology (~0.10) or physical traits such as height and weight (~0.20). Assortative mating pumps additive genetic variance into the population every generation, contributing to the high narrow heritability (additive genetic variance) of intelligence. (iv) Unlike psychiatric disorders, intelligence is normally distributed with a positive end of exceptional performance that is a model for 'positive genetics'. (v) Intelligence is associated with education and social class and broadens the causal perspectives on how these three inter-correlated variables contribute to social mobility, and health, illness and mortality differences. These five findings arose primarily from twin studies. They are being confirmed by the first new quantitative genetic technique in a century-Genome-wide Complex Trait Analysis (GCTA)-which estimates genetic influence using genome-wide genotypes in large samples of unrelated individuals. Comparing GCTA results to the results of twin studies reveals important insights into the genetic architecture of intelligence that are relevant to attempts to narrow the 'missing heritability' gap.

Genetic Predisposition to Disease↗
PubMed2007

IQ in early adulthood and later cancer risk: cohort study of one million Swedish men.

BACKGROUND: While several studies have reported an inverse relation between IQ and total mortality rates, little is known about the association, if any, between IQ and disease-specific outcomes, particularly cancer. METHODS: A cohort of 959,540 Swedish men who underwent IQ testing at military conscription at around 19 years of age, and who were followed for incident cancer. Hazards ratios for the relation between IQ and 20 cancer outcomes were computed using Cox regression. RESULTS: During an average of 19.5 years of follow-up, there were 10 273 new cancer cases. IQ showed few associations with the cancer end points studied. There was a suggestion that IQ was positively associated with lung cancer, and inversely related to stomach, oesophageal and liver malignancies, although effects were modest. The only robust gradient was found for IQ in relation to skin cancer (HRper one standard deviation advantage in IQ; 95% confidence interval 1.18; 1.13, 1.24; P value for trend across categories: <0.01), which was attenuated but retained statistical significance after adjustment for indices of socioeconomic position across the life course. CONCLUSIONS: In this large cohort of Swedish men followed into middle age, IQ was related to very few of the cancer outcomes under investigation. This indicates that the recent observation that low IQ is related to increased mortality rates may not be generated by an IQ-cancer gradient. Given that the present analyses are among the first to examine these associations, replication is required.

Adolescent↗
PubMed2006

The effects of acute hypoglycaemia on memory acquisition and recall and prospective memory in type 1 diabetes.

AIMS/HYPOTHESIS: Global memory performance is impaired during acute hypoglycaemia. This study assessed whether moderate hypoglycaemia disrupts learning and recall in isolation, and utilised a novel test of prospective memory which may better reflect the role of memory in daily life than conventional tests. SUBJECTS AND METHODS: Thirty-six subjects with type 1 diabetes participated, 20 with normal hypoglycaemia awareness (NHA) and 16 with impaired hypoglycaemia awareness (IHA). Each underwent a hypoglycaemic clamp with target blood glucose 2.5 mmol/l. Prior to hypoglycaemia, subjects attempted to memorise instructions for a prospective memory task, and recall was assessed during hypoglycaemia. Subjects then completed the learning and immediate recall stages of three conventional memory tasks (word recall, story recall, visual recall) during hypoglycaemia. Euglycaemia was restored and delayed memory for the conventional tasks was tested. The same procedures were completed in euglycaemic control studies (blood glucose 4.5 mmol/l). RESULTS: Hypoglycaemia impaired performance significantly on the prospective memory task (p = 0.004). Hypoglycaemia also significantly impaired both immediate and delayed recall for the word and story recall tasks (p < 0.01 in each case). There was no significant deterioration of performance on the visual memory task. The effect of hypoglycaemia did not differ significantly between subjects with NHA and IHA. CONCLUSIONS/INTERPRETATION: Impaired performance on the prospective memory task during hypoglycaemia demonstrates that recall is disrupted by hypoglycaemia. Impaired performance on the conventional memory tasks demonstrates that learning is also disrupted by hypoglycaemia. Results of the prospective memory task support the relevance of these findings to the everyday lives of people with diabetes.

Acute Disease↗
PubMed2006

Childhood IQ and deaths up to middle age: The Newcastle Thousand Families Study.

