Social class and chronic illness.
D000041:Absenteeism; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001294:Attitude to Health; D002908:Chronic Disease; D004185:Disability Evaluation; D006306:Health Surveys; D006801:Humans; D007182:Income; D008875:Middle Aged; D044469:Racial Groups; D012923:Social Class; D014481:United States