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Absence is easy to measure. Someone is either at work or they are not. The Work Productivity and Activity Impairment questionnaire exists because that measurement misses most of what ill health actually costs, which happens on the days people come in anyway and get through perhaps two thirds of a day.
In short
- Developed by Reilly, Zbrozek and Dukes, published in 1993 in PharmacoEconomics.
- Six questions, all covering the past seven days.
- Produces four percentages: absenteeism, presenteeism, overall work impairment, and activity impairment.
- The fourth score covers unpaid activity, which most productivity instruments ignore completely.
- Adapted into versions for specific conditions, and used widely in clinical trials.
The problem it was built for#
Occupational health research spent decades measuring absenteeism, because absenteeism is countable. Then a run of studies established something awkward: for most chronic conditions, the productivity lost while people are at work substantially exceeds the productivity lost to their being away.
This is presenteeism. Migraine, depression, arthritis, allergy and chronic pain rarely stop someone attending. They stop someone concentrating, sustaining effort, handling a difficult conversation, or finishing what they started, none of which appears in an attendance record.
Turning up is not the same as being able to work, and only one of the two is easy to count.
The six questions#
The instrument is unusually short. One item establishes whether the person is employed at all, three ask for hours, and two ask for a rating from 0 to 10.
| Item | What it asks |
|---|---|
| 1 | Whether you are currently employed |
| 2 | Hours missed because of your health |
| 3 | Hours missed for any other reason |
| 4 | Hours actually worked |
| 5 | How much your health affected your productivity while working, from 0 to 10 |
| 6 | How much your health affected your regular unpaid activities, from 0 to 10 |
Item 6 is the one worth pausing on. It asks about regular daily activities outside paid employment: housework, shopping, childcare, study, exercise, caring for a relative. It is answered by everyone, including people with no job at all, which is why the instrument still returns something meaningful for a full-time carer.
How it is scored#
The four outputs are all percentages, and a higher number always means more impairment.
| Score | How it is derived |
|---|---|
| Absenteeism | Work time missed: item 2 divided by (item 2 plus item 4) |
| Presenteeism | Impairment while working: item 5 divided by 10 |
| Overall work impairment | Absenteeism and presenteeism combined |
| Activity impairment | Impairment in unpaid activity: item 6 divided by 10 |
The percentage framing is what carried the instrument beyond clinical research. It converts a health state into a figure that fits on a spreadsheet, which is what allowed the cost of untreated conditions to be argued in terms employers respond to.
There is a general health version, usually written WPAI:GH, and a long list of versions adapted to specific conditions, which is how the instrument came to be so common in clinical trials.
Limits worth knowing#
- Self-assessed productivity is imprecise. People are not reliable estimators of their own output, in either direction.
- A 0 to 10 rating is blunt. Presenteeism is the larger component of the total for most conditions, and it rests on a single number from a single question.
- Seven days is a short window. It suits a trial checkpoint better than it suits a condition that runs in longer cycles.
- It asks respondents to attribute cause. Each item requires separating the effect of health from everything else going on that week, which is a judgement people are not well placed to make.
- Employer framing shapes answers. The same person answers differently depending on who they believe is reading.
Who the measurement is for#
Worth being clear-eyed about the lineage. This class of instrument was built to quantify what a worker's health costs an employer, and that is not hidden: the headline output is a productivity-loss percentage, and the audience for that figure has usually been the organisation rather than the person who filled the form in.
It is also what made the approach effective. Converting a health state into a number that appears on a spreadsheet is what got employers to fund treatment for conditions they had previously ignored, and a great many people benefited from that.
It explains the sharpest limitation too. Someone who suspects their answers will reach a manager has every reason to under-report. A measure of how much work is costing you and a measure of how much you are costing your employer look identical on paper, and they are not the same question.
Any self-report instrument is partly a measure of who the respondent thinks is listening.
Common questions#
- What is the Work Productivity and Activity Impairment questionnaire?
- The WPAI is a six-item instrument measuring how much a health problem affected a person's work and daily activities over the past seven days. It produces four percentages: absenteeism, presenteeism, overall work impairment, and activity impairment. It was published by Reilly, Zbrozek and Dukes in 1993.
- What is presenteeism?
- Presenteeism is reduced productivity while a person is at work, as opposed to absenteeism, which is productivity lost to being away. For many chronic conditions, presenteeism accounts for a larger share of total lost productivity than absence does.
- What does the WPAI activity impairment score measure?
- Activity impairment is the percentage by which a health problem affected regular daily activities outside paid employment over the past seven days, such as housework, shopping, childcare, study, exercise or caring for a relative. It is answered by everyone, including people who are not employed, which is why the instrument still returns a meaningful result for a full-time carer.
- How does the WPAI differ from the Work Limitations Questionnaire?
- Both measure productivity loss from health problems. The WPAI has six items, covers the past seven days, and reports four percentages, one of which covers unpaid activity. The Work Limitations Questionnaire has 25 items across four scales and focuses on categories of job demand, such as time management and output.
immli is a wellbeing and understanding tool, not a medical service. Questions about this page go to hello@immli.me.
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