1. Chydenius Institute, Jyväskylä University, Kokkola, Finland and National Research and Development Centre for Welfare and Health, Health Services Research Unit, Helsinki, Finland,
2. Institute of Gerontology and School of Public Health, University of Michigan, Ann Arbor, Michigan, USA and Ann Arbor VA Medical Center, Ann Arbor, Michigan, USA
3. National Research and Development Centre for Welfare and Health, Health Services Research Unit, Helsinki, Finland
4. Department of Public Health, University of Helsinki, Finland and Medical Management Centre, Karolinska Institutet, Stockholm, Sweden