Pedersen CB, Gotzsche H, Moller JO, Mortensen PBThe Danish Civil Registration system. A cohort of eight million persons. Dan Med Bull 53: 441-449

Article · December 2006with45 Reads
Source: PubMed
Abstract
The Danish Civil Registration System (CRS) was established in 1968, where all persons alive and living in Denmark were registered. Among many other variables, it includes individual information on personal identification number, gender, date of birth, place of birth, place of residence, citizenship, continuously updated information on vital status, and the identity of parents and spouses. To evaluate the quality and completeness of the information recorded on persons in the CRS, we considered all persons registered on November 4, 2005, i.e. all persons who were alive and resident in Denmark at least one day from April 2, 1968 to November 4, 2005, or in Greenland from May 1, 1972 to November 4, 2005. A total of 8,176,097 persons were registered. On November 4, 2005, 5,427,687 (66.4%) were alive and resident in Denmark, 56,920 (0.7%) were alive and resident in Greenland, 2,141,373 (26.2%) were dead, 21,160 (0.3%) had disappeared, and 528,957 (6.5%) had emigrated. Among persons born in Denmark 1960 or later the CRS contains complete information on maternal identity. Among persons born in Denmark 1970 or later the CRS contains complete information on paternal identity. Among women born in Denmark April 1935 or later the CRS contains complete information on all their children. Among males born in Denmark April 1945 or later the CRS contains complete information on all their children. The CRS contains complete information on: a) immigrations and emigrations from 1971 onwards, b) permanent residence in a Danish municipality from 1971 onwards, c) permanent residence in a municipality in Greenland from May 1972 onwards, and d) full address in Denmark from 1977 onwards. Data from the CRS is an important research tool in epidemiological research, which enables Danish researchers to carry out representative population-based studies on e.g. the potential clustering of disease and death in families and the potential association between residence and disease and death.
    • There was also community recruitment using Web-based media, newspaper advertisements , and community presentations. In Denmark, the Danish National Register was used to identify individuals aged 90 years and above during the study recruitment period (Pedersen et al., 2006), and then archives were searched to locate the parents of the elderly individuals to identify potentially eligible sibships , who were then contacted regarding participation in the LLFS using criteria parallel to those used in the United States. Overall, 32.9% of the offspring generation was Danish.
    [Show abstract] [Hide abstract] ABSTRACT: Chromosomal telomere length shortens with repeated cell divisions. Human leukocyte DNA telomere length (LTL) has been shown to shorten during aging. LTL shortening has correlated with decreased longevity, dementia, and other age-associated processes. Because LTL varies widely between individuals in a given age group, it has been hypothesized to be a marker of biological aging. However, the principal basis for the variation of human LTL has not been established, although various studies have reported heritability. Here, we use a family-based study of longevity to study heritability of LTL in 3037 individuals. We show that LTL is shorter in older individuals, and in males, and has a high heritability (overall h(2) = 0.54). In the offspring generation, who are in middle-life, we find an ordinal relationship: persons more-closely-related to elderly probands have longer LTL than persons less-closely-related, who nonetheless have longer LTL than unrelated spouses of the offspring generation. These results support a prominent genetic underpinning of LTL. Elucidation of such genetic bases may provide avenues for intervening in the aging process. Copyright © 2015 Elsevier Inc. All rights reserved.
    Article · Jun 2015
    • Study participants were included between February and December 2013. The Danish Civil Registration System (DCRS) (Pedersen et al., 2006) assigns unique national identification numbers to all Danish residents by which individual demographic data including age, gender, current address, and information on immigration (including country of residence before immigration ) are recorded, making it possible to identify people with specific demographic characteristics. Participants were recruited based on a random sample of names and addresses obtained from the DCRS that later underwent telephone number enrichment, supplemented with a convenience sample of relatives and friends of bilingual research assistants and snowballing.
