Preben Bo Mortensen

Psychiatric illness and risk factors for suicide in Denmark.

BACKGROUNDnSeveral risk factors for suicide have been identified. We assessed the relative risks and population attributable risks of suicide associated with various socioeconomic factors and with previous mental illness that necessitated hospital admission. Our aim was to assist in the choice of potential strategies for preventing suicide in the general population.nnnMETHODSnWe did a population-based nested case-control study based on register data. Data were collected on a random 5% sample of the Danish population aged 16-78 years during a 15-year period (1980-94) and analysed with conditional logistic regression.nnnFINDINGSn811 cases of suicide were found and 79871 controls were chosen in this population. Unemployment, low income, being single, and a history of mental illness necessitating hospital admission were associated with increased risk of suicide. However, in the multivariate analysis, the strongest risk factor was mental illness necessitating hospital admission; risk of suicide was especially high during admission (relative risk 62.6 [95% CI 41.1-95.4]) and during the year after discharge (6.51 [5.03-8.44]). The effect of socioeconomic variables decreased after adjustment for history of mental illness. The population attributable risk associated with mental illness necessitating admission to hospital was 44.6% (43.6-45.5); the attributable risks associated with the other factors were 3.0% (1.4-6.6) for unemployment and 10.3% (6.13-16.9) for being single.nnnINTERPRETATIONnSuicide prevention aimed at patients who are admitted to hospital with mental disorders and improved detection and treatment of mental disorders in the general population may be the most efficient strategy to decrease risk of suicide. Reports of high relative risk and attributable risk associated with unemployment and other socioeconomic risk factors may be confounded and overestimated owing to the lack of adjustment for the association with mental disorders.

Validity of Dementia Diagnoses in the Danish Hospital Registers

Background:The validity of dementia diagnoses in the Danish nationwide hospital registers was evaluated to determine the value of these registers in epidemiological research about dementia. Methods: Two hundred patients were randomly selected from 4,682 patients registered for the first time with a dementia diagnosis in the last 6 months of 2003. The patients’ medical journals were reviewed to evaluate if they fulfilled ICD-10 and/or DSM-IV criteria for dementia and specific dementia subtypes. The patients who were still alive in 2006 were invited to an interview. Results: One hundred and ninety-seven journals were available for review and 51 patients were interviewed. A registered diagnosis of dementia was found to be correct in 169 (85.8%) cases. Regarding dementia subtypes, the degree of agreement between the registers and the results of the validating process was low with a kappa of 0.36 (95% CI 0.24–0.48). Conclusion: The validity of dementia syndrome in the Danish hospital registers was high and allows for epidemiological studies about dementia. Alzheimer’s disease, although underregistered, also had a good validity once the diagnosis was registered. In general, other ICD-10 dementia subtypes in the registers had a low validity and are less suitable for epidemiological research.

Specific characteristics of suicide in China

Objective: The aims of this paper are (i) to describe the specific characteristics of suicide in China and compare it with that in a western country, Denmark; and (ii) to discuss the accuracy of suicide data and the possible explanations for suicide behaviour in China.

Infantile Autism and Associated Autosomal Chromosome Abnormalities: A Register-based Study and a Literature Survey

Infantile autism is a heterogenous disorder with unknown aetiology. Evidence from the relatively few family and twin studies suggests a genetic component. Co-occurrence or cosegregation between infantile autism and chromosomal abnormalities may identify candidate regions, which could be tested in linkage or association studies. The purpose of this study was to use the Danish Cytogenetic Central Register in order to detect autosomal chromosome abnormalities associated with infantile autism, and to review the literature for cases of autism associated with autosomal chromosome abnormalities to identify candidate chromosomal regions. The register-based study identified possible candidate regions on chromosome 7q21 and 10q21.2, which have not previously been reported. A few interesting candidate regions, 15q11-13, 16q23, and 17p11.2 were found in the literature survey.

A population-based register study of the association between schizophrenia and rheumatoid arthritis

The authors investigated the association between schizophrenia and rheumatoid arthritis. The design is a population-based case-control and follow-up study. The cases were 20495 patients admitted for schizophrenia and registered in the Danish Psychiatric Case Register. A total of 204912 persons matched on age and gender and chosen from the general population served as controls. Admissions for rheumatoid arthritis and other non-autoimmune, musculoskeletal disorders were checked in the Danish National Patient Register. Odds ratios and relative risks were estimated by the Mantel-Haenszel estimator and Poisson regression. The same analyses were carried out for 10242 patients with bipolar affective disorder and 102420 controls for comparison. Individuals with schizophrenia had a reduced risk for being admitted with rheumatoid arthritis [odds ratio 0.44 (CI 0.24-0.81)] in the case-control study. A similar result was found in the follow-up study, but the incidence of the degenerative disorders in the musculoskeletal system was equally significantly lower in both studies. The incidence of rheumatoid arthritis among the bipolar patients was the same as in the control population. The negative association between schizophrenia and rheumatoid arthritis may thus be the result of ascertainment bias and selection due to under reporting and treatment of the medical illness. Clinicians are reminded of the difficulties in detecting medical illness among individuals with schizophrenia.