OBJECTIVES: To test the hypothesis that an association exists between childhood IQ (at age 11) and mortality up to middle age. STUDY DESIGN: The Newcastle Thousand Families study, a prospectively followed cohort, originally consisted of all 1142 births in the city of Newcastle in May and June 1947. Using data on 717 members of this cohort, we investigated the associations between the results of tests of IQ and English and arithmetic ability at age 11 years and mortality up to the end of 2003 using Cox's proportional hazards models. RESULTS: Childhood IQ was significantly related to mortality in men (hazard ratio 0.57 for a standard deviation change in IQ at age 11; 95% CI 0.37, 0.86; P=0.007), but not in women (hazard ratio 0.79; 95% CI 0.49, 1.27; P=0.33). Adjustment for social class at birth had little effect on the associations. Similar results were seen when using the English and arithmetic scores. CONCLUSIONS: These results confirm a recently reported association between individual differences in childhood cognition and mortality up to middle age, independent of childhood socio-economic circumstances. It is possible that the link between IQ and mortality is in part mediated through later life choices. Further research is required to identify the mechanisms by which such an association may occur, and to provide input to health promotion and disease management strategies that may improve health throughout life.

Adolescent↗
PubMed2006

Childhood IQ in relation to obesity and weight gain in adult life: the National Child Development (1958) Study.

OBJECTIVE: To examine the relation of childhood intelligence (IQ) test results with obesity in middle age and weight gain across the life course. METHODS: We analysed data from the National Child Development (1958) Study, a prospective cohort study of 17 414 births to parents residing in Great Britain in the late 1950s. Childhood IQ was measured at age 11 years and body mass index (BMI), an indicator of adiposity, was assessed at 16, 23, 33 and 42 years of age. Logistic regression (in which BMI was categorised into obese and non-obese) and structural equation growth curve models (in which BMI was retained as a continuous variable) were used to estimate the relation between childhood IQ and adult obesity, and childhood IQ and weight gain, respectively. RESULTS: In unadjusted analyses, lower childhood IQ scores were associated with an increased prevalence of adult obesity at age 42 years. This relation was somewhat stronger in women (OR(per SD decrease in IQ score) [95% CI]: 1.38 [1.26, 1.50]) than men (1.26 [1.15, 1.38]). This association remains statistically significant after adjusting for childhood characteristics, including socio-economic factors, but was heavily attenuated following control for adult characteristics, particularly education (women: 1.11 [0.99, 1.25]; men: 1.10 [0.98, 1.23]). When weight gain between age 16 and 42 years was the outcome of interest, structural equation modelling revealed that education and dietary characteristics in adult life mediated the association with childhood IQ. CONCLUSIONS: A lower IQ score in childhood is associated with obesity and weight gain in adulthood. In the present study, this relation appears to be largely mediated via educational attainment and the adoption of healthy diets in later life.

Adolescent↗
PubMed2006

White matter integrity and cognition in childhood and old age.

OBJECTIVE: To test the hypothesis that white matter integrity, as measured by diffusion tensor and magnetization transfer MRI is significantly associated with cognitive ability measured in youth and old age. METHODS: Forty, nondemented, surviving participants of the Scottish Mental Survey of 1932 underwent brain MRI and a battery of psychometric tests covering major cognitive domains and tests of information processing efficiency. IQ scores were available from age 11. Mean diffusivity, fractional anisotropy (FA), and magnetization transfer ratio (MTR) were measured in frontal and parieto-occipital white matter and centrum semiovale. RESULTS: Centrum semiovale FA correlated (r = 0.36 to 0.56; p < 0.02) with contemporaneous (age 83) scores on psychometric tests of nonverbal reasoning, working memory, executive function, and information processing efficiency. Centrum semiovale FA also correlated with IQ at age 11 (r = 0.37; p = 0.02). Controlling for IQ at age 11 and information processing at age 83 attenuated the association between centrum semiovale FA and general cognitive ability by approximately 85%. MTR, largely, did not show significant correlations with cognitive test scores. CONCLUSIONS: These data support the information processing efficiency hypothesis of cognitive aging and suggest one foundation for individual differences in processing efficiency. They also suggest that studies of imaging and cognition in the elderly should take into account prior mental ability rather than assuming that any associations between imaging parameters and cognitive test scores are the result of age-related changes.

Aged, 80 and over↗
PubMed2006

The brain-derived neurotrophic factor Val66Met polymorphism is associated with age-related change in reasoning skills.

