The Swedish Twin Registry: Content and Management As a Research Infrastructure
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Twin Research and Human Genetics (2019), 1–9 doi:10.1017/thg.2019.99 Article The Swedish Twin Registry: Content and Management as a Research Infrastructure Ulrika Zagai, Paul Lichtenstein, Nancy L. Pedersen and Patrik K. E. Magnusson Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden Abstract The Swedish Twin Registry functions as research infrastructure containing information on 216,258 twins born between 1886 and 2015, of whom 86,199 pairs have zygosity determined by DNA, an intrapair similarity algorithm, or being of opposite sex. In essence, practically all twins alive and currently 9 years or older have been invited for participation and donation of DNA on which genomewide single nucleotide polymorphisms array genotyping has been performed. Content, management and alternatives for future improvements are discussed. Keywords: Twin; registry; biobank; population-based; Sweden; genetics; environment (Received 19 May 2019; accepted 31 May 2019) The Swedish Twin Registry (STR) was established in the late 1950s specific range of birth years (Table 1). Here, we describe these to investigate the role of environmental factors such as smoking and efforts in the chronological order of when data collection was alcohol on disease. Since then, the STR has developed into an infra- conducted (finished). structure of broad utility, with the mission to provide a longitudinal resource for epidemiological and molecular studies of twins. Q61, 63, 67, 70 — The first compilation (same-sex twins born Content of the STR in 1886–1925). During the end of the 1950s, all Swedish parishes were contacted and asked to deliver details of all church book The last overview article about the STR was published in TRHG in records of same-sex multiple births between 1886 and 1925. The 2013 (Magnusson et al., 2013). In this update, we provide a twin births were followed through to 1947 when the system of summary of the major, so-called base-data collections, structured unique personal numbers for each citizen living in Sweden according to the source of data: (1) Self- or parental responses was introduced. Because the initial aims focused on the health to questionnaires/interviews, (2) biobanking, (3) genotyping, effects of smoking and alcohol, the birth years were restricted to (4) biomarkers, (5) health check-ups and (6) national register 1886–1925, which generated a suitable age span at risk, of linkages. ~35–75 years, at the beginning of the 1960s (Cederlöf, 1966). Stemming from the base-data, there have been several ancillary All identified twins received the so-called ‘green questionnaire’ studies directed toward specific phenotypic or geographic selec- in 1960, but unfortunately only the answers from pairs in which tions, conducted by various users over the years. Sometimes, the both twins responded were saved (N = 21,990). The same selection data collected in such studies have been fed back into the STR data- of twins received follow-up questionnaires in 1963 (red question- base and may, therefore, be open for secondary use. However, naire) and 1967 (blue questionnaire). In 1970, a complementary because of their heterogeneity and incomplete coverage, we do questionnaire was sent to twins who did not respond or who not describe them further here. Thus, the description is limited had missing information about alcohol or tobacco in 1967. The to include only nationwide efforts to collect data with a broad scope. requested information in all these questionnaires was about sim- ilarity (for zygosity), demographic, medical and lifestyle aspects Self- or Parental Responses (Lichtenstein et al., 2002). Between 1960 and 2005, the STR was almost exclusively a collection of phenotypic and exposure data and most resources Q73 — The second compilation (same-sex twins born in were put into obtaining responses to questionnaires or inter- – views. Several large efforts to gather this type of data have been 1926 1958). A new twin cohort was compiled in 1973 by using made throughout the history of the STR, each directed toward a national registrations of births from 1926 to 1967. Identified same-sex twin-pairs born in 1926–1958 in which both were alive Author for correspondence: Patrik K. E. Magnusson, Email: [email protected] and living in Sweden were sent a questionnaire with content Cite this article: Zagai U, Lichtenstein P, Pedersen NL, and Magnusson PKE. The similar to that given to the older cohorts. Individual responses were Swedish Twin Registry: Content and Management as a Research Infrastructure. Twin obtained from 36,536 participants (Lichtenstein