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.

Is There a Correlation Between the Number of Brain Cells and IQ?

Our access to a unique material of postmortem brains obtained from decades of data collection enabled a stereological analysis of the neuron numbers and correlation of results with individual premorbid intelligence quotient (IQ) data. In our sample of 50 brains from men, we find that IQ does not correlate with the number of brain cells in the human neocortex and was only weakly correlated to brain weight. Our stereological examination extended to measures of several other parameters that might be of relevance to intelligence, including numbers of cerebral glial cells (astrocytes, oligodendrocytes, and microglia) and the volume of key areas in the gray and white matter and of the cerebral ventricles, also showing near-zero nonsignificant correlations to IQ.

Assessment of cognitive ability at conscription for the Danish army: Is a single total score sufficient?

Børge Priens Prøve (BPP) was developed for the Danish Army by psychologist Børge Prien in the 1950s, as a test of general cognitive ability for use at conscription for the Danish armed forces. The final BPP (1957) had four subtests; a Raven-like matrix subtest, and three subtests measuring verbal, numerical, and visuospatial ability. The BPP is a speeded test counting the number of correct responses within 45 minutes. Thus, we consider the BPP as a measure of "cognitive efficiency" rather than a pure measure of cognitive ability. The BPP is still in use.Using techniques available in 1960, Rasch concluded that the matrices and numerical tests appeared to satisfy the requirements of the Rasch (Probabilistic models for some intelligence and attainment tests, Danish Institute for Educational Research, Copenhagen; 1960) model, while the verbal and visuospatial tests did not. Since then, there have been, to our knowledge, no published studies of the psychometric scaling properties of the BPP, partly because the practice of the Danish draft board has been to record only the total score. We examine these properties by analysis of data from two cohorts (n = 9,491), using the Leunbach (A probabilistic measurement model for assessing whether two tests measure the same personal factor. The Danish Institute of Educational, Copenhagen, Denmark; 1976) model to assess whether the sum of the four subtests provides a statistically sufficient measure of a common latent trait. Since we found only weak evidence against fit to the Leunbach model, we claim that this warrants the use of a summarized total BPP score. We examined whether BPP subscales suffered from differential test functioning (DTF) relative to samples. Weak, and for practical purposes too weak, DTF was suggested for one subscale.

Cognitive behavioural treatment for the chronic post-traumatic headache patient: a randomized controlled trial

BACKGROUND

Chronic post-traumatic headache (CPTH) after mild head injury can be difficult to manage. Research is scarce and successful interventions are lacking.To evaluate the effect of a group-based Cognitive Behavioural Therapy (CBT) intervention in relation to headache, pain perception, psychological symptoms and quality of life in patients with CPTH.

METHODS

Ninety patients with CPTH according to ICHD-2 criteria were enrolled from the Danish Headache Center into a randomized, controlled trial. Patients were randomly assigned to either a waiting list group or to a nine-week CBT group intervention. At baseline and after 26 weeks all patients completed the Rivermead Post Concussion Symptoms Questionnaire, SF-36, SCL-90-R and a headache diary.

RESULTS

The CBT had no effect on headache and pressure pain thresholds and only a minor impact on the CPTH patients' quality of life, psychological distress, and the overall experience of symptoms. The waiting-list group experienced no change in headache but, opposed to the treatment group, a significant decrease in somatic and cognitive symptoms indicating a spontaneous remission over time.

CONCLUSIONS

Our primarily negative findings confirm that management of patients with CPTH still remains a considerable challenge. Psychological group therapy with CBT might be effective in an earlier stage of CPTH and in less severely affected patients but our findings strongly underline the need for randomized controlled studies to test the efficacy of psychological therapy.

Adult cognitive ability and educational level in relation to concussions in childhood and adolescence: a population study of young men

OBJECTIVE

To investigate the relationship of concussion(s) suffered through childhood and adolescence with completed level of school education and cognitive ability in young adulthood.

METHODS

Educational level and scores on a test of cognitive ability were obtained for a cohort of 130,298 young men processed by the Danish draft board. Of these, 6146 had, at some age from birth onwards, been briefly admitted to hospital with a main discharge diagnosis of concussion. A further 402 had two such concussions and 48 had three or more.

RESULTS

Educational level and cognitive ability test scores were negatively associated with the number of concussions and the age at concussion(s). Most markedly, compared to the 123,684 non-concussed men, those with two or more concussions had lower educational levels (OR = 0.48; 95% CI = 0.26-0.89), as also did those sustaining one concussion between the age of 13 up to the time of testing (OR = 0.47: 0.42-0.52).

CONCLUSIONS

Since concussions do not generally have long-term effects, the results suggest that lower educational level is primarily a risk factor for sustaining a concussion at all ages, but in particular in adolescence more than in childhood and in the case of multiple concussions. It should, however, be recognized that, in some proportion of cases, the educational deficits have probably arisen as a consequence of the persistent symptoms of a lengthy post-concussional syndrome.

Prenatal exposure to alcohol, and gender differences on child mental health at age seven years

BACKGROUND

It remains uncertain whether exposure to lower doses of alcohol is damaging to the developing fetus. The present study aimed to investigate associations for boys and girls between prenatal exposure to binge drinking and lower doses of alcohol in pregnancy, and parent-reported behavioural and emotional development at age seven.

