Bidirectionality of antiseizure and antipsychotic treatment: A population-based study.

PURPOSE: To study the prevalence and directionality of comorbid epilepsy and psychosis in Norway. METHODS: The Norwegian Prescription Database (NorPD) provided individual-based information on all antiseizure medications (ASMs) and antipsychotic drugs (APDs) dispensed during 2004-2017. Subjects were ≥18 years of age at the end of the study period. Diagnosis-specific reimbursement codes from the 10th revision of the International Classification of Diseases/2nd edition of the International Classification of Primary Care (ICD-10/ICPC-2) combined with ATC codes were used as indicators of diagnosis. Subjects had collected ASMs for epilepsy or APDs for psychosis at least four times, at least once issued with an ICD-10 code from the specialist healthcare service. Directionality was analyzed in subjects receiving both treatments. To reduce prevalent comorbidity bias, we employed a four-year comorbidity-free period (2004-2007). The use of specific ASMs and APDs was analyzed. RESULTS: A total of 31,289 subjects had collected an ASM for epilepsy at least four times, 28,889 an APD for psychosis. Both the prevalence of treatment for epilepsy and of treatment for psychosis was 0.8%. Further, 891 subjects had been treated for both conditions; 2.8% with epilepsy had been treated for psychosis, and 3.1% with psychosis had been treated for epilepsy. Among 558 subjects included in the analyses of directionality, 56% had collected the first APD before an ASM, whereas 41% had collected an ASM first. During the last year prior to comorbidity onset, levetiracetam, topiramate, or zonisamide had been used for epilepsy by approximately 40%, whereas olanzapine and quetiapine were most used in patients with psychosis, and clozapine in 13%. CONCLUSION: The proportion of patients with prior antipsychotic treatment at onset of epilepsy is higher than previously acknowledged, as demonstrated in this nation-wide study. Apart from a shared neurobiological susceptibility, the bidirectionality of epilepsy and psychosis may be influenced by various environmental factors, including the interaction of pharmacodynamic effects. APDs may facilitate seizures; ASMs may induce psychiatric symptoms. In patients with combined treatment, these potential drug effects should receive ample attention, along with the psychosocial consequences of the disorders. A prudent multi-professional approach is required.

Influenza vaccination and risk for cardiovascular events: a nationwide self-controlled case series study.

BACKGROUND: US and European guidelines diverge on whether to vaccinate adults who are not at high risk for cardiovascular events against influenza. Here, we investigated the associations between influenza vaccination and risk for acute myocardial infarction, stroke and pulmonary embolism during the 2009 pandemic in Norway, when vaccination was recommended to all adults. METHODS: Using national registers, we studied all vaccinated Norwegian individuals who suffered AMI, stroke, or pulmonary embolism from May 1, 2009 through September 30, 2010. We defined higher-risk individuals as those using anti-diabetic, anti-obesity, anti-thrombotic, pulmonary or cardiovascular medications (i.e. individuals to whom vaccination was routinely recommended); all other individuals were regarded as having lower-risk. We estimated incidence rate ratios with 95% CI using conditional Poisson regression in the pre-defined risk periods up to 180 days following vaccination compared to an unexposed time-period, with adjustment for season or daily temperature. RESULTS: Overall, we observed lower risk for cardiovascular events following influenza vaccination. When stratified by baseline risk, we observed lower risk across all three outcomes in association with vaccination among higher-risk individuals. In this subgroup, relative risks were 0.72 (0.59-0.88) for AMI, 0.77 (0.59-0.99) for stroke, and 0.73 (0.45-1.19) for pulmonary embolism in the period 1-14 days following vaccination when compared to the background period. These associations remained essentially the same up to 180 days after vaccination. In contrast, the corresponding relative risks among subjects not using medications were 4.19 (2.69-6.52), 1.73 (0.91-3.31) and 2.35 (0.78-7.06). CONCLUSION: In this nationwide study, influenza vaccination was associated with overall cardiovascular benefit. This benefit was concentrated among those at higher cardiovascular risk as defined by medication use. In contrast, our results demonstrate no comparable inverse association with thrombosis-related cardiovascular events following vaccination among those free of cardiovascular medications at baseline. These results may inform the risk-benefit balance for universal influenza vaccination.