A polymorphism (Val66Met) in the gene encoding brain-derived neurotrophic factor (BDNF) has previously been associated with impaired hippocampal function and scores on the Logical Memory subtest of the Wechsler Memory Scale-Revised (WMS-R). Despite its widespread expression in the brain, there have been few studies examining the role of BDNF on cognitive domains, other than memory. We examined the association between BDNF Val66Met genotype and non-verbal reasoning, as measured by Raven's standard progressive matrices (Raven), in two cohorts of relatively healthy older people, one aged 79 (LBC1921) and the other aged 64 (ABC1936) years. LBC1921 and ABC1936 subjects had reasoning measured at age 11 years, using the Moray House Test (MHT), in the Scottish Mental Surveys of 1932 and 1947, respectively. BDNF genotype was significantly associated with later life Raven scores, controlling for sex, age 11 MHT score and cohort (P = 0.001). MHT, Verbal Fluency and Logical Memory scores were available, in later life, for LBC1921 only. BDNF genotype was significantly associated with age 79 MHT score, controlling for sex and age 11 MHT score (P = 0.016). In both significant associations, Met homozygotes scored significantly higher than heterozygotes and Val homozygotes. This study indicates that BDNF genotype contributes to age-related changes in reasoning skills, which are closely related to general intelligence.

Aged↗
PubMed2006

Information processing in patients with intracranial tumours: A preliminary evaluation of the clinical utility of inspection time.

Psychomotor slowing is a common feature in many patients with intracranial tumours. We therefore performed a preliminary study to determine if inspection time, a measure of the efficiency of the brain's information processing, was impaired in patients with intracranial tumours. Inspection time, and some other neuropsychological and functional tests, were compared in 23 people with intracranial tumours and 24 spinal surgery controls prior to surgery. Groups were matched for sex, age and education. Inspection time scores were poorer in the brain tumour group (p < 0.003) and the effect size was moderate (eta2 = 0.197). The brain tumour group also had lower scores on the Boston Aphasia Severity Rating Scale, more anxiety on the Hospital Anxiety Depression Scales, but better Karnovsky Performance scores. Other cognitive and functional tests showed no significant differences between the groups, although group sizes were small. There were no significant changes in inspection time after spinal surgery; however, after intracranial tumour surgery, approximately 30% of patients showed no change, 30% deteriorated and 40% improved. This preliminary study suggests that recording inspection time, in a neuro-oncological setting, may prove informative and practically useful in assessing non-motor processing speed in people with brain tumours.

Brain Neoplasms↗
PubMed2006

Attentional functioning is impaired during acute hypoglycaemia in people with Type 1 diabetes.

AIMS: To examine the effects of acute insulin-induced hypoglycaemia on different aspects of attention and on general non-verbal reasoning in people with Type 1 diabetes. METHODS: A hyperinsulinaemic glucose clamp was used to maintain euglycaemia (4.5 mmol/l) or induce hypoglycaemia (2.6 mmol/l) on separate occasions in 16 adults with Type 1 diabetes each of whom were studied on two occasions in a counterbalanced order. During each study condition, the subjects completed parallel tests of cognitive function assessed by the Test of Everyday Attention and the Raven's Progressive Matrices. RESULTS: Hypoglycaemia caused a significant deterioration in tests sensitive to visual and auditory selective attention. During hypoglycaemia, attentional flexibility deteriorated and speed of information processing was delayed. Sustained attention and intelligence scores were preserved during hypoglycaemia. CONCLUSIONS: In people with Type 1 diabetes, hypoglycaemia causes a significant deterioration in attentional abilities, while non-verbal reasoning is preserved. It is likely therefore that many complex cognitive tasks which involve attention will be impaired during moderate hypoglycaemia during everyday life.

Acute Disease↗
PubMed2005

Association between genotype at an exonic SNP in DISC1 and normal cognitive aging.

