title: Association between duration of daily VDT use and subjective symptoms.
abstract: BACKGROUND
  Although visual display terminal (VDT) work has become a common task among office workers, surveys which would help to determine the allowable duration of daily VDT use are limited.
  
  
  METHODS
  We investigated more than 25,000 workers three times over a 3-year period using a self-administered questionnaire. Three factors, namely mental, physical and sleep-related symptoms, were extracted by factor analysis. Adjusted means of each factor score were compared with the duration of daily VDT use by general linear model.
  
  
  RESULTS
  Physical symptoms score became higher with increasing duration of daily VDT use without a threshold effect. Mental and sleep-related symptom scores of the workers using VDT for more 5 hr/day were significantly higher than that of the groups using VDT for >1, 1-3, and 3-5 hr/day.
  
  
  CONCLUSIONS
  Duration of daily VDT use was linearly related to the physical symptom score, and was non-linearly related to mental and sleep-related symptom score with a threshold effect of 5 hr/day.
authors.affiliation: Department of Occupational and Environmental Medicine, Graduate School of Medicine, Chiba University, Chiba, Japan. ookubo@med.m.chiba-u.ac.jp
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Nakazawa
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Okubo
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Suwazono
authors.forename: Etsuko
authors.initials: E
authors.lastname: Kobayashi
authors.forename: Shingo
authors.initials: S
authors.lastname: Komine
authors.forename: Norihisa
authors.initials: N
authors.lastname: Kato
authors.forename: Koji
authors.initials: K
authors.lastname: Nogawa
mesh_terms: D000328:Adult; D018771:Arthralgia / Q000209:etiology; D001248:Asthenopia / Q000209:etiology; D016288:Computer Terminals; D005221:Fatigue / Q000209:etiology; D006261:Headache / Q000209:etiology; D006801:Humans; D017116:Low Back Pain / Q000209:etiology; D001523:Mental Disorders / Q000209:etiology; D008875:Middle Aged; D009784:Occupational Diseases / Q000150:complications* / Q000209:etiology* / Q000523:psychology; D020069:Shoulder Pain / Q000209:etiology; D007319:Sleep Initiation and Maintenance Disorders / Q000209:etiology; D011795:Surveys and Questionnaires; D013997:Time Factors