Cohort profile update: the Danish HIV Cohort Study (DHCS).

The DHCS is a cohort of all HIV-infected individuals seen in one of the eight Danish HIV centres after 31 December 1994. Here we update the 2009 cohort profile emphasizing the development of the cohort. Every 12-24 months, DHCS is linked with the Danish Civil Registration System (CRS) in order to extract an age- and sex-matched comparison cohort from the general population, as well as cohorts of family members of the HIV-infected patients and of the comparison cohort. The combined cohort is linked with CRS, the Danish Cancer Registry, the Danish National Hospital Registry, the Danish Registry of Causes of Death, the Danish National Prescription Registry, the Attainment Register and the Integrated Database for Labour Market Research to get information on vital status, migration, cancer, hospital contacts, causes of death, dispensed prescriptions, education and employment. Using this design, rates of a range of outcomes have been compared between HIV-infected patients and the comparison cohort, as well as between families of these two cohorts in order to disaggregate the effects of HIV infection and familial/environmental factors. Data can be shared with foreign institutions following approval from the Danish Data Protection Agency. Potential collaborators can contact the study director, Niels Obel (e-mail: niels.obel@regionh.dk).