Evaluating the use and limitations of the Danish National Patient Register in register-based research using an example of multiple sclerosis.

BACKGROUND: The Danish National Patient Register, Landspatientregistret (LPR), is a register of all hospital discharges and outpatient treatments in Denmark. AIMS: It is increasingly used in research so it is important to understand to what extent this can be used as an accurate source of information. Virtually all patients in Denmark with multiple sclerosis (MS) are reported to the Combined MS Registry (DMSR), so this was used as the standard which the LPR was compared against. METHODS: All residents of Denmark are assigned a unique Civil Register (CPR) number; this was used to compare data between registers. The LPR completeness was estimated by the proportion of cases from the DMSR that could be retrieved from the LPR. The LPR validity was estimated by the proportion of cases, listed in the LPR and DMSR, in whom the MS diagnosis could be confirmed as definite/probable/possible by the DMSR. RESULTS: We found that 86.9% of those who were DMSR listed with an approved MS diagnosis were also listed in the LPR with a MS diagnosis. The diagnosis was valid in 96.3% of patients listed in the LPR when compared against the DMSR. CONCLUSIONS: The low completeness reduces the usefulness of the LPR in epidemiological MS research, in particular incidence studies. The study also found that the completeness of the LPR could be increased to 92.8% by including LPR records from other departments in addition, but this reduced the validity of the LPR to 95.1%. However, these results cannot uncritically be applied to registration of other diseases in the LPR.

Antidepressant treatment among social workers, human service professionals, and non-human service professionals: A multi-cohort study in Finland, Sweden and Denmark.

BACKGROUND: Social workers have an elevated risk for mental disorders, but little is known about their antidepressant treatment. AIMS: To examine any and long-term antidepressant treatment among social workers in Finland, Sweden and Denmark. METHODS: We linked records from drug prescription registers to three prospective cohorts: the Finnish Public Sector study, years 2006-2011, and nation-wide cohorts in Sweden and Denmark, years 2006-2014, including a total of 1.5 million employees in (1) social work, (2) other social and health care professions, (3) education and (4) office work. We used Cox proportional hazards models to estimate hazard ratios for any and long-term (>6 months) antidepressant treatment among social workers compared to the three reference occupational groups and carried out meta-analyses. RESULTS: During follow-up, 25% of social workers had any prescriptions for antidepressants (19-24% reference occupations) and 20% for long-term treatment (14-19% reference occupations). The pooled effects for any and long-term treatment showed that probabilities were 10% higher in social workers compared to other health and social care professionals and 30% higher compared to education and non-human service professionals. Probabilities for any treatment in the three countries were relatively similar, but for long-term treatment social workers in Finland had a greater risk compared with other human service professions. LIMITATIONS: There were differences between the cohorts in the availability of data. Specific diagnoses for the antidepressant treatment were not known neither adherence to treatment. CONCLUSION: Social workers have a higher risk for any and long-term antidepressant treatment than other human and non-human service professionals.

Long-term survival and causes of death after stroke.

BACKGROUND AND PURPOSE: As part of the Danish contribution to the World Health Organization (WHO) MONICA (Monitoring Trends and Determinants in Cardiovascular Disease) Project, a register of patients with stroke was established in 1982. The purpose of the present study was to analyze long-term survival and causes of death after a first stroke and to compare them with those of the background population. METHODS: The study population comprised all subjects aged 25 years or older who were resident in a geographically defined region in Copenhagen County. All stroke events in the study population during 1982-1991 were ascertained and validated according to standardized criteria outlined for the WHO MONICA Project. After completion of the stroke registry at the end of 1991, all patients were followed up by record linkage to official registries. Standardized mortality ratios were calculated for various causes of death and periods after the stroke. RESULTS: The estimated cumulative risks for death at 28 days, 1 year, and 5 years after onset were 28%, 41%, and 60%, respectively. Compared with the general population, nonfatal stroke was associated with an almost 5-fold increase in risk for death between 4 weeks and 1 year after a first stroke and a 2-fold increase in the risk for death subsequent to 1 year. The excess mortality rate in stroke patients was due mainly to cardiovascular diseases but also to cancer, other diseases, accidents, and suicide. The probability for long-term survival improved significantly during the observation period for patients with ischemic or ill-defined stroke. CONCLUSIONS: Stroke is a medical emergency associated with a very high risk for death in the acute and subacute phases and with a continuous excess risk of death. Better prevention and management of strokes may improve the long-term survival rate.