Obstetric complications in women with schizophrenia

It is not known whether schizophrenic women have increased incidence of complications during pregnancy and delivery. Data from the Danish Medical Birth Register were used to compare 2212 births to 1537 schizophrenic women in Denmark with a random sample of all deliveries in Denmark during 1973-1993 (122931 births to 72742 women). The schizophrenic women had fewer antenatal care visits. They were at lower risk of pre-eclampsia, but tended to have lower Apgar scores. There were no other differences in the incidence of specific complications such as placenta previa, placental abruption, and abnormal fetal presentation. Schizophrenic women were at increased risk of interventions such as Cesarean section, vaginal assisted delivery, amniotomy, and pharmacological stimulation of labor. There were no important differences between the deliveries to schizophrenic women who gave birth before and after their first admission to a psychiatric department. These results show no evidence that schizophrenic women have a greater frequency of specific obstetric complications than non-schizophrenic women. Nevertheless, they are at increased risk for interventions during delivery.

Medical Disorders Among Inpatients with Autism in Denmark According to ICD-8: A Nationwide Register-Based Study

Possible associations between autism and specific medical disorders have been suggested, and this could be of relevance in the clinical examination and treatment of patients and may help to identify factors involved in the etiology or pathophysiology of autism. Two population-based Danish registers were used to investigate the occurrence of medical disorders in patients with autism according to ICD-8 and in a matched control sample. A total of 29 of the 244 patients (11.9%) diagnosed with autism had one or more medical disorders. In contrast to previous studies, we did not find an increased occurrence of almost any medical disorders. A highly significant increased frequency of congenital malformations was found, which may indicate abnormalities in embryogenesis in the etiology of autism.

Higher socio-economic status of parents may increase risk for bipolar disorder in the offspring

BACKGROUNDnThere are conflicting data regarding the socio-economic risk factors for bipolar disorders. The aim of the present study was to explore the association between the socio-economic status of an individual or the parent and the risk for bipolar disorder.nnnMETHODnTwo Danish registers were merged. From the data source, we extracted those born in 1960 or later, and those with a first-ever admission to, or contact with, Danish psychiatric facilities during 1981-1998 with a diagnosis of bipolar disorder. Fifty time-matched controls per case were chosen by the incidence-density sampling method. Effects of marital status, occupation, education, income, and wealth, of both subjects and the parents, were estimated using conditional logistic regression.nnnRESULTSnA total of 947 cases were matched to 47 350 controls. Those at high risk of bipolar disorders were: single subjects, those in receipt of social assistance, pension or sickness payments, unemployed, subjects with a shorter educational history, and subjects with lower income. Conversely, parental higher education and higher level of paternal wealth were associated with increased risk. These associations remained significant after adjustment for gender, family history of psychiatric diagnoses, and other socio-economic variables, and are unlikely to be explained by known biases.nnnCONCLUSIONSnThe associations of lower socio-economic indices of subjects may be explained as a consequence of the disease. The association of higher socio-economic indices of parents may be explained by socio-economic achievement in the family of origin.

A possible association between the genetic predisposition for dizygotic twinning and schizophrenia

BACKGROUNDnA previous study demonstrated a 40% higher rate of schizophrenia in dizygotic twins than in the general population. The aim of the present study is to evaluate whether genes influencing the rate of dizygotic twinning and genes of importance for developing schizophrenia can be associated.nnnMETHODnThrough record linkage between The Danish Twin Register, The Danish Psychiatric Central Register, and The Danish Civil Registration System, the rate of schizophrenia in singleton siblings of dizygotic and monozygotic twins was compared with the rate in siblings of singletons.nnnRESULTSnThe rate of first admission to hospital for schizophrenia in siblings of dizygotic twins was 35% greater than the rate in siblings of singletons. The result was statistically significant (p = 0.04). The rate in siblings of monozygotic twins was not increased.nnnCONCLUSIONnThe results are in accordance with a theory of a linkage between genes influencing the rate of dizygotic twinning and genes influencing the threshold for developing schizophrenia.