Potential causal factors of CFS/ME: a concise and systematic scoping review of factors researched.

BACKGROUND: Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is understood as a complex condition, likely triggered and sustained by an interplay of biological, psychological, and social factors. Little oversight exists of the field of causal research. This systematic scoping review explores potential causal factors of CFS/ME as researched by primary studies. METHODS: We searched eight databases for primary studies that examined potential causal factors of CFS/ME. Based on title/abstract review, two researchers independently sorted each study's factors into nine main categories and 71 subordinate categories, using a system developed with input given during a 2018 ME conference, specialists and representatives from a ME patient advocacy group, and using BMJ Best Practice's description of CFS/ME etiology. We also extracted data related to study design, size, diagnostic criteria and comparison groups. RESULTS: We included 1161 primary studies published between January 1979 and June 2019. Based on title/abstract analysis, no single causal factor dominated in these studies, and studies reported a mean of 2.73 factors. The four most common factors were: immunological (297 studies), psychological (243), infections (198), and neuroendocrinal (198). The most frequent study designs were case-control studies (894 studies) comparing CFS/ME patients with healthy participants. More than half of the studies (that reported study size in the title/abstract) included 100 or fewer participants. CONCLUSION: The field of causal hypotheses of CFS/ME is diverse, and we found that the studies examined all the main categories of possible factors that we had defined a priori. Most studies were not designed to adequately explore causality, rather to establish hypotheses. We need larger studies with stronger study designs to gain better knowledge of causal factors of CFS/ME.

Validation of Assisted Reproductive Technology in the Medical Birth Registry of Norway Versus the Norwegian Prescription Database.

BACKGROUND: Increasing attention has been given to the long-term effects of assisted reproductive technology (ART). This study assessed the validity and completeness of ART as registered in the Medical Birth Registry of Norway (MBRN) using drug prescription data from the Norwegian Prescription Database (NorPD) as reference. METHODS: In this nationwide registry validation study, we included all pregnancies recorded in the MBRN between 2005 and 2017. We estimated sensitivity, specificity, and positive and negative predictive value (PPV and NPV) of the MBRN, using data from the NorPD as reference. We obtained the total percentage of ART pregnancies that could be identified (completeness) from both registries using the capture-recapture method. We analyzed subgroups by maternal age, gestational length, mode of ART treatment, health region, and mode of registration of ART (ART institution or birth notification form). RESULTS: Twenty-three thousand seven hundred eighteen of a total 765,789 pregnancies were registered as ART pregnancies through the MBRN and 20,807 as ART pregnancies through the NorPD. The sensitivity of the MBRN was 85.1% (95% confidence interval [CI] = 84.7, 85.6) and the PPV was 74.7% (74.1-75.2). Sensitivity declined with increasing maternal age: 71.5% (69.4-73.7) in the age group 40-44 years, and 40.7% (22.2-59.3) in the ages above 45 years. Completeness when combining data was 96.2% (96.0-96.5). CONCLUSIONS: Our analysis shows that, when identifying women pregnant through ART, NorPD data complemented MBRN data to obtain a more complete count of all women giving birth after ART in Norway.

Risk conditions in children hospitalized with influenza in Norway, 2017-2019.