METHODS

This study used data from the Danish National Birth Cohort. Associations between cumulated alcohol exposure and binge drinking from full pregnancy and parent scores on the Strengths and Difficulties Questionnaire (SDQ) measured at age seven were investigated. The SDQ was used as continuous externalising/internalising scores, and as above/below cut-off for the specific scales of hyperactivity/inattention, conduct, emotional and peer problems. Inclusion criteria were information on alcohol exposure from three interviews, SDQ scores at age seven and being born full term (n=37 152).

RESULTS

Controlling for relevant confounders, small positive associations were observed between binge drinking and internalising (relative change in mean: 1.04-1.06), externalising scores (relative change in mean: 1.01-1.07), and conduct scores (OR 1.12 to 1.23) for boys. No associations were observed with lower doses of alcohol.

CONCLUSIONS

Exposure to binge drinking is weakly associated with impaired behavioural and emotional development measured at age seven. Large differences in background characteristics were observed between the groups defined by cumulated alcohol exposure, leaving the interpretations of findings uncertain.

Conscious knowledge influences decision-making differently in substance abusers with and without co-morbid antisocial personality disorder

Decision-making impairment, as measured by the Iowa Gambling Task (IGT), is a consistent finding among individuals with substance use disorder (SUD). We studied how this impairment is influenced by co-morbid antisocial personality disorder (ASPD) and conscious knowledge of the task. Three groups were investigated: SUD individuals without co-morbid ASPD (n = 30), SUD individuals with co-morbid ASPD (n = 16), and healthy controls (n = 17). Both SUD and SUD+ASPD participants had poor overall IGT performance. A block-by-block analysis revealed that SUD participants exhibited slow but steady improvement across the IGT, whereas SUD+ASPD participants exhibited initial normal improvement, but dropped off during the last 40 trials. Conscious knowledge of the task was significantly correlated to performance for controls and SUD participants, but not for SUD+ASPD participants. Our findings suggest that decision-making proceeds differently in SUD and SUD+ASPD individuals due to differences in acquisition and application of conscious knowledge.

Cognitive impairment in the preclinical stage of dementia in FTD-3 CHMP2B mutation carriers: a longitudinal prospective study

OBJECTIVE AND METHODS

A longitudinal study spanning over 8 years and including 17 asymptomatic individuals with CHMP2B mutations was conducted to assess the earliest neuropsychological changes in autosomal dominant neurodegenerative disease frontotemporal dementia (FTD) linked to chromosome 3 (FTD-3). Subjects were assessed with neuropsychological tests in 2002, 2005 and 2010.

RESULTS

Cross-sectional analyses showed that the mutation carriers scored lower on tests of psychomotor speed, working memory, executive functions and verbal memory than a control group consisting of not-at-risk family members and spouses. Longitudinal analyses showed a gradual decline in psychomotor speed, working memory capacity and global executive measures in the group of non-demented mutation carriers that was not found in the control group. In contrast, there were no significant group differences in domain scores on memory or visuospatial functions. On an individual level the cognitive changes over time varied considerably.

CONCLUSION

Subjects with CHMP2B mutation show cognitive changes dominated by executive dysfunctions, years before they fulfil diagnostic criteria of FTD. However, there is great heterogeneity in the individual cognitive trajectories.

Patient compliance in brain injury rehabilitation in relation to awareness and cognitive and physical improvement

The purpose of the present study was to investigate the relationship between patients' compliance and awareness and outcome of brain injury rehabilitation. Subjects were 98 patients who underwent a holistic neuropsychological outpatient rehabilitation programme. Patients had suffered a traumatic brain injury (n = 26), a cerebrovascular accident (n = 58), or another neurological insult (n = 14).

MEASURES

Two staff members, a neuropsychologist and a physiotherapist, retrospectively and separately rated patients' awareness and their compliance. Outcome was measured with the d2 test of concentration, measures of oxygen uptake, strength endurance, running speed, and patients' and relatives' ratings of patients' cognitive, physical, and overall problems on the European Brain Injury Questionnaire (EBIQ). The discrepancy between patients' and relatives' ratings on the EBIQ was incorporated as a second measure of patients' awareness.

RESULTS

The neuropsychologist's compliance ratings were significantly related to measures of insight, improvement of d2 performance accuracy and stability, improvement of oxygen uptake, and reduction of cognitive and overall problems as reported by the patients, while the physiotherapist's compliance ratings were related to measures of insight, improvement of d2 performance speed, improvement of oxygen uptake and strength endurance, and all three EBIQ patient scales.

DISCUSSION

The results suggest a differential relationship between situation-specific compliance and outcome.

The reliability and validity of the Danish Draft Board Cognitive Ability Test: Børge Prien's Prøve

The Danish Draft Board has used the same test for assessing general cognitive ability, the Børge Prien's Prøve (BPP), for over 50 years during which time all men on reaching the age of 18 become liable for conscription. Data from the test has, over the decades, been used in numerous and wide-ranging research studies. Nonetheless, owing to the special circumstances of its administration, some psychometric properties, which are generally assessed for psychological tests, have not previously been investigated for the BPP. First, since the test is only used at the assessment phase, retesting with the BPP occurs only rarely and under exceptional circumstances. Therefore, its Test-Retest reliability has hitherto not been documented. Second, questions have often been raised as to whether the validity of the BPP is undermined by either a lack of motivation and under-performing among some of the men taking the test, being, as they are, compelled to do so, and/or by gradual obsolescence of the test over the decades of its use. We here present findings from three new studies to show that (a) the BPP has a satisfactory Test-Retest reliability, r=0.77, (b) BPP test scores are not positively associated with expressed attitude to being called upon to serve conscription and (c) the correlation between the BPP and a measure of educational level has remained stable (at about 0.5) through the last two decades. Taken together these three findings further support the continuing value of the BPP in research relating to cognitive ability.

