“…Those who answered “yes” to these consecutive questions were considered to have work-related headaches and eyestrain. Demographic variables included sex, age (< 30, 30–39, 40–49, 50–59, and ≥ 60 years), education (less than a high school diploma and more than a college degree), income level (1st, 2nd, 3rd, and 4th quintile), occupation (managers, professionals, and office workers), work hours (< 40 hours, 40–52 hours, and > 52 hours), workplace size (small [1–49 workers], medium [50–299 workers], and large [≥ 300 workers]), 8 sleep disorder status, and use of electronic devices such as computers during work hours. For sleep disorder status, the Minimal Insomnia Symptom Scale was utilized to assess respondents’ answers to the items “difficulty in initiating sleep,” “difficulty in maintaining sleep,” and “non-restorative sleep,” with a score of 0 for “never,” 1 for “less often,” 2 for “several times a month,” 3 for “several times a week,” and 4 for “daily.” If the sum of the three items was 6 or more, the respondent was considered to have a sleep disorder.…”