    [Show abstract] [Hide abstract] ABSTRACT: Older people from ethnic minorities are underrepresented in dementia care. Some of the determinants of access to care are knowledge and perceptions of dementia, which may vary between ethnic groups in the population. The aims of this study were to compare knowledge and perceptions of dementia and Alzheimer's disease (AD) among four ethnic groups in Copenhagen, Denmark, and to assess the influence of education and acculturation. Quantitative survey data from 260 participants were analyzed: 100 native Danish, and 47 Polish, 51 Turkish, and 62 Pakistani immigrants. Knowledge and perceptions of dementia and AD were assessed with the Dementia Knowledge Questionnaire (DKQ) supplemented with two questions from the Alzheimer's Disease Awareness Test (ADAT). Knowledge and perceptions of dementia and AD in the four groups were compared, and the influence of education and acculturation was assessed. Group differences were found on the DKQ total score as well as all sub-domains. Turkish and Pakistani people were most likely to hold normalizing and stigmatizing views of AD. Level of education and acculturation had limited influence on dementia knowledge, accounting for 22% of the variance at most and had only minor influence on perceptions of AD. Lacking knowledge and certain perceptions of dementia and AD may hamper access to services in some ethnic minority groups. Ongoing efforts to raise awareness that dementia and AD are not part of normal aging, particularly among Turkish and Pakistani communities, should be a high priority for educational outreach. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
    Article · Jun 2015
    • In 1968, the Danish Civil Registration System (CRS) was established . Since that time, every person living in Denmark or alive at the time the CRS was established has been assigned a CRS number (Pedersen et al., 2006). The CRS number serves as a unique personal identifier and enables linkage across all national registers.
    [Show abstract] [Hide abstract] ABSTRACT: Our aim was to characterize the incidence rates and cumulative incidence of anorexia nervosa (AN), bulimia nervosa (BN), and eating disorder not otherwise specified (EDNOS), and examine associations among eating disorder diagnoses, suicide attempts, and mortality. Individuals born in Denmark between 1989 and 2006 were included (N = 966,141, 51.3% male). Eating disorders diagnoses (AN, broad AN, BN, EDNOS) were drawn from the Danish Psychiatric Central Research Register (PCRR) and Danish National Patient Register (NPR). Suicide attempts and deaths were captured in the NPR, the PCRR, and the Danish Civil Registration System (CRS). In females, AN had a peak hazard at approximately age 15 years, BN at 22 years, and EDNOS had an extended peak that spanned 18 years-22 years. Eating disorder diagnoses predicted a significantly higher hazard for death and suicide attempt compared with the referent of individuals with no eating disorders. In males, peak hazard for diagnosis was earlier than in females. The present study represents one of the largest and longest studies of eating disorder incidence and suicide attempts and death in both females and males. Eating disorders are accompanied by increased hazard of suicide attempts and death even in young adults. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Article · Mar 2015
    • The Civil Registration System (CRS) was established in 1968. It contains data on vital status and residence for the entire Danish population (Pedersen et al. 2006). Thus, the CRS provides complete follow-up information on the entire study population.
    [Show abstract] [Hide abstract] ABSTRACT: Background and purpose Ceramic-on-ceramic (CoC) bearings were introduced in total hip arthroplasty (THA) to reduce problems related to polyethylene wear. We compared the 9-year revision risk for cementless CoC THA and for cementless metal-on-polyethylene (MoP) THA. Patients and methods In this prospective, population-based study from the Danish Hip Arthroplasty Registry, we identified all the primary cementless THAs that had been performed from 2002 through 2009 (n = 25,656). Of these, 1,773 THAs with CoC bearings and 9,323 THAs with MoP bearings were included in the study. To estimate the relative risk (RR) of revision, we used regression with the pseudo-value approach and treated death as a competing risk. Results 444 revisions were identified: 4.0% for CoC THA (71 of 1,773) and 4.0% for MoP THA (373 of 9,323). No statistically significant difference in the risk of revision for any reason was found for CoC and MoP bearings after 9 years of follow-up (adjusted RR = 1.3, 95% CI: 0.72–2.4). Revision rates due to component failure were 0.5% (n = 8) for CoC bearings and 0.1% (n = 6) for MoP bearings (p < 0.001). 6 patients with CoC bearings (0.34%) underwent revision due to ceramic fracture. Interpretation When compared to the “standard” MoP bearings, CoC THA had a 33% higher (though not statistically significantly higher) risk of revision for any reason at 9 years.