Subjective well-being and quality of life following traumatic brain injury in adults: A long-term population-based follow-up

PRIMARY OBJECTIVE

To assess subjective well-being and quality-of-life in nationally representative samples of patients at long intervals following traumatic brain injuries.

METHODS AND PROCEDURES

Patients with either cranial fractures or cerebral lesions were identified in a national computer-based register of hospital admissions and random samples were selected among those who had suffered the injury at 5, 10 or 15 years prior to the follow-up. Postal questionnaires were sent to them covering quality of life, e.g. return to employment, family relations and current subjective well-being in terms of symptomatology, e.g. somatic complaints, cognitive dysfunction. A response rate of 76% was obtained, comprising 114 patients with cranial fracture and 126 with cerebral lesions.

MAIN OUTCOMES AND RESULTS

The group with cerebral lesions had markedly poorer quality of life and subjective well-being than the group with cranial fractures and this did not vary across time. In both groups, the most common symptoms concerned cognition. Among the cerebral lesion group, quality of life outcome was fairly well predicted by severity of injury, but subjective well-being was less well predicted.

CONCLUSIONS

The negative consequences of traumatic cerebral lesions are marked and do not vary at long periods following injury.

Psychosocial consequences of stroke: A long-term population-based follow-up

PRIMARY OBJECTIVE

To investigate psychosocial status among nationally representative groups of stroke patients at long intervals post-stroke.

METHODS AND PROCEDURES

From a Danish national register of hospitalizations, three representative groups of surviving patients were selected who had suffered a stroke 5, 10 and 15 years previously. A follow-up postal questionnaire was sent to them comprising items concerning symptomatology, functioning and social conditions, together with the Nottingham Health Profile (NHP).

MAIN OUTCOMES AND RESULTS

Longer follow-up intervals were associated with younger age at stroke and better functioning at discharge. At follow-up, the majority of patients reported difficulties with attention, memory and emotional control, irrespective of follow-up interval. Return to employment, social relations and leisure activities were affected, but were comparatively better at longer follow-up intervals, as was self-rated functioning and several NHP symptom scales. However, multi-variate analyses suggest that these positive changes with time appear to be mediated by attrition related to age at stroke and discharge functioning rather than time since stroke itself.

CONCLUSIONS

Symptomatology, functioning and social conditions remain affected and perhaps stagnant in long-term survivors of stroke.

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.

Hearing loss in relation to educational attainment and cognitive abilities: A population study

Severe hearing loss among children has often been found to be associated with educational disadvantage and lower-than-average performance on cognitive tests, but less is known about the much more widespread milder levels of hearing loss. In a cohort of 22 162 young Danish men appearing before the draft board, about 75% had normal hearing at 20 dB, and about 20% had mild hearing loss not worse than 25 dB in both ears for all tones less than 3000 Hz, and not worse than an average of 45 dB in both ears for all tones above 2000 Hz. The remaining 5% had more severe hearing loss. The proportions who had continued school education after age 16 years among the three groups were 51%, 42% and 34% respectively and their mean IQs were 101, 98 and 94. The evidence suggests that even mild hearing loss is associated with distinct educational and cognitive disadvantage which itself may result from difficulties in following classroom teaching.

The development of the therapeutic working alliance, patients’ awareness and their compliance during the process of brain injury rehabilitation

PURPOSE

To examine the development and interaction of the therapeutic alliance, patients' compliance and awareness during the process of brain injury rehabilitation and the role of demographic and injury related variables in this process. Subjects were 86 patients who underwent a holistic neuropsychological outpatient rehabilitation programme. Patients had suffered a traumatic brain injury (n = 27), a cerebrovascular accident (n = 49) or another neurological insult (n = 10).

MEASURES

The therapeutic alliance between clients and their primary therapists, clients' awareness and their compliance were rated four times during the 14-week rehabilitation programme. The therapeutic alliance was rated by both clients and therapist using the Working Alliance Inventory (WAI), awareness and compliance were rated by the therapists.

RESULTS

The development of the process measures over time is described in the article. Clients' and therapists' perspectives on their alliance tended to converge over time. Clients' experience of their emotional bond with their therapist added as much to the prediction of clients' awareness as the localization of their brain injury. Clients' awareness was related to their compliance and mediated the impact of the therapeutic alliance on their compliance.

DISCUSSION

A good working alliance is the basis of successful rehabilitative work. The article discusses therapeutic implications of the results.

Subjective outcome of brain injury rehabilitation in relation to the therapeutic working alliance, client compliance and awareness

OBJECTIVE

To investigate the relationship between working alliance, compliance, awareness and subjective outcome of brain injury rehabilitation. Subjects were 86 patients who were clients in an holistic neuropsychological outpatient rehabilitation programme. They had suffered a traumatic brain injury (n = 27), a cerebrovascular accident (n = 49) or some other neurological insult (n = 10).