BACKGROUND: Norwegian children are more frequently hospitalized with influenza than adults. Little is known about the characteristics of these children. Our aim was to investigate the presence of pre-existing risk conditions and to determine the duration of influenza hospitalizations in children during two influenza seasons. METHODS: The Norwegian Patient Registry holds data on all hospitalized patients in Norway. We included all patients younger than 18 years hospitalized with a diagnosis of influenza during the influenza seasons 2017-18 and 2018-19. Pre-existing risk conditions for influenza were identified by ICD-10 diagnoses in the Norwegian Patient Registry. In addition, information on asthma diagnoses were also retrieved from the Norwegian Registry for Primary Health Care. To estimate the prevalence of risk conditions in the child population, we obtained diagnoses on all Norwegian children in a two-year period prior to each influenza season. We calculated age-specific rates for hospitalization and risk for being hospitalized with influenza in children with risk conditions. RESULTS: In total, 1013 children were hospitalized with influenza during the two influenza seasons. Children younger than 6 months had the highest rate of hospitalization, accounting for 13.5% of all admissions (137 children). Hospitalization rates decreased with increasing age. Among children hospitalized with influenza, 25% had one or more pre-existing risk conditions for severe influenza, compared to 5% in the general population under 18 years. Having one or more risk conditions significantly increased the risk of hospitalization, (Odds Ratio (OR) 6.1, 95% confidence interval (CI) 5.0-7.4 in the 2017-18 season, and OR 6.8, 95% CI 5.4-8.4 in the 2018-19 season). Immunocompromised children and children with epilepsy had the highest risk of hospitalization with influenza, followed by children with heart disease and lung disease. The average length of stay in hospital were 4.6 days, and this did not differ with age. CONCLUSION: Children with pre-existing risk conditions for influenza had a higher risk of hospitalization for influenza. However, most children (75%) admitted to hospital with influenza in Norway during 2017-2019 did not have pre-existing risk conditions. Influenza vaccination should be promoted in particular for children with risk conditions and pregnant women to protect new-borns.

Hospitalization following influenza infection and pandemic vaccination in multiple sclerosis patients: a nationwide population-based registry study from Norway.

Patients with multiple sclerosis (MS) are at increased risk of infections and related worsening of neurological function. Influenza infection has been associated with increased risk of various neurological complications. We conducted a population-based registry study to investigate the risk of acute hospitalization of MS patients in relation to influenza infection or pandemic vaccination in Norway. The entire Norwegian population in the years 2008-2014 was defined as our study population (N = 5,219,296). Information on MS diagnosis, influenza infection and vaccination were provided by Norwegian national registries. The self-controlled case series method was used to estimate incidence rate ratios (IRRs) with 95% confidence intervals (95% CI) in defined risk periods. 6755 MS patients were identified during the study period. Average age at first registration of an MS diagnosis was 51.8 years among men and 49.9 years among females (66.9%). The IRR for emergency hospitalization among MS patients the first week after an influenza diagnosis was 3.4 (95% CI 2.4-4.8). The IRR was 5.6 (95% CI 2.7-11.3) after pandemic influenza, and 4.8 (95% CI 3.1-7.4) after seasonal influenza. Pandemic vaccination did not influence risk of hospitalization [IRR within the first week: 0.7 (95% CI 0.5-1.0)]. Among MS patients, influenza infection was associated with increased risk for acute hospitalization while no increased risk was observed after pandemic vaccination. Influenza vaccination could prevent worsening of MS-related symptoms as well as risk of hospitalization.

Seasonal and pandemic influenza during pregnancy and risk of fetal death: A Norwegian registry-based cohort study.

Previous studies of fetal death with maternal influenza have been inconsistent. We explored the effect of maternal influenza-like illness (ILI) in pregnancy on the risk of fetal death, distinguishing between diagnoses during regular influenza seasons and the 2009/2010 pandemic and between trimesters of ILI. We used birth records from the Medical Birth Registry of Norway to identify fetal deaths after the first trimester in singleton pregnancies (2006-2013). The Norwegian Directorate of Health provided dates of clinical influenza diagnoses by primary-health-care providers, whereas dates of laboratory-confirmed influenza A (H1N1) diagnoses were provided by the Norwegian Surveillance System for Communicable Diseases. We obtained dates and types of influenza vaccinations from the Norwegian Immunisation Registry. Cox proportional-hazards regression models were fitted to estimate hazard ratios (HRs) of fetal death, with associated 95% confidence intervals (CIs), comparing women with and without an ILI diagnosis in pregnancy. There were 2510 fetal deaths among 417,406 eligible pregnancies. ILI during regular seasons was not associated with increased risk of fetal death: adjusted HR = 0.90 (95% CI 0.64-1.27). In contrast, ILI during the pandemic was associated with substantially increased risk of fetal death, with an adjusted HR of 1.75 (95% CI 1.21-2.54). The risk was highest following first-trimester ILI (adjusted HR = 2.28 [95% CI 1.45-3.59]). ILI during the pandemic-but not during regular seasons-was associated with increased risk of fetal death in the second and third trimester. The estimated effect was strongest with ILI in first trimester.