et al., 2002). Research and Human Genetics https://doi.org/10.1017/thg.2019.99 © The Author(s) 2019. This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives licence (http:// creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is unaltered and is properly cited. The written permission of Cambridge University Press must be obtained for commercial re-use or in order to create a derivative work. Downloaded from https://www.cambridge.org/core. Karolinska Institutet University Library, on 26 Nov 2019 at 08:20:31, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/thg.2019.99 2 Ulrika Zagai et al. Table 1. Questionnaire or interview data in nationwide STR base-studies Acronym Years Birth cohort Focus Selection N (Indiviuals) Q 61, 63, 70 1960–1970 1886–1925 Health and exposures Same-sex, complete pairs 21,890 Q 73 1973 1926–1958 Health and exposures Same sex 36,536 SALT 1998–2002 1944–1958 Health older adults No 45,000 TwinGene 2004–2008 <1943 CVD, RA, Diabetes SALT participants 14,598 SALTY 2009 <1958 Economic behavior, health SALT participants 11,743 STAGE 2004–2006 1959–1985 Health in adulthood No 25,484 YATSS 2013 1985–1992 Health in young adulthood No 6870 CATSS 2004– >1992 Neurodevelopment, asthma, allergy No 32,570 Screening Across the Lifespan Twin Study (SALT) — all twins provide a blood sample and have their blood pressure, height born 1958 or earlier. A large nationwide effort to contact all and weight measured at their local healthcare facility. Out of available twins, including for the first time, opposite-sex pairs, 22,000 twins invited, close to 14,600 (65%) responded to the ques- was conducted between 1998 and 2002 (Lichtenstein et al., 2002; tionnaire. Cardiovascular diseases were covered with questions Pedersen et al., 2002). The project involved extensive data collec- about the occurrence and year of onset for angina pectoris, coro- tion conducted over the telephone by trained interviewers. If nary infarct, hypertension, high cholesterol or high triglycerides, self-response was not possible or if the twin performed poorly claudication, venous thrombosis, stroke or blood clot and transient on a short mental status screen conducted on all twins 65 years ischemic attacks. Cardiac bypass or angioplastic surgery and heart old or older, informants such as spouse or relatives were inter- medications were also recorded. Questions about diabetes included viewed. The data collection consisted of similarity questions used type of diabetes and diabetes medication and whether (and when) for the zygosity algorithm and questions about the amount of or not a medical doctor had established the diagnosis. Further, contact with co-twin, demographics (including occupation and questions about pain, migraine or recurring headache, knee or education), checklist of common diseases, use of prescribed and hip arthrosis and rheumatoid arthritis were asked. For rheumatoid nonprescribed medications, health behaviors (physical activity, arthritis, follow-up questions included whether or not a medical alcohol and tobacco consumption) and permission to collect medi- doctor had established the diagnosis, if the subject went to regular cal records. By using branching with detailed follow-up questions check-ups because of the condition and whether medication for to participants who responded positively to initial key items, the arthritis besides pain remedy was used (Magnusson et al., 2013; specificity of disease screening was improved for a number of Rahman et al., 2009). disorders. The selection of items for each disease domain was done in collaboration with experts in each field, with an intended aim to SALTY (extended questionnaire to younger subjects in use recognized and established instruments whenever available. SALT). The SALTY study was a collaborative effort between When the data collection for the SALT study was ended in STR and researchers in epidemiology, medicine, political science 2002, 44,919 twins had participated. and economics. The target population was the younger part of the SALT cohort born between 1943 and 1958. The data collection Study of Twin Adults: Genes and Environment (STAGE), all began in the fall of 2008 by sending an extensive questionnaire to twins born in 1958–1985. During 2005 and 2006, the STR con- 24,914 Swedish twins, and it was completed in the summer of 2010. tacted twins born in Sweden 1958–1985 with an invitation letter The survey generated a total of 11,647 responses (47%). Out of to respond to a web-based survey (this was the first attempt to these, 11,482 (98.6%) respondents gave informed consent to have collect data by a web-based interphase; Furberg, Lichtenstein, their responses stored and analyzed.