    Full-text · Article · Jan 2015
    • The study was based upon data from the Danish Psychiatric Central Research Register (Mors et al., 2011), the Civil Registration System (Pedersen et al., 2006), the Danish National Patient Register (Lynge et al., 2011), the Danish Medical Birth Registry (Knudsen and Olsen, 1998),
    [Show abstract] [Hide abstract] ABSTRACT: Background: The Danish Neonatal Screening Biobank, containing dried blood spot samples from all newborn in Denmark, is a unique source of data that can be utilized for analyses of genetic and environmental exposures related to schizophrenia and other mental disorders. In previous analyses, we have found that early and late blood sampling, compared to sampling at day 5, was associated with increased risk of schizophrenia. As delay in sampling of blood for neonatal screening cannot in itself influence the risk of schizophrenia, it must be seen as a proxy for unknown underlying causes responsible for this association. Therefore, we investigated whether the increased risk can be explained by other risk factors for schizophrenia. Methods: A case-control design was applied. A total of 846 cases with schizophrenia were selected from the Danish Psychiatric Case Register. One control was selected for each case, matched on sex and exact date of birth. Results: Both early and late blood sampling was associated with increased risk for schizophrenia. Compared to blood sampling at day 5, sampling at days 0 to 4 after birth was associated with an incidence rate ratio (IRR) of 1.46 (95% CI 1.15-1.87) for development of schizophrenia, and sampling at days 6 to 9 and at days 10 to 53 was associated with an IRR of 1.5 (95% CI 1.13-1.98) and 3.00 (95% CI 1.59-5.67), respectively. After adjusting the estimates for place of birth, both parents' psychiatric illness, maternal and paternal age, parents' country of origin, child admission, and parental education and income, the estimates were slightly different. Thus, blood collection at 0-4days was associated with an IRR of 1.27 (95% CI 0.94-1.71), 6-9days 1.31 (95% CI 0.94-1.84) and 10+days 3.52 (95% CI 1.50 to 8.24). Discussion: After adjusting risk estimates for well-known risk factors, delay in sampling of blood for neonatal screening was associated with unexplained increased risk of schizophrenia. Thus, a key finding is that age at test is a proxy for unobserved risk factors for schizophrenia due to unexplained reasons for late blood sampling. Date of sampling will be included in future analyses of genetic and environmental risk factors.
    Article · Jan 2015
    • We used data from the Danish Civil Registration System (CRS) (Pedersen et al., 2006) which was established in 1968 to obtain information on all residents alive and living in Denmark. It includes information on personal identification number, sex, date of birth, continuously updated information on vital status, and personal identification number of parents.
    [Show abstract] [Hide abstract] ABSTRACT: Different case definitions of schizophrenia have been used in register based research. However, no previous study has externally validated two different case definitions of schizophrenia against a wide range of risk factors for schizophrenia. We investigated hazard ratios (HRs) for a wide range of risk factors for ICD-10 DCR schizophrenia using a nationwide Danish sample of 2,772,144 residents born in 1955-1997. We compared one contact only (OCO) (the case definition of schizophrenia used in Danish register based studies) with two or more contacts (TMC) (a case definition of at least 2 inpatient contacts with schizophrenia). During the follow-up, the OCO definition included 15,074 and the TMC 7562 cases; i.e. half as many. The TMC case definition appeared to select for a worse illness course. A wide range of risk factors were uniformly associated with both case definitions and only slightly higher risk estimates were found for the TMC definition. Choosing at least 2 inpatient contacts with schizophrenia (TMC) instead of the currently used case definition would result in almost similar risk estimates for many well-established risk factors. However, this would also introduce selection and include considerably fewer cases and reduce power of e.g. genetic studies based on register-diagnosed cases only. Copyright © 2015 Elsevier B.V. All rights reserved.
    Article · Jan 2015
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