The Norwegian Patient Registry and the Norwegian Registry for Primary Health Care: Research potential of two nationwide health-care registries.

In Norway, the Directorate of Health is responsible for two nationwide registries - the Norwegian Patient Registry (NPR) and the Norwegian Registry for Primary Health Care (NRPHC) - which together cover all governmental-funded health care. The NPR (specialist health care) was established in 2008, while the NRPHC (primary health care) was established in 2017. Data from the NPR are extensively used in a large variety of studies. We expect that data from the NRPHC will increase in importance when the registry covers a longer time period. The NRPHC will be especially important for studying conditions mainly treated in primary care and for investigation of patient trajectories. The main aim of this paper is to give an overview of the history and content of the NPR and its research possibilities. In addition, we introduce the NRPHC as a possible future research tool and the potential for studying patient trajectories when combining data from the two registries.

SARS-CoV-2 in children and adolescents in Norway: confirmed infection, hospitalisations and underlying conditions. / Sars-CoV-2 hos barn og ungdom i Norge: påvist smitte, sykehusinnleggelser og underliggende tilstander.

BACKGROUND: Children and adolescents are at lower risk of disease caused by SARS-CoV-2. We describe the incidence of confirmed infection and hospitalisation of children and adolescents under the age of 20 in Norway, and specifically among those with underlying conditions. MATERIAL AND METHOD: The Norwegian Directorate of Health has collaborated with the Norwegian Institute of Public Health on the establishment of a data extraction system to monitor the coronavirus outbreak. Data from the specialist health service (Norwegian Patient Registry, NPR), and the primary health service (Norwegian Registry for Primary Health Care, NRPHC) are linked to data on positive SARS-CoV-2 tests from the Surveillance System for Communicable Diseases (MSIS). This covers all persons living in Norway as of 1 March 2020, with data on confirmed infection up to and including 13 May 2020 and on hospitalisations up to and including 30 April 2020. RESULTS: Of 8 125 persons with confirmed SARS-CoV-2 in the whole population, 493 (6.1 %) were under 20 years old. The median age of the under-20s was 15 years, and 252 (51 %) were girls. 3 % were hospitalised. No deaths were registered among patients aged under 20 in Norway. We found a somewhat larger share with confirmed SARS-CoV-2 in the group with diseases of the neuromuscular system. INTERPRETATION: Few children and adolescents have had SARS-CoV-2 confirmed, and only a very few have been hospitalised. Underlying conditions may result in a lower threshold for testing, and hence a higher incidence of confirmed infection in this group, although higher risk cannot be excluded.

Deaths after confirmed SARS-CoV-2 in Norway. / Dødsfall etter påvist SARS-CoV-2 i Norge.

BACKGROUND: Advanced age is the most important risk factor for death as a result of COVID-19, but there is a dearth of knowledge regarding the impact of chronic diseases. Using health registry data, we describe the disease profiles of persons who died after a confirmed infection with SARS-CoV-2 during the first three months of the pandemic in Norway. MATERIAL AND METHOD: Data from the specialist health service (Norwegian Patient Registry, NPR) and the primary health service (Norwegian Registry for Primary Health Care, NRPHC) were linked to information on positive tests for SARS-CoV-2 from the Norwegian Surveillance System for Communicable Diseases (MSIS) and on deaths from the National Population Register. The data retrieval included the Norwegian population as of 1 March 2020 with data for confirmed infections, hospitalisations and deaths until 31 May 2020. RESULTS: Of 8 412 persons with a confirmed SARS-CoV-2 infection, altogether 244 (2.9 %) died, whereof 133 (55 %) were men. Among those with a confirmed infection, the proportion who died varied from 0.2 % (age < 60 years) to 52 % (age ≥ 90 years). Altogether 92 (38 %) patients died in hospital. 25 (16 %) of those who died elsewhere had previously been hospitalised for COVID-19. The proportion with no registered chronic disease was 39 % in the age group < 70 years and 26 % in the age group ≥ 70 years. The disease distribution varied between those patients who had died in and outside of hospital, especially for diagnoses of diabetes, renal failure and dementia. INTERPRETATION: Among those who had a SARS-CoV-2 infection confirmed during the first three months of the pandemic in Norway, only a small proportion died. The majority of those who died were 70 years or older and had at least one chronic disease, but the disease profile varied between patients who died in and outside of hospital. Health registry data can help provide a better overview of and advice to risk groups in the population during an ongoing pandemic.

