The Danish Conscription Database - DCD

The steering group of the Danish Conscription Database welcomes collaboration and the interest of national and international colleagues.
If you have any questions regarding the database, please contact Gunhild Tidemann Okholm or Merete Osler.

In order to access the database please submit the research protocol to project leader Erik Lykke Mortensen.

Once the project has been approved a collaboration agreement must be completed. The database will subsequently be made available upon final approval by the steering committee with permission from relevant data inspection authorities.

The establishment of the Danish Conscription Database (DCD)

The DCD was established in 2008-2013 by digitizing selected information from the Danish conscript board register cards. The conscript board examinations have been conducted according to national guidelines and the information collected has been recorded in a standardized format in register cards from the mid 1950’ies through 1986 and from then on the information collected has been stored electronically. In 1957 an intelligence test was implemented in the conscript board examination, and from 1957 through 1978 the information was uniformly measured. In 1979 the educational registration was altered, while the registration of the other data remained the same.

The funding was insufficient to digitize all of the available register cards. Moreover, the organization of the cards made it difficult to delimitate to either year of conscript board examination or year of birth. It was decided to digitize complete archive units, so that the majority of men from the 21 birth cohorts from 1939-1959 was included, because these men would predominantly have been examined in the period from 1957 through 1978 in which the data was uniformly measured. In the database the two outer birth cohorts, 1939 and 1959, are not as complete as the intermediate cohorts, as some of the men’s cards were located in archival units that were not digitized.

Who is in the cohort?

All Danish men are requested at age 18 to appear before the conscript board and only a small percentage is exempted due to medical conditions. Boys volunteering for military service before their 18th birthday are also exempted from appearing. In the DCD the exempts are registered with personal identification details and no examination data from the conscript board.

To assess the completeness of the database the birth cohorts from the database was compared with the number of men from the corresponding birth cohorts in the Statistical Yearbook. For the years 1940 to 1958, the coverage rate is 81.2% to 95.2%, while the coverage rate is lower for the years 1939 and 1959 due to the regional disparities in the archiving of register cards (see figure). Furthermore, register cards from the reunited southern part of Jutland (district 7/see map) for the birth cohort 1952-1954 were lost due to a flooding.

Variables in the database

The selected variables to be digitized were: identifying information (either name, date of birth and place of birth/ address when at conscript or personal identification number (CPR-number)), conscript board district (see map), time of conscript board examination (the year and half-year), height (measured without shoes), weight (measured with underwear), educational level, and intelligence test score (9 categories).

The intelligence test comprises four subtests which assess the logical, verbal, numerical and spatial abilities, and has been administered uniformly in the period from 1957 and up to today. For a more detailed description of each variable see list of variables.

Identification of CPR-numbers

A total of 741.636 unique conscript register cards were digitized. About 70% of the men were registered with a CPR-number and the vast majority of these men could be linked directly to the CPR-register. The remaining 30% attended the conscript board before the introduction of CPR-numbers in 1968, and hence were only registered by name and date of birth. A custom made matching program was used to identify the CPR-number for these 30% by matching name and date of birth from the register cards with name and date of birth from the CPR-register. In total 728.160 (98,2 %) of the entered men were identified in the CPR-register, and this population constitutes the database

Erik Lykke Mortensen
(Chairman and Principal investigator)
Professor, MSc in Psychology
Section of Environmental Health
Institute of Public Health
University of Copenhagen
Copenhagen
Denmark
Direct: +45 3532 7839
Email: elme@sund.ku.dk

Merete Osler Professor
DMSc, PhD
Center for Clinical Research and Prevention Bispebjerg and Frederiksberg Hospitals
Frederiksberg
Denmark
Direct: +45 3816 3100
Email: merete.osler@regionh.dk
Mobile: +45 4010 4312

Kaare Christensen
Professor, Dr.Med.Sci PhD
Danish Ageing Research Center
Institute of Public Health
University of Southern Denmark
Odense
Denmark Direct: +45 6550 3049
Email: kchristensen@health.dk

Thorkild IA Sørensen
Professor, dr.med.sci.
Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen and
Section of Epidemiology, Institute of Public Health, University of Copenhagen
Copenhagen
Denmark
Direct:+45 9356 5934
Email: tias@sund.ku.dk

Gunhild Tidemann Okholm
Senior researcher, PhD, MSc
National Institute of Public Health
University of Southern Denmark
Copenhagen
Denmark
Direct: +45 6550 7770
Email: gunh@sdu.dk                                                

Terese Sara Høj Jørgensen
Associate professor, PhD, Msc
Section of Social Medicine
Institute of Public Health
University of Copenhagen
Copenhagen
Denmark
Direct: +45 3533 5886
Email: tshj@sund.ku.dk

The DCD has been described and documented in the Cohort Profile: The Danish Conscription Database (DCD)

So far data from the DCD has been applied in studies concerning the topics of obesity, metabolism, risk of diseases and cognitive ability. For instance Christensen et al 2016 (Christensen et al 2016) have found an inverse association between intelligence assessed at the conscript board and mortality from natural and unnatural (accidents, suicide, and homicide) causes. Data have also been included in large scale international population studies of trends in height (NCD-RisC Height) and weight (NCD-RisC Weight)

Publications with data from the Danish Conscription Database (February 2019):