MEASURES

The therapeutic alliance, clients' awareness and their compliance were rated four times during the 14-week rehabilitation programme. The therapeutic alliance was rated by both clients and therapist using the Working Alliance Inventory (WAI), awareness and compliance were rated by the therapists. Clients completed the European Brain Injury Questionnaire (EBIQ) at programme start and end. Clients and therapists rated the overall success of their collaboration at programme end.

RESULTS

Clients' experience of a good emotional bond between themselves and therapists in mid-therapy was predictive for the reduction of clients' report of depressive symptoms on the EBIQ depression sub-scale (R = 0.68, n = 43, p < 0.001). Good compliance early in the programme was predictive of changes on the EBIQ. Improvement of awareness was related to the amplification of depressive symptoms (r = -0.27, n = 56, p < 0.05).

CONCLUSIONS

Brain injury rehabilitation should be seen as a dynamic process that develops between clients and therapists. Future research should further investigate the relationship between process and outcome and how the therapeutic process can be optimized.

The relationship between clients’ cognitive functioning and the therapeutic working alliance in post-acute brain injury rehabilitation

OBJECTIVE

To examine the impact of brain-injured patients' cognitive abilities on their working alliance (WA) with their therapist in post-acute rehabilitation.

DESIGN

Cognitive tests were administered to brain-injured individuals at the beginning of post-acute, holistic brain-injury rehabilitation. Clients as well as their primary therapists rated their mutual WA at four time points throughout a 14-week rehabilitation programme. Subjects consisted of 86 clients as well as their primary therapists. Clients had suffered a traumatic brain injury (n = 27), a cerebrovascular accident (n = 49) or another neurological insult (n = 10).

MEASURES

(1) Neuropsychological tests of attention, memory and higher cognitive functions; (2) the Working Alliance Inventory, client and therapist short form.

RESULTS

Overall, the relationships between cognitive tests and WA ratings were weak. The tests of attention, memory and higher cortical functions were differentially related to clients' and therapists' view of their mutual WA at the different stages of their collaborative work.

DISCUSSION AND CONCLUSION

Clients' cognitive profile affects clients' and therapists' view of their WA in different ways. The weakness of the correlations between cognitive tests and WA ratings may indicate that a good WA is achievable also with clients with severe cognitive difficulties.

Alleviation of carer strain during the use of the NeuroPage device by people with acquired brain injury

BACKGROUND

Previous studies have demonstrated the efficacy of a paging system, NeuroPage (Cambridgeshire Primary Care Trust Corporation, Fulbourn, Cambridgeshire, UK), in compensating for memory and planning dysfunctions in people with acquired brain injury (ABI; mainly stroke or traumatic brain injury). In this study, the degree to which this efficacy is accompanied by a reduced experience of strain among carers of patients with ABI was investigated.

METHODS

Carers of 99 people with ABI completed a questionnaire concerning strain resulting from caring for the injured individual. The questionnaire was completed at the following three time points: before the use of NeuroPage, at the end of a 7-week period of use, and, for one subgroup, a further 7 weeks after withdrawal of NeuroPage.

RESULTS

There were significant reductions in strain reported by carers following the 7-week period of NeuroPage use (Cohen's d = 0.3-0.4). This finding persisted when the carer was a spouse or a parent. The reduced strain among carers continued even after withdrawal of NeuroPage.

CONCLUSION

The efficacy of the NeuroPage paging system for people with ABI appears to result in reduced strain for their carers.

The European Brain Injury Questionnaire (EBIQ) as a reliable outcome measure for use with people with brain injury

PRIMARY PURPOSE

There is a need to develop reliable outcome measures to determine well-being after brain injury. In 1997, Teasdale et al. published the European Brain Injury Questionnaire (EBIQ), a self-report and relative-report measure of the subjective experience of cognitive, emotional and social difficulties experienced by people with brain injury. It is now used in several rehabilitation centres as an outcome measure, but its test-re-test reliability has yet not been determined. The primary purpose of the present study is to establish this degree of reliability.

RESEARCH DESIGN

The EBIQ was administered twice within an approximately 1-month period to 50 people with brain injury, to 20 relatives of people with brain injury and to 51 normal controls.

RESULTS

The results showed significant and satisfactory test-re-test reliabilities for all three groups across all nine EBIQ scales (r = 0.55-0.90).

CONCLUSION

It is concluded that the EBIQ is a clinically reliable measure to determine the subjective well-being of people with brain injury and to assess change of subjective concerns over time.

Working alliance and patient compliance in brain injury rehabilitation and their relation to psychosocial outcome

Employment and physical activity at follow up of 98 patients who underwent a holistic neuropsychological outpatient rehabilitation programme were examined in relation to therapeutic process factors. The patients had suffered a traumatic brain injury (n = 26), a cerebrovascular accident (n = 58) or another neurological insult (n = 14). Two staff members, a neuropsychologist and a physiotherapist, retrospectively rated patients' compliance with the therapeutic regime and their working alliances. They completed the ratings separately, but had some degree of common knowledge about the patients. While the compliance ratings were closely associated, working alliance ratings differed between the raters. The working alliance ratings were predictive of employment, but not physical activity. Both compliance ratings predicted physical training, but only the neuropsychologist's compliance rating was associated with follow-up employment. Post-hoc analysis showed that high compliance ratings given by the physiotherapist were also a predictor of employment. Overall, there was a tendency for the neuropsychologist's ratings to be more closely associated with employment than the physiotherapist's ratings. These results indicate that employment and physical activity are differentially predictable from different process measures rated from different professional perspectives.

