Morten Frisch1,2, Jacob Simonsen3. 1. Department of Epidemiology Research, Statens Serum Institut, 2300, Copenhagen S, Denmark. mfr@ssi.dk. 2. Department of Clinical Medicine, Center for Sexology Research, Aalborg University, 9000, Aalborg, Denmark. mfr@ssi.dk. 3. Department of Epidemiology Research, Statens Serum Institut, 2300, Copenhagen S, Denmark.