a cohort of 886 cases of multiple sclerosis ( ms ) who had onset between jan 1 , 1960 , and dec 31 , 1969 , and who were resident in 1970 in either a low-prevalence area ( los angeles county , california , 560 cases ) or in a high-prevalence area ( king and pierce counties , washington , 326 cases ) were followed up for changes in disability status through dec 31 , 1979 .
C3829255
los angeles county
C0006754
california