Underlying conditions in adults with COVID-19. / Underliggende tilstander hos voksne med covid-19.

BACKGROUND: Cardiovascular diseases, cancer, type-2 diabetes and chronic obstructive pulmonary disease (COPD) were initially noted as the most common diseases among individuals who were hospitalised for COVID-19. However, the evidence base is weak. The objective of this study is to describe how selected diseases were distributed among adults with confirmed COVID-19 (COVID-19 positive tests) and among those hospitalised for COVID-19 compared to the general population. MATERIAL AND METHOD: We used data from the Norwegian Patient Registry, the Norwegian Registry for Primary Health Care and the Norwegian Surveillance System for Communicable Diseases for adults from the age of 20 and older for the period 1 March 2020-13 May 2020. RESULTS: Of all those who tested positive for COVID-19, 7 632 (94 %) were aged 20 years or older, and 1 025 (13.4 %) of these had been hospitalised. Among those hospitalised with COVID-19, there was a higher proportion of individuals with cardiovascular diseases (18.3 % versus 15.6 %), cancer (6.9 % versus 5.4 %), type-2 diabetes (8.6 % versus 5.2 %) and COPD (3.8 % versus 2.7 %) than in the general population as a whole after adjusting for age. The proportion of hospitalised patients with asthma, other chronic respiratory disease, cardiovascular disease, ongoing cancer treatment, complications related to hypertension, obesity and overweight, neurological disorders and cardiac and renal failure was also higher than in the general population. There were few differences between persons who had tested positive for COVID-19 and the general population in terms of underlying conditions. INTERPRETATION: Among those hospitalised for COVID-19, there was a higher proportion of patients with underlying illnesses than in the general population. This may indicate that these patients tend to have a more severe course of disease or that they are more likely to be hospitalised compared to healthy individuals. The results must be interpreted with caution, since the sample of COVID-19 individuals is non-random.

Diagnosing autism spectrum disorder among children in Norway. / Diagnostisering av autismespekterforstyrrelser hos barn i Norge.

BACKGROUND: The percentage share of children who are diagnosed with autism spectrum disorder has increased considerably since the 1990s in Norway as well as in other countries. It has previously been demonstrated that there is considerable variation between counties with respect to diagnostic practice. MATERIAL AND METHOD: We calculated the percentage of children with autism spectrum disorder by using patient data obtained from the Norwegian Patient Registry and population data obtained from the National Registry. The calculations were made for the country as a whole as well as by county. The diagnostic assessments and documentation were mapped by linking the Norwegian Patient Registry with the Norwegian Mother, Father and Child Cohort study. We also reviewed patient records obtained from the specialist health service and considered whether diagnostic practice satisfied the research criteria for autism spectrum disorder. RESULTS: By the age of eight, 1.1 % of boys and 0.3 % of girls had been diagnosed with autism spectrum disorder. The overall percentages varied from 0.3 to 1.0 between counties. From 2008 to 2016, these percentages increased in all age groups. Our review of patient records included 503 children. In 95 % of cases the patient records provided a high standard of documentation that the diagnostic research criteria had been satisfied. The assessments were largely conducted in accordance with the guidelines drawn up by the various health trusts. INTERPRETATION: Autism diagnoses are generally well documented within the Norwegian specialist health service and meet the diagnostic criteria. In the counties that demonstrate a low prevalence of autism, it appears the health service fails to recognise autism in many children, particularly girls, or the diagnosis is determined late.

