Key points are not available for this paper at this time.
1Centre for Epidemiology, National Board of Health and Welfare, SE-106 30 StockholmSweden. Tel:+46 8 5555 3000. Fax; +46 8 5555 3327. E-mail: gudrun.persson@sos.se, Etc., 2Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden. Tel:+46 8 517 779 71. E-mail: finn.diderichsen@socmed.ki.se, 3National Institute of Health, SE-103 52 Stockholm, Sweden. Tel:+46 8 5661 3515. E-mail: bosse.pettersson@fhi.se, 4Department of Public Health &Clinical Medicine, UmeaE university, SE-90 185 UmeaE , Sweden. Tel:+46 90 785 1209. E-mail. stig.wall@epiph.umu.se
Persson et al. (Sat,) studied this question.