Survival of patients with multiple sclerosis in Denmark: a nationwide, long-term epidemiologic survey.

We estimated survival probability and excess death rates for patients with MS on the basis of data from the Danish Multiple Sclerosis Registry, which includes virtually all patients diagnosed with MS in Denmark (population, five million) since 1948. We reviewed and reclassified all case records according to standardized diagnostic criteria. By linkage to the Danish Central Population Registry, we lost to follow-up only 25 patients who had emigrated. The median survival time from onset of the disease was 28 years in men (compared with 40 years in the matched general male population) and 33 years in women (versus 46 years). The median survival time from diagnosis was 22 years in men (versus 37 years) and 28 years in women (versus 42 years). The excess death rate between onset and follow-up (observed deaths per 1,000 person-years minus the expected number of deaths in a matched general population) was 14.3 in men, which was significantly higher than in women (12.0). Excess mortality increased with age at onset of MS in people of each sex. The 10-year excess death rate has decreased significantly in recent decades. Excess mortality was highest in cases with cerebellar symptoms at onset.

Optic neuritis as onset manifestation of multiple sclerosis: a nationwide, long-term survey.

OBJECTIVE: To determine the predictive value on survival of optic neuritis (ON) as onset manifestation of MS. METHODS: We used data obtained from the Danish Multiple Sclerosis Registry, which includes virtually all patients diagnosed with MS in Denmark. From 1949 to 1990, 7,548 unselected patients fulfilling standardized diagnostic criteria of MS were registered. RESULTS: The onset manifestation of MS was known in 6,923 patients, and was ON in 1,282 patients (19%). The mean age at onset was 31.1 years for these patients compared with 34.8 years for patients with another or unknown onset manifestation of MS (non-ON) (p < 0.001). The mean delay from the first known manifestation of MS to the final diagnosis of MS was 6.1 years (ON) and 4.2 years (non-ON). The median survival time from onset of ON was 30 years in men (compared with 41 years in the matched general male population) and 40 years in women (versus 47 years). The excess death rate increased with age at onset of MS in people of each sex. Excess death rate for women differed significantly between patients with ON as onset manifestation and patients with another or unknown onset manifestation of MS (8.3 versus 13.0). In patients with ON as onset manifestation of MS, the excess death rate was significantly higher in men (14.0) than in women (8.3). CONCLUSION: ON as onset manifestation of MS indicates a more favorable prognosis of survival of MS judged by excess death rate only in women.

Survival and cause of death after myocardial infarction: the Danish MONICA study.

As part of the Danish WHO MONICA study, a register of patients with myocardial infarction was established in 1982, covering 11 municipalities in the western part of Copenhagen County, Denmark. During the period 1982-91, all cases of myocardial infarction among citizens aged 25-74 years were registered and validated according to the criteria set up for the WHO MONICA project. Short-term (28 days) and long-term (up to 15 years) survival in three periods were compared. The rate of mortality after a non-fatal myocardial infarction was compared with that of the general population, and causes of death were analyzed. Short-term survival did not change during the study period, whereas long-term survival improved for men but did not change for women. The excess mortality rate among female patients over that of the general population was due to ischemic heart disease, other cardiovascular diseases, cancer and other diseases. The excess mortality among male patients was due only to cardiovascular diseases.

Trends in selected biological risk factors for cardiovascular diseases in the Danish MONICA population, 1982-1992.

Data from 6695 men and women of ages 30, 40, 50, and 60 years, examined in the Danish WHO MONICA surveys in 1982-84, in 1986-87, and in 1991-92, were analyzed to estimate secular trends in body height and weight, blood pressure, and serum total, HDL-, and LDL-cholesterol, and triglyceride. Body height increased 0.1% per year, and body mass index increased 0.4% per year in women. Diastolic blood pressure increased 0.4% per year in women and 0.6% per year in 60-year-old men. HDL cholesterol declined 0.4% per year. Body mass indices in men, diastolic blood pressures in men <60 years of age, systolic blood pressures, total- and LDL cholesterol and triglyceride did not change. The levels of biological risk factors in the Danish WHO MONICA study population did not show trends during the 1980s that help explain the declining incidence of myocardial infarction in the population.

