Familial hemiplegic migraine (FHM) is a rare autosomal dominantly inherited subtype of migraine with aura. The clinical characteristics of FHM have been described previously in selected materials or case studies, but population-based studies are important in order to analyse the full spectrum of the disorder. The aim of the present study was to perform a systematic search for familial cases of migraine with an aura that included motor weakness in order to generate non-selected material of as many FHM cases as possible in the Danish population of 5.2 million inhabitants, and to compare this material with already available population-based clinical descriptions of migraine with typical aura (MA). Due to the rarity of FHM, traditional population-based methods were not feasible. Therefore, the search strategy employed a computer search of the National Patient Register, screening >27 000 case records from headache clinics and private neurologists, and advertisements. A total of 147 affected FHM patients from 44 families were identified. FHM patients most often had all four 'typical' aura symptoms (visual, sensory, aphasic and motor symptoms) and all had at least two of these aura symptoms during FHM attacks. The motor, sensory and visual aura symptoms were all similar in type to the motor, sensory and visual aura symptoms in MA, but FHM had a statistically significantly longer duration of the visual and sensory aura symptoms, and these and other aura symptoms often fulfilled the criteria of the International Headache Society for prolonged aura. In addition, 69% had basilar migraine (BM) symptoms during FHM attacks. The order of the aura symptoms was usually visual, followed by sensory, aphasic, motor and, lastly, basilar-type migraine symptoms. Headache was present in 99% of FHM patients during FHM attacks, whereas the aura symptoms more often occurred without headache in MA. Headache duration was significantly longer in FHM compared with MA. Based on these data, we suggest more precise diagnostic criteria for FHM and a more clear clinical distinction between FHM and BM. Our results have significant implications for case finding in genetic studies and for clinical migraine differential diagnosis.

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How did the register come about?The Copenhagen School Health Records Register (CSHRR) is a database of health examination information on more than 350 000 schoolchildren who ever attended school in the central municipality of the capital city of Denmark. For longer than 100 years, school-based health care has been provided to children in Copenhagen, 1 and from the 1930s, the material was systematically recorded on individual health cards. The CSHRR results from the retrieval and computerization of data from every health card. Information from the register can be used on its own and it can also be linked to a variety of health registers and other cohort studies in Denmark.In the early 1980s, an effort was made to locate the cards when researchers wanted to examine childhood exposures in a cohort of severely obese Danish draftees. [2][3][4][5] Locating these records was a large undertaking, as previously the cards had been found only for a small number of subjects. [6][7][8] Retrieving the cards was a challenge because they were stored in boxes under the attic eaves of an old tall school building. The necessary cards were retrieved and computerized for the draftee study, but recognizing their tremendous research potential, efforts were made to ensure they were properly archived. Fortunately, this realization occurred just in time-the cards were slated for destruction. The Cancer Registry, run by the Danish Cancer Society, rescued the records and they are now preserved in the Copenhagen Municipal Archives. In the 25 years following the initial study on the draftees, a systematic computerization of information on schoolchildren in Copenhagen born from 1930 to 1983 was undertaken in phases depending on available resources. The process is ongoing, and records from recent school years are added as they become available.

The objectives of the present study were to describe the clinical characteristics of patients with severe familial non-hemiplegic migraine with aura (NHMA) and to compare these data to those from cases in previous population-based Danish studies using the same methodology. NHMA families were recruited from the Danish patient registry and from Danish neurology practices. A total of 362 NHMA patients were diagnosed according to the 1988 International Headache Society criteria using a validated semistructured physician-conducted interview. Visual aura occurred in almost every NHMA attack. In aura without headache visual aura occurred primarily in isolation. Aura without headache was most common in older, male patients. Several clinical characteristics of familial NHMA differed from migraine with aura in the general population: firstly, the age at onset was lower, secondly, the age at cessation was higher, thirdly, aura symptoms were more severe and finally, the co-occurrence of migraine without aura was higher in familial NHMA. There seems to be a correlation between more severe symptoms and familial aggregation. These results have both clinical and scientific implications.

The objective of the present study was to use systematic nation-wide case-finding methods to establish the prevalence and sex ratio of hemiplegic migraine (HM) in the entire Danish population of 5.2 million inhabitants. Affected patients were identified from three different recruitment sources: the National Patient Register, case records from private practising neurologists and advertisements. Based on the observed number of affected patients from each case-finding method, it was attempted to estimate the total number of affected patients by means of the statistical method known as capture-recapture. Two hundred and ninety-one affected patients were identified; 147 were familial HM from 44 different families, 105 were sporadic HM and 39 were unclassifiable HM. The HM sex ratio (M:F) was 1:3. Based on the identified number of affected patients the prevalence of HM at the end of 1999 was estimated to be 0.01% in Denmark, where the familial and sporadic form were equally frequent.

Background: Uncertainties exist about the strength of the relation between socio-economic position and depressive disorders. The aim of this study was to investigate the association between education, occupation, employment and income and depressive disorders measured as minor and major depression as well as antidepressant prescriptions.Methods: Data were collected from a Danish cross sectional study collected year 2000, comprising 9254 subjects, 55% women, and aged 36-56 years. We used register-based information on education, income and prescription.Results: The prevalence of major depression DSM-IV algorithm was 3,3% among men and women, whereas minor depression and prescriptions revealed statistically significant higher prevalence among females. A social gradient was found for all depressive end-points with the strongest estimates related to major depressive disorder (MDD). The associations were as follows: MDD and low education odds ratio (OR) 2.38 (CI 95% 1.68 to 3.37), MDD and non-employment OR 11.67 (CI 95% 8.06 to16.89), MDD and low income OR 9.78 (CI 95% 6.49 to 14.74). Education only explained a minor part of the association between nonemployment and depressive disorders and no associations were found between education and prescription. This indicates a strong two-way association between depression and nonemployment, low-income, respectively. Conclusion:We found a social gradient in depressive disorders regardless of socio-economic position being measured by education, occupation, employment or income. Severe socioeconomic consequences of depression are indicated by the fact, that the associations with non-employment and low income were much stronger than the association with low education.

It is a widely held belief in public health and clinical decision-making that interventions or preventive strategies should be aimed at patients or population subgroups where most cases could potentially be prevented. To identify such subgroups, deviation from additivity of absolute effects is the relevant measure of interest. Multiplicative survival models, such as the Cox proportional hazards model, are often used to estimate the association between exposure and risk of disease in prospective studies. In Cox models, deviations from additivity have usually been assessed by surrogate measures of additive interaction derived from multiplicative models-an approach that is both counter-intuitive and sometimes invalid. This paper presents a straightforward and intuitive way of assessing deviation from additivity of effects in survival analysis by use of the additive hazards model. The model directly estimates the absolute size of the deviation from additivity and provides confidence intervals. In addition, the model can accommodate both continuous and categorical exposures and models both exposures and potential confounders on the same underlying scale. To illustrate the approach, we present an empirical example of interaction between education and smoking on risk of lung cancer. We argue that deviations from additivity of effects are important for public health interventions and clinical decision-making, and such estimations should be encouraged in prospective studies on health. A detailed implementation guide of the additive hazards model is provided in the appendix.