Tourette syndrome in children in Norway. / Tourettes syndrom hos barn i Norge.

BACKGROUND: Tourette syndrome first appears in childhood and is characterised by chronic motor and vocal tics. In other countries, the mean prevalence is estimated at 0.77 % in children aged 6-15 years. Diagnostic practice and treatment have not been investigated in Norway. MATERIAL AND METHOD: We used data retrieved from the Norwegian Patient Registry and the National Registry to calculate the percentage of children born during the period 2002-10 diagnosed with Tourette syndrome. The calculations were made for the country as a whole as well as by county. Drug therapy was investigated using data from the Norwegian Prescription Database. RESULTS: By the age of 12, altogether 0.43 % had received a diagnosis of Tourette syndrome, broken down into 0.71 % for boys and 0.15 % for girls. The overall percentage varied from 0.15 % to 1.23 % between the counties. For Norway as a whole, the percentage of diagnoses remained stable between 2008 and 2016. Psychiatric and neurological conditions were often present - the most common being hyperkinetic disorder (50 %) and autism spectrum disorder (11 %). Antipsychotic drugs, probably for the treatment of tics, were prescribed for 16 % in the year following the diagnosis. INTERPRETATION: The percentage of children with a diagnosis of Tourette syndrome is lower than the mean prevalence in population studies internationally. The diagnostic practice varies considerably from county to county.

Influenza and risk of later celiac disease: a cohort study of 2.6 million people.

OBJECTIVES: Influenza has been linked to autoimmune conditions, but its relationship to subsequent celiac disease (CD) is unknown. Our primary aim was to determine the risk of CD after influenza. A secondary analysis examined the risk of CD following pandemic influenza vaccination. METHODS: This nationwide register-based cohort study included 2,637,746 Norwegians (born between 1967-2013) followed during 2006-2014 with information on influenza diagnosed in primary or non-primary care, pandemic vaccination (Pandemrix), and subsequent CD. Cox regression yielded hazard ratios adjusted (HR) for socio-demographic characteristics and earlier healthcare use. RESULTS: During 13,011,323 person-years of follow-up 7321 individuals were diagnosed with CD (56/100,000 person-years). There were 351,666 individuals diagnosed with influenza, including 82,980 during the 2009-2010 pandemic, and 969,968 individuals were vaccinated. Compared with participants without influenza, who had a CD incidence of 55/100,000 person-years, those diagnosed with seasonal and pandemic influenza had a rate of 68 and 78, per 100,000 person-years, respectively. The HR for CD was 1.29 (95%CI, 1.21-1.38) after seasonal influenza and 1.29 (95%CI, 1.15-1.44) after pandemic influenza; HRs remained significantly increased one year after exposure, when restricted to laboratory-confirmed influenza, and after multivariate adjustments. The reverse association, i.e., risk of influenza after CD, was not significant (HR 1.05; 95%CI, 0.98-1.12). The HR for CD after pandemic vaccination was 1.08 (95%CI, 1.03-1.14). CONCLUSION: A positive association with influenza diagnosis is consistent with the hypothesis that infections may play a role in CD development. We could neither confirm a causal association with pandemic vaccination, nor refute entirely a small excess risk.

Diagnosis of hyperkinetic disorder among children in Norway. / Diagnostikk av hyperkinetisk forstyrrelse hos barn i Norge.