Incidence of myocardial infarction in the Danish MONICA population 1982-1991.

BACKGROUND: Cardiovascular mortality has been declining in Denmark over the past 20 years. Trends in incidence of myocardial infarction (MI) over the period 1982-1991 are described within the framework of the World Health Organization MONICA Project. METHODS: The DAN-MONICA heart register included all cases of MI in 25-74-year-old men and women living in 11 municipalities around Glostrup County Hospital evolving over a period of 10 years. They were identified retrospectively based mainly on relevant ICD diagnoses in death certificates and hospital discharge reports. Cases meeting WHO-MONICA criteria for definite or possible MI, recurrent as well as first-ever MI, were registered. Subsequent tracing of cases through national registers on deaths and hospitalizations by means of the patient's civil registration number ensured the completeness of the registration. RESULTS: A total of 6025 cases of MI occurred in the period, 4532 among men and 1493 among women. A total of 2923 men and 1047 women had a first-ever MI in the period. The age-standardized rates show a definite decline over the registration period for men and a less distinct decline for women. CONCLUSIONS: The DAN-MONICA heart register meets the requirements for completeness and uniformity throughout the registration period. Causes and magnitude of bias are well described. Even when possible sources of bias are taken into account, the incidence of MI decreased significantly over the 10-year-period 1982-1991 by an average of 5.0% per year for men and 3.5% per year for women.

How good is the Prevent model for estimating the health benefits of prevention?

STUDY OBJECTIVE: Prevent is a public health model for estimating the effect on mortality of changes in exposure to risk factors. When the model is tested by simulating a development that has already taken place, the results may differ considerably from the actual situation. The purpose of this study is to test the Prevent model by applying it to a synthetic cohort in which the development is unaffected by concealed factors. DESIGN: A micro-simulation model was developed to create basic data for Prevent and give "exact" results as to changes in risk factor prevalences and mortality. The estimates of Prevent simulations were compared with the "exact" results. MAIN RESULTS: Modelling one risk factor related to a cause specific mortality gave fairly similar results by the two methods. Including two risk factors Prevent tends slightly to overestimate the health benefits of prevention. CONCLUSIONS: The differences between the "exact" mortality and the Prevent estimates will be small for realistic scenarios and Prevent provide reasonable estimates of the health benefits of prevention.

Socioeconomic status and trends in risk factors for cardiovascular diseases in the Danish MONICA population, 1982-1992.

STUDY OBJECTIVE: The decline in cardiovascular mortality in Denmark during the 1980s has been greatest in the highest socioeconomic groups of the population. This study examines whether the increased social inequality in cardiovascular mortality has been accompanied by a different trend in cardiovascular risk factors in different educational groups. DESIGN: Data from three cross sectional WHO MONICA surveys conducted in 1982-84, 1987, and 1991-92, were analysed to estimate trends in biological (weight, height, body mass index, blood pressure, and serum lipids) and behavioural (smoking, physical activity during leisure, and eating habits) risk factors in relation to educational status. SETTING: County of Copenhagen, Denmark. PARTICIPANTS: 6695 Danish men and women of ages 30, 40, 50, and 60 years. MAIN RESULTS: The prevalence of smoking and heavy smoking decreased during the study but only in the most educated groups. In fact, the prevalence of heavy smoking increased in the least educated women. There was no significant interaction for the remaining biological and behavioural risk factors between time of examination and educational level, indicating that the trend was the same in the different educational groups. However, a summary index based on seven cardiovascular risk factors improved, and this development was only seen in the most educated men and women. CONCLUSION: The difference between educational groups in prevalence of smoking increased during the 1980s, and this accounted for widening of an existing social difference in the total cardiovascular risk.

[Predicted effect of smoking cessation of tobacco-related mortality]. / Forventet effekt på tobaksrelateret dødelighed af nedsat cigaretforbrug.

