1. Department of Research Cancer Registry of Norway PB 5313 Majorstuen Oslo N‐0304 Norway
2. Oslo centre for biostatistics and epidemiology Oslo University Hospital Pb 4950 Nydalen Oslo 0424 Norway
3. Oslo Ischemia study Oslo University Hospital Oslo Norway
4. Department of Public Health and General Practice Norwegian University of Science and Technology PB 8905 Trondheim 7491 Norway