BACKGROUND: Hyperkinetic disorder is one of the most frequently used psychiatric diagnoses among children and adolescents in Norway. It has previously been shown that use of the diagnosis varies widely by county. MATERIAL AND METHOD: We estimated the proportion of children with hyperkinetic disorder using patient data from the Norwegian Patient Registry and population data from the Norwegian Population Registry. The estimations were made for both Norway as a whole and by county. Assessment and documentation of the diagnosis were surveyed by linking the Norwegian Patient Registry and the Norwegian Mother and Child Cohort Study. We reviewed medical records from specialist mental health services for children and adolescents and assessed whether the diagnoses met the research criteria for hyperkinetic disorder. RESULTS: At 12 years of age, 5.4 % of Norwegian boys and 2.1 % of Norwegian girls had been diagnosed with hyperkinetic disorder by specialist health services. The proportion of children varied between 1.4 % and 5.5 % among the counties. A review of medical records for 549 children showed that 49 % of the diagnoses were reliably documented in the records. The main reasons that the diagnosis was not documented were a discrepancy between the information in the medical record and diagnostic criteria (38 %) and inadequate differential diagnostic assessment (46 %). INTERPRETATION: There was considerable geographic variation in the proportions of children and adolescents with hyperkinetic disorder. A large percentage of the diagnoses were not reliably documented in medical records. The guideline for evaluation, diagnostics and medical recordkeeping should be reviewed.

Seizures, syndromes, and etiologies in childhood epilepsy: The International League Against Epilepsy 1981, 1989, and 2017 classifications used in a population-based cohort.

OBJECTIVE: The study provides updated information about the distribution of seizures, epilepsies, and etiologies of epilepsy in the general child population, and compares the old and new classification systems from the International League Against Epilepsy (ILAE). METHODS: The study platform was the Norwegian Mother and Child Cohort Study. Cases of epilepsy were identified through registry linkages and sequential parental questionnaires. Epilepsy diagnoses were validated using a standardized protocol, and seizures, epilepsies, and etiologies were classified according to the old (ILAE 1981/1989) and new (ILAE 2017) classifications. Information was collected through medical record reviews and/or parental telephone interviews. RESULTS: The study population included 112,744 children aged 3-13 years at the end of follow-up on December 31, 2012. Of these, there were 606 children with epilepsy (CWE). Distribution of seizure types varied by age of onset. Multiple seizure types were common with early onset. Focal epilepsies were the most common, occurring in 317 per 100,000 children in the study population and in 59% of CWE. Generalized epilepsies were found in 190 per 100,000 (35% of CWE). CWE with onset during the first 2 years of life had an even distribution of focal and generalized epilepsies, whereas focal epilepsies became dominant at later ages of onset. A definite cause of epilepsy had been demonstrated in 33% of CWE. The ILAE 1989 classification allowed for a broad syndrome category in 93% of CWE and a defined epileptic syndrome in 37%. With the ILAE 2017 classification, 41% of CWE had a defined epileptic syndrome and 63% had either a defined syndrome or structural-metabolic etiology. SIGNIFICANCE: The distribution of seizures and epilepsies is strongly dependent on age of onset. Despite diagnostic advances, the causes of epilepsy are still unknown in two-thirds of CWE. The ILAE 2017 classifications allow for a higher precision of diagnoses, but at the expense of leaving more epilepsies classifiable only at the mode of onset level.

Completeness and correctness of cerebral palsy diagnoses in two health registers: implications for estimating prevalence.

AIM: To assess completeness and correctness of cerebral palsy (CP) diagnoses in the Cerebral Palsy Register of Norway (CPRN) and the Norwegian Patient Register (NPR), and to estimate CP prevalence. METHOD: Among 747 883 Norwegian residents born from 1996 to 2007, 2231 had a diagnosis of CP in the NPR while 1441 were registered in the CPRN. Children registered in the CPRN were considered to have a valid CP diagnosis. For those with a diagnosis of CP only in the NPR, two paediatricians reviewed the hospital records. The prevalence rate of CP with 95% confidence intervals (CI) was calculated on the basis of the combined data sets. RESULTS: One thousand three hundred and ninety-eight children were registered with a diagnosis of CP in both registers, 43 children were only registered in the CPRN, and 824 only in the NPR. The review of hospital records revealed that 464 (59.5%) had CP. Thus, the NPR was 98% complete, and for 86% the diagnosis was correct. The completeness of the CPRN was 76%, while the diagnosis was considered correct for all children (100%). The resulting prevalence of CP was 2.5 (95% CI 2.4-2.7) per 1000. INTERPRETATION: To gain accurate estimates of prevalence rates of CP, it is essential to combine data sources and to validate register data.