INTRODUCTION: Cigarette smoking is a serious threat against public health and the most important preventable cause of death. The purpose of this study is to predict the effect on smoking-attributable mortality in Denmark by reducing the number of cigarette smokers. MATERIALS AND METHODS: The simulation model "Prevent" is used. This model operates with the population size and death rates in 1993, data on cigarette smoking from 1973 to 1992 and relative risks for the association between cigarette smoking and lung cancer, chronic bronchitis and emphysema, ischaemic heart disease and stroke. The influence of reduced cigarette smoking on mortality due to these diseases is studied. The expected effect on a smoke-free year group is estimated and so is the effect of the implementation of targets in the Danish Government's Public Health Programme 1999-2008. RESULTS: For the smoke-free year group death rates of ischaemic heart disease are reduced by one third for men and one half for women compared to unchanged cigarette smoking. Death rates of lung cancer, chronic bronchitis and emphysema would be approx. five times lower. If the proportion of Danish cigarette smokers could be reduced by one third over a period of ten years the reduced mortality due to lung cancer, chronic bronchitis and emphysema, ischaemic heart disease and stroke would increase the population (five mio. individuals) by 25,000 after 20 years. DISCUSSION: Intervention against cigarette smoking, especially among young people, would massively reduce mortality from several diseases in the long term. Also in the short term mortality would be reduced substantially by reducing the number of cigarette smokers.

[Prediction of ischemic heart disease mortality in Denmark 1982-1991 using the simulation model Prevent]. / Forudsigelse af udviklingen i dødelighed af iskaemisk hjertesygdom i Danmark 1982-1991 ved anvendelse af simulationsmodellen Prevent.

The simulation model "Prevent" estimates the effect on mortality of changes of exposures to risk factors taking the multifactorial nature of the associations between risk factors and diseases, time dimensions, and demography into account. The objective of the study is to compare the actual development of ischaemic heart disease mortality in Danmark from 1982 to 1991 with the estimated mortality based on the development of four risk factors. The sources of data used in the study are national population data and mortality rates and prevalences of risk factors from population surveys (Glostrup Population Studies). Relative risk estimates are those implemented in the Dutch version of Prevent based on international literature. The risk factors are: tobacco smoking, hypertension, cholesterol, and alcohol consumption. Results are given for ages below 65 years. The pronounced decline in mortality of ischaemic heart disease in Denmark cannot be foreseen by the model based on the development of the associated risk factors. However, the combined trend of risk factors for the last 10 to 15 years is only modest and does not indicate the dramatic decline in mortality. Prevent is too simple to make a satisfactory forecast of mortality, which however, is not the main purpose of the model. By comparing the development of a reference and an intervention population the effects of unknown factors are to some extent eliminated and the model may therefore give a good impression of the benefits of preventive interventions.

[Occurrence of colds and coughs among adult Danes. Epidemiological data from the DIKE (Danish Institute for Clinical Epidemiology) population study]. / Forekomsten af forkøleslse, snue og hoste blandt voksne danskere. Epidemiologi belyst ved DIKE's befolkningsundersøgelser.

The occurrence of upper respiratory symptoms among adult Danes was examined by the use of data from the Danish Health and Morbidity Survey 1986-1987. In this study, 14.0 per cent of 6,672 individuals reported complaints of colds or coughs (CC) during the two-week period preceding the interview. Reporting of CC decreased with age, but there was no sex difference. A multivariate analysis, including a number of suspected exposure variables, showed that CC was reported significantly more frequently (OR 1.42) by individuals also reporting exposure to external health risks in their homes. The reporting of CC was not associated with occupational exposure, psychological stress, spare time physical activity or smoking habits. Using bivariate analysis, it was shown that exposure to external health risks in the home was reported more frequently among women than men. The results indicate, that exposure to external health risks in dwellings contributes significantly to the total morbidity among adult Danes. However, improvement of the validity of information about exposure by means of more objective methods is required.

[The dietary awareness of Danish adults]. / Voksne danskeres kostbevidsthed.