Neuropsychological dysfunction following repeat concussions in jockeys

A second concussion risks permanent cognitive dysfunction

Genetic and environmental influences on the relation between parental social class and mortality

BACKGROUND

Genetic and maternal prenatal environmental factors as well as the post-natal rearing environment may contribute to the association between childhood socioeconomic circumstances and later mortality. In order to disentangle these influences, we studied all-cause and cause-specific mortality in a cohort of adoptees, in whom we estimated the effects of their biological and adoptive fathers' social classes as indicators of the genetic and/or prenatal environmental factors and the post-natal environment, respectively.

METHODS

In all 12 608 children born 1924-47 in Denmark who were placed early in life with adoptive parents were followed up for causes of death until 2000. Hazard ratios for paternal social class retrieved from adoption records were estimated using Cox regression models.

RESULTS

Adoptees with biological fathers from higher social classes had a lower rate of mortality after their fifth decade of life, mainly due to a lower risk of cardiovascular, infectious, and respiratory diseases. Adoptive father's social class showed no clear relation with adoptee's mortality risk. The risk estimates for paternal social class were slightly attenuated after adjustment for adoptee's adult social class, which as expected was inversely related to mortality from both natural and external causes.

CONCLUSION

Genetic and/or prenatal environmental factors contribute to the development of the relation of paternal social class to mortality from natural causes later in adult life independently of the effect of own social class, whereas there is no evidence for such long-term effect of the rearing environment.

A population-based study of survival and discharge status for survivors after head injury

OBJECTIVES

Creation of a basis for the planning of rehabilitation after head injury in Denmark.

MATERIALS AND METHODS

Patients with cranial fractures or traumatic cerebral lesions occurring in Denmark in 1979-93 were identified by computerized searches in the national hospital register. Kaplan-Meier survival functions were calculated for these two categories. Hospital records for a random sample of 389 survivors in 1997 after cranial fracture, acute brain lesion or chronical subdural haematoma, which occurred in 1982, 1987 and 1992 in patients aged 15 years or more at injury, were reviewed. Survivors were characterized by age, gender, place and severity of injury, as well as neurophysical, speech and mental deficits at discharge from hospital.

RESULTS

Acute/subacute mortality of hospitalized patients was 27% for cerebral lesions and 4% after cranial fracture. As attrition by death outweighed the decreasing incidence with time, the point prevalence of survivors in 1997 after brain lesions occurring in 1982, 1987 or 1992 was nearly the same, averaging 8.4 per 100 000 of the population above age 14. Half of them were severe, as defined by initial Glasgow Coma Score < 9 for more than 6 h. There was no tendency with time of injury with regard to percentage occurrence of neurophysical, speech or mental deficits at discharge. The calculated number of candidates for rehabilitation of personal activities of daily life briefly after injury was 9.8 per 100 000 with cerebral lesion and 1.2 per 100 000 with cranial fracture. The severest 1.5 per 100 000 per year were candidates for early intensive centralized rehabilitation in special centres. Five years after injury, < 0.13 per 100 000 population survived in the vegetative state.

CONCLUSION

In this population-based study, survival after cranial fracture and cerebral lesion was described quantitatively through Kaplan-Meier survival distributions. Besides, patterns of severity, neurophysical and mental sequelae among survivors 5, 10 and 15 years post-injury were described. It was shown by examples how the study has been useful already for the planning of rehabilitation according to a national strategy from 1997 in Denmark. Besides, the results may serve as a reference for comparison with future studies.

Psychosocial outcome following traumatic brain injury in adults: a long-term population-based follow-up

PRIMARY OBJECTIVE

On a national basis to conduct a 5, 10 and 15 year follow-up study of representative samples of survivors after traumatic brain injury (TBI) and to identify factors of importance for long-term survival and life satisfaction after TBI occurring in 1982, 1987 or 1992.

RESEARCH DESIGN

Epidemiological, register-based questionnaire survey.

MAIN OUTCOMES, RESULT AND CONCLUSIONS

Out of 389 survivors randomly chosen from a national complete hospital register, 173 had suffered a cranial fracture, 186 a cerebral lesion (brain contusion or traumatic haemorrhage) and 30 patients a chronic subdural haematoma. Out of 337 survivors found eligible for a questionnaire, 76% responded. Among the data registered according to the above mentioned areas, the main findings were that 23-31% of the cerebral lesion responders were unable to maintain earlier work/education at pre-injury level, against up to 14% of cranial fracture patients. Significantly more cerebral lesion patients than cranial fracture patients found emotional control more difficult, as well as increased difficulties with memory and concentration, maintenance of leisure time interests and general life satisfaction. In the long run, an important factor influencing survival among cerebral lesion patients seemed to be whether relations with family and friends could be maintained at the pre-injury level.

Cognitive dysfunction in young men following head injury in childhood and adolescence: a population study

OBJECTIVES

To examine the prevalence of cognitive dysfunction among young men who had suffered a head injury during childhood or adolescence, in particular focusing upon the effects of age and the severity of the injury.