DISC1 is expressed in the hippocampus and has been identified as a possible genetic risk factor for both schizophrenia and bipolar disorder. These psychiatric illnesses are associated with impaired learning and memory. This study investigates the association of variation in DISC1 with cognitive function on the same general mental ability test (Moray House Test) at age 11 and age 79, and cognitive change between ages 11 and 79, in 425 people from the Lothian Birth Cohort 1921 (LBC1921). Tests of memory, non-verbal reasoning and executive function were also administered at age 79. The effect of genotype at a non-synonymous single nucleotide polymorphism in exon 11, rs821616, was studied. There was no direct effect of DISC1 genotype on any cognitive measure. However, there was a significant DISC1 genotype by sex interaction on Moray House Test scores at age 79, both before and after adjustment for cognitive ability at age 11 (p = 0.034 and 0.043, respectively). Women homozygous for the Cys allele had significantly lower cognitive ability scores than men at age 79, p = 0.003. Variation in DISC1 may therefore affect cognitive aging especially in women.

Aged↗
PubMed2005

Cognitive correlates of cerebral white matter lesions and water diffusion tensor parameters in community-dwelling older people.

BACKGROUND: The biological basis of cognitive ageing is unknown. One underlying process might be disruption of white matter tracts connecting cortical regions. White matter lesions (WML) seen on structural MRI may disrupt cortical connections, but diffusion tensor MRI (DT-MRI) parameters - mean diffusivity ( ) and fractional anisotropy (FA) - may reflect more subtle changes in white matter integrity. Here the relationships between WML load, DT-MRI parameters and cognition in a large cohort of elderly subjects with a very narrow age range were investigated. METHODS: 105 community-dwelling volunteers underwent MRI and neuropsychological assessment. Seventy-two (68.6%) were female, and their mean age was 78.4 (SD 1.5) years. Scans were rated for WML load. and FA were measured from regions of interest in normal-appearing frontal and occipital white matter, and centrum semiovale. RESULTS: and FA differed significantly among the three brain regions studied (p << 0.01). increased with age (r = 0.22 to 0.35, p < 0.03), and was negatively correlated with FA (r = -0.20 to -0.51, p < 0.05) in all three regions. There was a trend towards increased WML load correlating with poorer cognitive function, and this was statistically significant for the Mini-Mental State Examination (rho = -0.23, p = 0.02). was generally negatively correlated with cognitive test score, and FA was positively correlated. This pattern was more consistent for than for FA, and particularly for verbal fluency ( : r = -0.22 to -0.27, p < 0.03), which measures executive function. CONCLUSIONS: DT-MRI parameters, in particular , are sensitive to early ultrastructural changes underlying cognitive ageing. Executive function may be the cognitive domain most sensitive to age-related decline in white matter tract integrity.

Aged↗
PubMed2005

Childhood IQ of parents related to characteristics of their offspring: linking the Scottish Mental Survey 1932 to the Midspan Family Study.

The objective of the study was to investigate the relationship between childhood IQ of parents and characteristics of their adult offspring. It was a prospective family cohort study linked to a mental ability survey of the parents and set in Renfrew and Paisley in Scotland. Participants were 1921-born men and women who took part in the Scottish Mental Survey in 1932 and the Renfrew/Paisley study in the 1970s, and whose offspring took part in the Midspan Family study in 1996. There were 286 offspring from 179 families. Parental IQ was related to some, but not all characteristics of offspring. Greater parental IQ was associated with taller offspring. Parental IQ was inversely related to number of cigarettes smoked by offspring. Higher parental IQ was associated with better education, offspring social class and offspring deprivation category. There were no significant relationships between parental IQ and offspring systolic blood pressure, diastolic blood pressure, cholesterol, glucose, lung function, weight, body mass index, waist hip ratio, housing, alcohol consumption, marital status, car use and exercise. Structural equation modelling showed parental IQ associated with offspring education directly and mediated via parental social class. Offspring education was associated with offspring smoking and social class. The smoking finding may have implications for targeting of health education.

Adult↗
PubMed2005

Childhood IQ and all-cause mortality before and after age 65: prospective observational study linking the Scottish Mental Survey 1932 and the Midspan studies.