By means of an interview investigation of a representative sample comprizing 4,753 adult Danes over the age of 15 years, the attempted dietary principles of the population are illustrated. 60% of the population try to avoid certain foodstuffs from the point of view of health and 75% include certain foodstuffs in their diets for the same reason. The persons who particularly follow the dietary recommendations made in recent years, which consist of avoiding fat and including coarse bread, vegetables and fruit in the diet are women, aged 25-44 years, individuals with high net incomes and persons living in the suburbs of the capital and in the three largest Danish provincial towns. The efforts to achieve healthy dietary habits are, in addition, associated with non-smoking and moderate alcohol consumption. During the past five years, the proportion of Danes who try to alter dietary habits has increased by approximately 10%. During the same period, the actual average diet has, however, not altered in the same positive direction. The dietary principles aimed at and which are reported here are, therefore, expression of Danes' awareness of dietary principles rather than the actual behaviour. Thus, despite optimal knowledge, barriers exist which prevent alteration of dietary behaviour.

[Survival in disseminated sclerosis in Denmark. A nation-wide study of the period 1948-1986]. / Overlevelsen ved dissemineret sklerose i Danmark. En landsdoekkende undersøgelse for perioden 1948-1986.

We estimated survival probability and excess death rates for patients with multiple sclerosis (MS) on the basis of data from the Danish Multiple Sclerosis Registry, which includes virtually all patients diagnosed with MS in Denmark since 1948. We reviewed and reclassified all case records according to standardized diagnostic criteria. By linkage to the Danish Central Population Registry and the National Registry of Causes of Death complete follow-up of all MS patients was achieved, with the exception of 25 patients who had emigrated. A total of 2300 of the 6727 MS patients included in the study had died before the onset of the disease was 28 years in men (compared with 40 years in the matched general male population) and 33 years in women (versus 46 years). The excess death rate between onset and follow-up (observed deaths per 1000 person-year minus the expected number of deaths in a matched general population) was 14.3 in men, which was significantly higher than in women (12.0). Excess mortality increased with age at onset of MS in people of each sex. The 10-year excess death rate has decreased significantly in recent decades. Excess mortality was highest in cases with cerebellar symptoms at onset.

[Occupational blood exposure among Danish physicians--incidence and risk factors]. / Erhvervsbetinget blodeksposition blandt danske laeger--incidens og risikofaktorer.

In a nation-wide questionnaire survey, the incidence and risk factors of percutaneous (PCE) and mucocutaneous (MCE) blood exposure among doctors in Denmark were studied. Of 9375 doctors, 6256 (67%) responded and 6005 were included for analysis. The highest incidence per person-risk-year (pry) was found in General Surgery, Neurosurgery, Obstetrics-Gynaecology and Orthopaedic Surgery (6.2-8.5 PCE/pry and 7.3-8.8 MCE/pry) followed by Anaesthesiology and Oto-rhinolaryngology (2.6-3.1 PCE/pry and 6.0-6.9 MCE/pry) and Pathology, Internal medicine, Radiology and Paediatrics (0.8-1.3 PCE/pry and 1.3-2.9 MCE/pry). Employment as senior as compared to junior doctor was associated with a higher risk of PCE and MCE among surgeons and a higher risk of PCE in anaesthetists, but a lower risk of PCE and MCE in Internal Medicine, Radiology and Paediatrics. Only 35% adhered to the basic principles of universal precautions and non-compliance was associated with a considerably increased risk of exposures, especially in non-surgical specialties. In conclusion, we found an unacceptably high incidence of occupational blood exposures among Danish doctors and preventive measures to reduce the incidence are strongly needed.

[Survival and cause of death after traumatic spinal cord injury. A long-term epidemiological study]. / Overlevelse og dødsårsager efter traumatisk rygmarvsskade. Et epidemiologisk langtidsstudie.

Life expectancy among individuals with spinal cord injuries (SCI) has remained lower than normal, even with optimal medical management. But improvement has been achieved, as shown by this study of an unselected population of survivors of traumatic SCI, dead or still living. There has been complete follow-up over four decades. The survey included a total of 888 individuals who had survived the injury and were rehabilitated at the Centre for the Spinal Cord Injured, East-Denmark between 1.1.1953-31.12.1990. At the end of the follow-up, 31st of December 1992, 236 had died. The most common causes of death were lung diseases, ischaemic heart diseases and suicide. The Standardised Mortality Ratios (SMRs) were highest for septicaemia, uraemia and pneumonia. Likewise, except for pneumonia, suicide and ischaemic heart disease, a decrease over time in SMRs was seen for all causes of death. The patterns of causes of death in the study group begin to approximate those of the general population.