METHODS

By cross linkage of Danish national registers for hospital admissions and the draft board, 3091 young men were identified who had been injured before age 18 and tested at age 18 or shortly thereafter: 970 had suffered a single concussion and were in hospital for one day only; 521 had two concussions at separate times and were in hospital for one day only on each occasion; 961 had a cranial fracture; and 639 had a cerebral lesion. For all of these, scores on the draft board's cognitive screening test were obtained, dichotomised as dysfunctional or non-dysfunctional. Prevalences of dysfunctional scores were compared with population base rates (about 20% of all Danish men appearing before the draft board had a score classified as dysfunctional).

RESULTS

For young men who had suffered a single concussion, cranial fracture, or cerebral lesion before 12 years of age, resulting in less than 12 days of hospital admission (n = 376), rates of cognitive dysfunction did not exceed those in the general population (odds ratios < 1.4, NS), but the odds ratios became significant and > 1.4 where the injury occurred after age 11. For those with a cerebral lesion resulting in over 11 days of hospital admission (n = 263), all odds ratios were significant and >or= 2.0, irrespective of age at injury. For cases of two concussions, all odds ratios were > 1.4 but were not significant for all age groupings.

CONCLUSIONS

For milder forms of single head injury before age 12 there is no evidence of enduring cognitive dysfunction. The apparent effect at later ages may reflect predisposing psychosocial factors. For more serious injury, and for cases with two concussions, the effect is marked and not clearly related to age. For the former, this suggests enduring neurological effects of the injury; for the latter, where the effect is unrelated to time between injuries, predisposing factors may again play a role.

Disability pensions in relation to stroke: a population study

PRIMARY OBJECTIVE

This study aimed to establish prevalence levels of disability pensions among stroke patients within a national population.

RESEARCH DESIGN

From a Danish National register of hospitalizations, 72 673 patients were identified who had a discharge diagnosis of stroke between the years 1979-1993 inclusive and were of pensionable age during that period. These patients were then screened in registers for death during the period 1979-1993 and for the award of disability pensions between the years 1979-1995. A total of 19476 (27%) patients had received a pension at some level.

MAIN OUTCOMES AND RESULTS

Being in possession of a disability pension prior to stroke (n = 8565, 12%), rarely at the highest level, was not associated with elevated risk for stroke, or with elevated stroke mortality. It was, however, associated with a greater mortality subsequent to stroke. Disability pensions awarded following stroke (n = 10564, 15%), often at the highest level, were awarded equally to males and females in all age groups, but most commonly (ca 50%) at age 50-59. Disability pensions awards were also strongly related to duration of hospitalization. Among stroke sufferers hospitalized for over 90 days, the proportion ultimately awarded a disability pension rises to over 80%.

CONCLUSIONS

The results show high levels of disability pensions awards to relatively young stroke patients probably reflecting pessimism concerning ability to return to employment in such patients. More recent development of stroke units and post-acute rehabilitation programmes may justify greater optimism.

Traumatic brain injury in Denmark 1979-1996. A national study of incidence and mortality

In order to describe and analyse the development of the incidence of traumatic brain injury (TBI) in Denmark for different age groups of the two genders from 1979 through 1993 (for fatal injuries through 1996), a computerised search corresponding to diagnoses ICD 8th ed., 800, 801, 803, 850-854 from 1979 through 1993 was carried through in the national hospital register. Each person was counted only once, according to the most serious injury during the study period. For fatal cases, the search was extended till 1996. From 1979-1981 to 1991-1993, the total age-adjusted incidence of persons hospitalised under diagnoses ICD 800, 801, 803, 850-854 decreased 41% from 265 to 157 per 100,000 of the population per year. Decreases were 42% for ICD 850, brain concussion, 56% for ICD 800, 801, 803, cranial fractures, and 16% for ICD 851 854, structural brain injury. The percentage of cases with ICD 851-854 increased from 8.4 to 11.7% of the total. From 1979-1981 to 1985-1987 there was a 2% decrease in fatal TBI in and outside hospital (from 14.68 to 14.35 per 100,000), against a total 27% decrease to 10.67 in 1994-1996. For diagnoses ICD 851-854 and for fatal cases, significantly accelerating decreases from 1985-1987 were found only for the younger age groups. Consequently, in the period from 1979 to 1993, the mean age at injury increased by 10 years for persons hospitalised under diagnoses ICD 851-854. Decreases may be explained partly by changing admission and other hospital practices, and partly by the effect of comprehensive national preventive programs launched at the middle of the study period, the effect of which seemed to vary by age group and gender.

Suicide after a stroke: a population study

STUDY OBJECTIVE

To establish whether there are increased rates of suicide after a stroke and the degree to which any increase is related to gender, age at stroke, diagnosis, duration of hospitalisation, and time since stroke.

DESIGN

Cross linkage of national registers for hospitalisations and causes of death.

SETTING

The population of Denmark, 1979-1993.

PATIENTS

A study cohort was defined comprising all 114 098 stroke patients discharged alive from hospital during the period 1979-1993. These patients were then screened in a register of causes of death over the same time period, and 359 cases of suicide were identified.

