Calculation of WPAI questionnaire outcomes.
| Outcome | Equation* |
|---|---|
| Percentage of work time missed because of health | Q2/(Q2 + Q4) for those who were currently employed |
| Percentage of impairment while working because of health | Q5/10 for those who were currently employed and actually worked in the previous 7 days |
| Percentage of overall work impairment due to health | Q2/(Q2 + Q4) + ((1 − Q2/(Q2 + Q4)) × (Q5/10)) for those who were currently employed |
| Percentage of activity impairment due to health | Q6/10 for all respondents |
↵* Results expressed in percentages by multiplying each score by 100. WPAI: Work Productivity and Activity Impairment; Q: question; Q1: currently employed; Q2: hours missed due to health problems; Q3: hours missed for other reasons; Q4: hours actually worked; Q5: degree that health affected productivity while working (using a 0–10 Likert scale); Q6: degree that health affected productivity in regular unpaid activities (0–10 Likert scale).