OBJECTIVES: The objective was to investigate how childhood IQ related to all-cause mortality before and after age 65. DESIGN: The Midspan prospective cohort studies, followed-up for mortality for 25 years, were linked to individuals' childhood IQ from the Scottish Mental Survey 1932. METHODS: The Midspan studies collected data on risk factors for cardiorespiratory disease from a questionnaire and at a screening examination, and were conducted on adults in Scotland in the 1970s. An age 11 IQ from the Scottish Mental Survey 1932, a cognitive ability test conducted on 1921-born children attending schools in Scotland, was found for 938 Midspan participants. The relationship between childhood IQ and mortality risk, adjusting for adulthood socio-economic confounders, was analysed. The effect of adjustment for childhood IQ on the relationship between established risk factors (blood pressure, smoking, height and respiratory function) and mortality was also investigated. RESULTS: For deaths occurring up to age 65, there was a 36% increased risk per standard deviation decrease (15 points) in childhood IQ which was reduced to 29% after adjusting for social class and deprivation category. There was no statistically significant relationship between childhood IQ and deaths occurring after the age of 65. Adjustment for childhood IQ attenuated the risk factor-mortality relationship in deaths occurring up to age 65, but had no effect in deaths occurring after age 65. CONCLUSIONS: Childhood IQ was significantly related to deaths occurring up to age 65, but not to deaths occurring after age 65.

Adolescent↗
PubMed2004

Pronunciation of irregular words is preserved in dementia, validating premorbid IQ estimation.

The National Adult Reading Test (NART), used to estimate premorbid mental ability, involves pronunciation of irregular words. The authors demonstrate that, after controlling for age 11 IQ test scores, mean NART scores do not differ in people with and without dementia. The correlation between age 11 IQ and NART scores at about age 80 was similar in the groups with (r = 0.63, p < 0.001) and without (r = 0.60, p < 0.001) dementia. These findings validate the NART as an estimator of premorbid ability in mild to moderate dementia.

Aged↗
PubMed2004

Childhood IQ and cardiovascular disease in adulthood: prospective observational study linking the Scottish Mental Survey 1932 and the Midspan studies.

This study investigated the influence of childhood IQ on the relationships between risk factors and cardiovascular disease (CVD), coronary heart disease (CHD) and stroke in adulthood. Participants were from the Midspan prospective cohort studies which were conducted on adults in Scotland in the 1970s. Data on risk factors were collected from a questionnaire and at a screening examination, and participants were followed up for 25 years for hospital admissions and mortality. 938 Midspan participants were successfully matched with their age 11 IQ from the Scottish Mental Survey 1932, in which 1921-born children attending schools in Scotland took a cognitive ability test. Childhood IQ was negatively correlated with diastolic and systolic blood pressure, and positively correlated with height and respiratory function in adulthood. For each of CVD, CHD and stroke, defined as either a hospital admission or death, there was an increased relative rate per standard deviation decrease (15 points) in childhood IQ of 1.11 (95% confidence interval 1.01-1.23), 1.16 (1.03-1.32) and 1.10 (0.88-1.36), respectively. With events divided into those first occurring before and those first occurring after the age of 65, the relationships between childhood IQ and CVD, CHD and stroke were only seen before age 65 and not after age 65. Blood pressure, height, respiratory function and smoking were associated with CVD events. Relationships were stronger in the early compared to the later period for smoking and FEV1, and stronger in the later compared to the earlier period for blood pressure. Adjustment for childhood IQ had small attenuating effects on the risk factor-CVD relationship before age 65 and no effects after age 65. Adjustment for risk factors attenuated the childhood IQ-CVD relationship by a small amount before age 65. Childhood IQ was associated with CVD risk factors and events and can be considered an important new risk factor.

Adolescent↗
PubMed2004

The Voice Symptom Scale (VoiSS) and the Vocal Handicap Index (VHI): a comparison of structure and content.

Self report measures of voice function are in frequent use, but have had inadequate psychometric evaluation. We aimed to perform a substantial factor analysis of two measures of voice impairment, the Voice Symptom Scale (VoiSS) and the Voice Handicap Index (VHI). Both the 30-item questionnaires were completed by 319 dysphonic voice clinic attenders (99M, 220F). Principal components analysis confirmed that both instruments reflected general voice abnormality. The VoiSS comprised three factors - impairment (15 items), emotional (8 items) and related physical symptoms (7 items) - each with a good internal consistency. Analysis of the VHI suggested that it contains only two subscales. When a three-factor solution was imposed on the data, analysis failed to support the currently advised three 10-item subscale interpretations. Instead, we found a physical (voice impairment) domain (8 items), a psychosocial domain (14 items) and a factor with 8 items related to difficulty in being heard. The VHI requires further statistical refinement to identify its subscale structure. The VoiSS was developed from 800 subjects and is psychometrically the most robust and extensively validated self report voice measure available.

Adult↗