MAIN RESULTS

Annual incidence rates, both observed and expected, together with standardised mortality ratios (SMR) were computed based on annual population and suicide statistics, stratified by age and gender. The overall annual incidence rate of suicide in the cohort was 83 per 100 000 per year compared with an expected figure of 45 (difference = 38, 95% CI = 27, 49). Correspondingly, SMR were increased for stroke patients. Across all age bands the SMR for mens was 1.88 (95%CI 1.66, 2.13) and for women 1.78 (1.48, 2.14). SMR were greatest (2.85; 2.17, 3.76) for patients under 50 years of age group and were least for patients 80 years or older (1.3; 0.95, 1.79). There was no clear relation to stroke diagnosis. Suicides were negatively related to duration of hospitalisation, being lowest for those hospitalised for more than three months (0.88; 0.65, 1.19) and highest for those hospitalised for less than two weeks (2.32; 1.92, 2.80). Survival analysis suggested that the risk for suicide is greatest up to about five years after a stroke.

CONCLUSIONS

Stroke patients are at an approximately doubled risk for suicide. This risk is greater among younger patients and among patients hospitalised for a relatively shorter time. The risk appears to decline with time after a stroke, being greatest within the first five years.

Suicide after traumatic brain injury: a population study

OBJECTIVES

To determine the rates of suicide among patients who have had a traumatic brain injury.

METHODS

From a Danish population register of admissions to hospital covering the years 1979-93 patients were selected who had had either a concussion (n=126 114), a cranial fracture (n=7560), or a cerebral contusion or traumatic intracranial haemorrhage (n=11 766). All cases of deaths by the end of the study period were identified.

RESULTS

In the three diagnostic groups there had been 750 (0.59%), 46 (0.61%), and 99 (0.84%) cases of suicide respectively. Standardised mortality ratios, stratified by sex and age, showed that the incidence of suicide among the three diagnostic groups was increased relative to the general population (3.0, 2.7, and 4.1 respectively). In all diagnosis groups the ratios were higher for females than for males, and lower for patients injured before the age of 21 or after the age of 60. The presence of a codiagnosis relating to substance misuse was associated with increased suicide rates in all diagnosis groups. There was a tendency, among patients with cerebral contusions or traumatic intracranial haemorrhages, for suicide risk to increase with duration of stay in hospital. Cox regression analyses for proportional hazards confirmed that there was a significantly greater risk of suicide among patients with cerebral contusions or traumatic intracranial haemorrhages than among patients with concussion or cranial fractures (hazard ratios=1.42 and 1.50 respectively). There was, however, no evidence of a specific risk period for suicide after injury.

CONCLUSION

The increased risk of suicide among patients who had a mild traumatic brain injury may result from concomitant risk factors such as psychiatric conditions and psychosocial disadvantage. The greater risk among the more serious cases implicates additionally the physical, psychological, and social consequences of the injuries as directly contributing to the suicides.

Cognitive abilities in left-handers: writing posture revisited

Among 1848 young men appearing before the Danish draft board, 232 (13%) were left-handed. Of these, 118 (51%) used an inverted, or hook-like, writing posture, 49 (21%) used a non-inverted posture and the remaining 65 (28%) could not be categorized. There were no differences between left- and right-handers on a battery of four cognitive tests. However, inverted left-handers performed significantly or near-significantly better than the non-inverted left-handers on two of the four tests and significantly better on the total score for the test battery. These results support the contention that the inverted posture is adaptive for left-handers and suggest that it may be more likely to be adopted by those with better cognitive abilities. Our findings conflict with earlier reports from two decades ago, however, and the association may therefore be socially and culturally dependent.

Disability pensions in relation to traumatic brain injury: a population study

From a Danish national register of hospitalizations, all patients were identified who had a discharge diagnosis of traumatic brain injury between the years 1979-1993 inclusive, at ages 18-66 years inclusive. These were classified as having suffered either a concussion (n = 74,398), a cranial fracture (n = 4,452) or a cerebral contusion (n = 8,141). Patients in each of these groups were then checked in annual registers of disability pension awards between 1979-1995. Disability pensions had been awarded to 16% of the concussion group, 18% of the fracture group, and 33% of the contusion group. Date of application, grounds for the application, and the pension level awarded were noted. Analysis of the date of application for the disability pension revealed that in all groups a high proportion of the pension applications had been made prior to the injury. Among the concussion group, the pension award appeared to be independent of the injury itself. Rather, being awarded a disability pension appeared to be related to conditions which themselves are risk factors for a traumatic brain injury, e.g. chronic skeletomuscular disease and psychiatric disorders including alcoholism. Comparison with population statistics revealed that the relative risk of being assigned a low or intermediate disability pension is markedly elevated among the concussion group, especially at younger ages and among males. For the fracture and contusion groups, a clear post-injury elevation in rate was detectable, especially for highest level pensions.

Traumatic brain injury in children in Denmark: a national 15-year study

Demographic trends are reported concerning three types of traumatic brain injury (concussions, cranial fractures, and intracranial contusions/haemorrhages) among children in Denmark of ages up to and including 14 years, for a fifteen year period from 1979 through 1993. The data were derived from a national computer-based hospitalization register and include 49,594 children, of whom 60% were boys and 89% had suffered a concussion. Virtually all injuries were the result of accidents. A major finding was that there has been a general decline in the incidence of traumatic brain injuries, especially for boys from 5 to 14 years old, suggesting a degree of success in preventive measures, particularly regarding road safety. The incidence of fatal cases of intracranial contusions/haemorrhages approximately halved over the 15 year period. However, as a proportion of all diagnosed cases, mortality from intracranial contusions/haemorrhages remained fairly constant at about 22%, perhaps because there have been no markedly successful innovations in acute care. Among children surviving a intracranial contusions/haemorrhages, rather considerable numbers were found to have been awarded disability pension at ages under 30.