The quality of severe mental disorder diagnoses in a national health registry as compared to research diagnoses based on structured interview.

BACKGROUND: Utilization of diagnostic information from national patient registries rests on the quality of the registered diagnoses. We aimed to investigate the agreement and consistency of diagnoses of psychotic and bipolar disorders in the Norwegian Patient Registry (NPR) compared to structured interview-based diagnoses given as part of a clinical research project. METHODS: Diagnostic data from NPR were obtained for the period 01.01.2008-31.12.2013 for all patients who had been included in the Thematically Organized Psychosis (TOP) study between 18.10.2002 and 01.09.2014 with a Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) diagnosis of schizophrenia (n = 537), delusional disorder (n = 48), schizoaffective disorder (n = 118) or bipolar disorder (n = 408). Diagnostic agreement between the primary DSM-IV diagnosis in TOP and the International Classification of Diseases, 10th revision (ICD-10) diagnoses in NPR was evaluated using Cohen's unweighted nominal kappa (κ). Diagnostic consistency was calculated as the proportion of all registered severe mental disorder diagnoses in NPR that were equivalent to the primary diagnosis given in the TOP study. RESULTS: The proportion of patients registered with the equivalent ICD-10 diagnosis as the primary DSM-IV diagnosis given in TOP was 84.2% for the schizophrenia group, 68.8% for the delusional disorder group, 76.3% for the schizoaffective disorder group, and 78.4% for the bipolar disorder group. Diagnostic agreement was good for schizophrenia (κ = 0.74) and bipolar disorder (κ = 0.72), fair for schizoaffective disorder (κ = 0.63), and poor for delusional disorder (κ = 0.39). Among patients with DSM-IV schizophrenia, 4.7% were diagnosed with ICD-10 bipolar disorder, and among patients with DSM-IV bipolar disorder, 2.5% were diagnosed with ICD-10 schizophrenia. Diagnostic consistency was 84.9% for schizophrenia, 59.1% for delusional disorder, 65.9% for schizoaffective disorder, and 91.0% for bipolar disorder. CONCLUSIONS: When compared to research-based diagnoses, clinical diagnoses of schizophrenia and bipolar disorder in the NPR are accurate and consistent, with minimal diagnostic overlap between the two disorders.

ADHD treatment and diagnosis in relation to children's birth month: Nationwide cohort study from Norway.

BACKGROUND: Studies from several countries have reported that children youngest in grade are at higher risk of attention-deficit/hyperactivity disorder (ADHD) diagnosis and treatment. Norwegian children start school the year they turn six, making children born in December youngest in their grade. We used data on medication, specialist healthcare diagnoses, and primary healthcare diagnoses from national registers to investigate associations between birth month and ADHD. METHODS: All children born in Norway between 1998 and 2006 ( N=509,827) were followed from age six until 31 December 2014. We estimated hazard ratios for ADHD medication and diagnoses by birth month in Cox proportional-hazards models. We compared risk among siblings to control for potentially confounding socioeconomic factors, and assessed risk of receiving ADHD medication by birth month while attending different grades in cross-sectional time-series analyses. RESULTS: At end of follow-up, 5.3% of boys born in October-December had received ADHD medication, compared with 3.7% of boys born in January-March. Corresponding numbers for girls were 2.2% and 1.3%, respectively. The adjusted hazard ratio for ADHD medication for children born in October-December (reference: January-March) was 1.4 (95% confidence interval: 1.4-1.5) for boys and 1.8 (1.7-2.0) for girls. Analyses with diagnoses as outcome showed consistent results, and analyses restricted to siblings within the study population also supported the findings. Analysis by grade revealed an increased risk for children born late in the year from grade 3 onwards, with most marked differences in higher grades. CONCLUSIONS: Children youngest in grade had the highest risk of receiving ADHD treatment. Differences were most marked among older children.