[Mortality during the first six years after cholecystectomy. A review of all cholecystectomies in women in Denmark during 1977-1981]. / Dødeligheden i de første seks år efter kolecystektomi. Opgørelse af samtlige kolecystektomier blandt kvinder i Danmark i perioden 1977-1981.

It has been a prevailing assumption that cholecystectomy patients by and large follow a pattern of survival similar to that of the normal population. This paper presents a population-based study of the long-term survival after cholecystectomy in order to reassess this assumption. Based on data available in the Danish National Hospital Register, the records of all Danish women who were operated between 1977 and 1981 were examined and studied up to six years subsequent to surgery. Cholecystectomy patients who were free of diagnosed cancer and who had no major co-surgery (n = 11,123) were compared to both hysterectomy patients and a sample of the female population. Adjusting for age and other covariates, patients with psychiatric hospital admissions prior to surgery experienced a threefold risk of dying within six years after surgery. Patients with prior somatic admissions and patient with acute admissions had a relative risk (RR) of about 1.5. Cholecystectomy patients had a significantly increased mortality when compared to hysterectomy patients, RR = 1.3 (1.1-1.6), and to the population sample. Heart diseases and cancer occurred significantly more often as causes of death among cholecystectomy patients when compared to hysterectomy patients, but our data suggest that the occurrence of many other causes of death may be increased among cholecystectomy patients as well. The authors concluded that cholecystectomy patients are subject to relatively higher levels of mortality than previously assumed in parts of the literature. Furthermore, the increase seems to be attributable to a multitude of causes of death. The most likely explanation of the excess mortality among cholecystectomy patients is that gallbladder patients are relatively fragile. Indeed, with this vulnerable group of patients the potential trauma of the surgical intervention itself needs careful consideration.

[Postoperative mortality after cholecystectomy. A survey of all cholecystectomies among women in 1977-1981]. / Postoperativ mortalitet ved kolecystektomi. Opgørelse vedrørende samtlige kolecystektomier blandt kvinder i Danmark i perioden 1977-1981.

This paper assesses the risk of dying within thirty days of admission among 13,854 women who had a cholecystectomy performed as the principal operation during the period 1977-81. The overall crude mortality rate was 1.2%. Women who had a simple elective cholecystectomy performed had a mortality rate (0.2%) similar to women who had a simple hysterectomy, but significantly higher than in the general female population. High age, acute admission, admission to hospital in the three months prior to the index admission, the number of discharge diagnoses, and the geographical region were significantly associated with increased mortality. The higher mortality associated with exploration of the common bile duct disappeared when number of discharge diagnoses was taken into account. As regards early mortality, it is concluded that simple elective cholecystectomy is a safe procedure before the age of 50-60 years. Exploration of the common bile duct may not be as important an independent factor as previous assumed.

[Trends in selected biological risk factors of cardiovascular diseases in the Danish MONICA population 1982-1992]. / Udviklingen i udvalgte biologiske risikofaktorer for kardiovaskulaere sygdomme i den danske MONICA-population 1982-1992.

INTRODUCTION: The incidence rate of a first myocardial infarction declined 3-5% annually in the Danish WHO MONICA population in the period from 1982 to 1991. The aim of this study was to investigate whether levels of the most commonly considered biological traits associated with cardiovascular risk have changed in the Danish MONICA population during this period. METHOD: Data from 6,695 men and women of 30, 40, 50 and 60 years of age, examined in the Danish WHO MONICA surveys in 1982-1984, 1986-1987, and 1991-1992, were analysed to estimate temporal trends in body height and weight, blood pressure, and serum total, HDL, and LDL cholesterol, and triglyceride. RESULTS: Body height increased by 0.1% per year and the body mass index by 0.4% per year in women. The diastolic blood pressure increased 0.4% per year in women and 0.6% per year in 60-year-old men. HDL cholesterol declined 0.4% per year. Body mass indices in men, diastolic blood pressures in men < 60 years of age, systolic blood pressures, total and LDL cholesterol and triglyceride did not change. DISCUSSION: The levels of biological risk factors in the Danish WHO MONICA study population did not show trends during the 1980s that contribute to explain the declining incidence of myocardial infarction in the population.