Duration of cognitive dysfunction after concussion, and cognitive dysfunction as a risk factor: a population study of young men

OBJECTIVES

To establish how long cognitive dysfunction lasts after concussion, and the extent to which it may be a predisposing risk factor for concussion, by examining the prevalence of cognitive dysfunction among young men who have sustained concussion.

DESIGN

Observational study.

SETTING

Denmark.

SUBJECTS

1220 young men who had been admitted to hospital for concussion between the ages of 16 and 24 (identified in a national register of admissions) and who had also been cognitively tested by the Danish conscription draft board.

MAIN OUTCOME MEASURE

Score on the draft board's cognitive screening test, dichotomised as dysfunctional or non-dysfunctional (20.4% of the general population of Danish men appearing before the draft board had a dysfunctional score).

RESULTS

700 of the 1220 men had been tested after sustaining concussion; 520 had been tested before concussion. Four (50%) of the eight men who were tested less than seven days after the injury had a dysfunctional score. Among groups of the remaining 692 men who were tested at later time points after injury, the rates were only marginally raised (range 21.4% to 26.5%) above the population level. Among men tested before injury, the rate of dysfunctional scores was higher (30.4% (158/520)). Apart from suggesting cognitive dysfunction as a risk factor for concussion, this higher proportion seems to relate to the fact that they were typically injured as young adults, whereas those men who were tested after concussion had more often been injured as adolescents. The relative risk for concussion in the presence of cognitive dysfunction is estimated to be 1.57 (95% confidence interval 1.32 to 1.86).

CONCLUSIONS

Cognitive dysfunction is not only a short term consequence of concussion but also a predisposing risk factor for concussion, more so for young adults than for adolescents.

Subjective experience in brain-injured patients and their close relatives: a European Brain Injury Questionnaire study

Results are reported from an international project the aim of which has been to develop and validate a wide-ranging questionnaire suitable for administration to brain-injured patients and their relatives. A self-report questionnaire concerning subjective experience of cognitive, emotional and social difficulties (The European Brain Injury Questionnaire, EBIQ) was administered to a group of 905 brain-injured patients, and close relatives to these competed a parallel version of the questionnaire concerning the brain-injured person. The sample was drawn from seven European countries together with Brazil. The same questionnaire was also administered to a group of 203-non-brain-injured controls, similarly in self-report and relative-report versions. Scales relating to eight specific areas of functioning, together with a global scale, are derived from the questionnaire and their internal reliability was estimated in the present data. Analyses of the 63 items of the questionnaire showed consistently greater levels of problems for the brain-injured group, especially as indicated by relatives. This pattern was substantially replicated among the nine scales. The scales discriminated well between stroke patients and those who had suffered a traumatic brain injury. There was also a tendency for reported problems to be greater for patients who were surveyed later post-injury (> or = 19 months) rather than earlier. Comparison of sets of controls derived from two countries (France and Brazil) showed small but important differences. It is concluded that the questionnaire has an acceptable reliability and validity, but that it will be necessary to obtain culturally relevant non-brain-injured control data when employing it in different countries.

Psychopathological symptomatology in brain-injured patients before and after a rehabilitation program

The Symptom Checklist-90 revised (SCL-90-R) was used to evaluate subjective experience of psychopathological symptomatology in 30 patients before and after an intensive four-month neuropsychological rehabilitation program and again one year after completion of the program. The patients were all adults and had suffered acute brain injury as a result of head injury (37%), cerebro vascular accident (37%), anoxia (16%) or other causes (10%). Most had entered the program within two years after injury and at that time they showed slight to moderate elevation on all ten scales of the SCL-90-R. At program completion eight of the scales showed significant or near significant reductions. There were only small and non-significant changes in the scales between program completion and one year follow-up. Among the individual items of the SCL-90-R, the most common complaints related to cognitive difficulties and depression. The same pattern of sustained improvement was largely found for these items. Overall the results suggest, first, that the subjectively perceived distress in the brain-injured patient is diminished by the rehabilitation program, and second, that this reduction sustained at least up to one year following the completion of the program.

Thirty-year secular trends in the cognitive abilities of Danish male school-leavers at a high educational level

A nationally representative sample of Danish males finishing school in 1989, or shortly before, with a studentereksamen (the highest qualification in the Danish school system) was found to score generally lower on a battery of four cognitive tests than a comparable sample of Danish males who had taken the same tests shortly after finishing school in the late 1950s or early 1960s. This decline appears attributable to the increasing proportions of students who obtain the studentereksamen and is quite compatible with an overall increase in test scores, also found in our data, for the general population over the same time period. For those who obtain the studentereksamen, the decline has been most marked in a test of verbal analogies. It has been smaller for tests of logical and spatial reasoning, and scores on a test of numerical ability have actually improved over the 30 years. This differential pattern may be the result of both student changes and curricular changes within Danish schools.