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Electronic Appendix
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3
(eAppendix)
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Registry data
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Since 1968, all Danish residents have been registered in the Central Population Register and
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assigned a unique personal identification number, which ensures accurate linkage of
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information among all national registries (e1). We obtained information on cohabitation
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status, vital status, and emigration status from the Central Population Register.
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Cancer diagnosis
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Information on cancer diagnoses were obtained from the Danish Cancer Register (e2). Tumors
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were classified according to a modified Danish version of the International Classification of
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Diseases, 10th revision (ICD-10) (e3).
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Cohabitation
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Cohabitation was included because, in Denmark, more than 20% of all couples living together
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in 2002 were unmarried (e4). We defined cohabitation as two unmarried persons of the
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opposite sex, over the age of 16 years, with a maximum age difference of 15 years, who had
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lived together for at least 5 years, with no other adults in the household.
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Education
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The educational level of the men was obtained from the population-based Integrated Database
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for Labor Market Research at Statistics Denmark, which contains yearly data since 1980 (e5,
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e6).
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Morbidity
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Information on morbidity was obtained from the Danish National Patient Register which
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includes the dates of admission and discharge and diagnoses coded according to modified,
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national versions of the ICD-8 (e3) or, from 1994, ICD-10 (e7). On the basis of recorded
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hospital contacts, we defined the Charlson comorbidity index (e1,e8), grouped according to
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the cumulated sum of scores of 0, 1–2 and ≥ 3. This index provides an overall score for
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comorbidity on the basis of a composite of values weighted by level of severity (score, 1–6)
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assigned to 19 selected conditions (e1,e8). A score of 1 included myocardial infarct,
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congestive heart failure, peripheral vascular disease, cerebrovascular disease, dementia,
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chronic pulmonary disease, connective tissue disease, ulcer disease, mild liver disease,
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diabetes type 1 and diabetes type 2. A score of 2 included hemiplagia, moderate-to-severe
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renal disease, and diabetes type 1 or 2 with end-organ damage. A score of 3 included
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moderate-to-severe liver disease, while a score of 6 included AIDS.
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(e1) Dalton SO, Schüz J, Engholm G, et al. Social inequality and incidence of and survival
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from cancer in a population–based study in Denmark, 1994–2003: background, aims,
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material and methods. Eur J Cancer 2008; 44: 1938–1949.
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(e2) Storm HH, Michelsen EV, Clemmensen IH, et al. The Danish Cancer Registry—history,
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content, quality and use. Dan Med Bull 1997; 44: 535–539.
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(e3) World Health Organization. International classification of diseases. Manual of the
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international statistical classification of diseases, injuries, and causes of death. 10th rev.
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Geneva, World Health Organization, 1992.
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(e4) Official website of Denmark: www.denmark.dk (accessed 6 April 2012).17.World
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(e5) Eurostat/Statistics Denmark. Statistics on persons in Denmark: a register–based
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statistical system. Brussels, Office for Official Publications of the European Communities,
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1995.
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(e6) Thygesen L. The register-based system of demographic and social statistics in
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Denmark—an overview. Stat J UN Econ Commun Eur 1995; 12: 49–55.
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(e7) World Health Organization. International classification of diseases. Manual of the
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international statistical classification of diseases, injuries, and causes of death. 8th rev.
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Geneva: World Health Organization, 1967.
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(e8) Charlson ME, Pompei P, Ales KL, et al. A new method of classifying prognostic
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comorbidity in longitudinal studies: development and validation. J Chron Dis 1987; 40: 373–
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383.