1. Grønkjær M, Osler M, Flensborg-Madsen T, Sørensen HJ, Mortensen EL. Associations between education and age-related cognitive changes from early adulthood to late midlife.Psychology and Aging. Accepted and in press 2019
   
   
2. Hegelund ER, Flensborg-Madsen T, Dammeyer J & Mortensen El. Low IQ as a predictor of unsuccessful educational and occupational achievement: A register-based study of 1,098,742 men in Denmark 1968-2016. Intelligence. 71:46-53, 2018
   
   
3. Nissen LR, Karstoft KI, Vedtofte MS, Nielsen ABS, Osler M, Mortensen EL, Christensen GT, Andersen SB. Low-level cognitive ability in young adulthood and other risk factors of depression in an observational cohort study among deployed Danish soldiers. Soc Psychiatry Psychiatr Epidemiol. Jan 2019
   
   
4. Osler M, Christensen GT, Mortensen EL, Christensen K, Garde E, Rozing MP.Hearing loss, cognitive ability, and dementia in men age 19-78 years. Eur JEpidemiol. 2018 Oct
   
   
5. Christensen GT, Rozing MP, Mortensen EL, Christensen K, Osler M. Young adult cognitive ability and subsequent major depression in a cohort of 666,804 Danish men. J Affect Dis. April 2018
   
   
6. Christensen GT, Skogstad S, Nissen LR, Osler M. Data resource profile: Danish Conscription Registry Data (DCRD). Int J Epidemiol. April 2018
   
   
7. Osler M, Rozing MP, Christensen GT, Andersen PK, Jørgensen MB. Electroconvulsive therapy and risk of dementia in a cohort of 168 015 patients with affective disorders. Lancet Psych 2018: 5:348-353.

8. Wüst M, Mortensen EL, Osler M, Sørensen TIA. Universal infant health interventions and young adult outcomes. Health Econ. Aug 2018
   
   
9. Jensen BW, Bjerregaard LG, Ängquist L, Gögenur I, Renehan AG, Osler M, Sørensen TIA, Baker JL. Change in Overweight from Childhood to Early Adulthood and Risk of Type 2 Diabetes Int J Obes (Lond). Oct 2018
   
   
10. Bjerregaard LG1, Jensen BW, Ängquist L, Osler M, Sørensen TIA, Baker JL. Change in Overweight from Childhood to Early Adulthood and Risk of Type 2 Diabetes. N Engl J Med. 2018 Apr 5;378(14):1302-1312
    
    
11. Osler M, Mortensen EL, Christensen K, Christensen GT. A bidirectional association between cognitive ability in young adulthood  and epilepsy: A population based cohort study. Int J Epidemiol 2018 Epub Feb 12.
    
    
12. NCD Risk Factor Collaboration (NCD-RisC)*. Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416population-based measurement studies in 128•9 million children, adolescents, and adults. Lancet. Oct. 2017
    
    
13. Nissen LR, Karstoft KI, Vedtofte MS, Nielsen ABS, Osler M, Mortensen EL,Christensen GT, Andersen SB. Cognitive ability and risk of post-traumatic stress disorder after military deployment: an observational cohort study. BJPsych Open. 2017 Nov 8;3(6):274-280.
    
    
14. Christensen, G.T., et al., The influence of familial factors on the intelligence-mortality association – A twin approach. Intelligence, 2017. 64: p. 60-66.
    
    
15. Osler, M., et al., Cognitive ability in young adulthood and risk of dementia in a cohort of Danish men, brothers, and twins. Alzheimers Dement, 2017.
    
    
16. Jørgensen TSH, Osler M, Ängquist LH, Zimmermann E, Christensen GT, Sørensen TIA. The U-shaped association of body mass index with mortality: influence of the traits height, intelligence and education. Obesity Sept 2016, doi:10.1002/oby. 21615.
    
    
17. Christensen GT, Mortensen EL, Christensen K, Osler M. Intelligence in young adulthood and all-cause and cause specific mortality in the Danish Conscription Database- a cohort study of 728,160 men.Intelligence Epub 23 August 2016.
    
    
18. NCD Risk factor collaboration (NCD-RisC)* A century of trends in adult human height: pooled analysis of 1,472 population-based measurement studies with 19,2 million participants. Elife, Epub 26 July 2016.
    
    
19. Aarestrup J, Bjerregaard L, Gamborg M, Ängquist L, Tjønneland A, Overvad K, Linneberg A, Osler M, Mortensen EL, Gyntelberg F, Lund R, Sørensen TIA, Baker J.Tracking of body mass index from 7 to 69 years of age. Int J Obes 2016, 28 June.
    
    
20. NCD Risk factor collaboration (NCD-RisC)* The weight of the World-trends in adult body mass index in 200 countries since 1975: pooled analysis of 1,698 population-based measurement studies with 19,2 million participants. The Lancet 2016;387:1377-96.
    
    
21. Christensen GT, Molbo M, Ängquist LH, Mortensen EL, Christensen K, Sørensen TIA, Osler M. Cohort profile: The Danish Conscription Database (DCD). A cohort of 728 160 men born from 1939 through 1959 and examined by the conscript board in the period from 1957 through 1984. Int J Epidemiol 2015;44:432-40.