Which questionnaire instruments are valid for detecting lighting intervention effects on workplace wellbeing and performance?

A lighting questionnaire has to catch a small, reversible shift

A lighting intervention usually changes how people feel and perform by a modest amount, and the change appears and disappears with exposure. An instrument is useful here if it is sensitive enough to register that shift, not just good at describing a stable trait. In the night-shift study, the same workers moved between traditional lighting and brighter, bluer lighting across nights, and the Karolinska Sleepiness Scale picked up a difference: the worsening of sleepiness across the shift was smaller under the intervention, with a partial eta-squared of 0.14, a statistic where larger values mean the lighting explained more of the variation in scores [4]. That is the kind of within-person sensitivity a lighting study needs.

The same study shows why one instrument is not enough. Subjective mood ratings did not differ between the two lighting conditions, even though alertness and performance did [4]. A questionnaire battery built only around mood would have concluded the intervention did nothing. The choice of instrument therefore decides what counts as an effect.

Alertness and performance: the best-supported pairing

The clearest evidence for detecting a lighting effect comes from combining a subjective sleepiness scale with an objective performance task. In rotating night shift workers, the Karolinska Sleepiness Scale and the Psychomotor Vigilance Task, a timed reaction test, both showed improvement in the middle and end of the shift under brighter, blue-enriched light compared with traditional lighting [4]. The performance task added something the questionnaire could not: mean reaction time and the number of lapses, meaning reactions slower than 500 milliseconds, improved with partial eta-squared values of 0.19 and 0.17 respectively [4].

This matters for interpreting questionnaire results. Self-reported alertness and measured vigilance moved in the same direction, which strengthens the case that the lighting change was real rather than a matter of expectation. The study was small, 28 workers, mostly male, in one chemical plant, so the size of the effect should not be assumed to transfer directly to a typical office [4].

Office studies point the same way but with less detail. A blue-enriched white light study in offices used questionnaires and rating scales to assess alertness, mood, sleep quality and performance across two four-week exposure periods [3], and a survey of office lighting assessed alertness, comfort, satisfaction, safety and performance using questionnaires alongside objective measures [1]. Neither abstract names the instruments or reports whether they were validated, so they support the general approach of measuring alertness and performance together but cannot confirm a specific tool.

Wellbeing is broader than sleepiness, and the tools are less settled

Workplace wellbeing in these studies is usually split into separate, concrete outcomes rather than one wellbeing score: comfort, satisfaction, safety, mood, tension, and sleep quality [1][3][4]. In the night-shift study, subjective tension, misery and depression all worsened over the course of the night, but none of them differed between lighting conditions [4]. That is a useful distinction for anyone choosing instruments: a scale can be sensitive to time of day and still be insensitive to lighting.

For a new workplace lighting intervention, one research programme describes using an occupational survey to evaluate effects, explicitly framing it as a measure of response to a workplace-lighting intervention rather than a clinical diagnostic instrument, and noting that measurement performance in this new application context still needs to be established [2]. In plain terms, the survey is being adapted for the job rather than already proven at it. That is the honest state of the field: established scales exist for alertness and vigilance, while broader wellbeing measurement in lighting studies is often assembled case by case.

What this means if you are designing or judging a study

If the goal is to detect a lighting effect on performance and alertness, the Karolinska Sleepiness Scale paired with a vigilance task has the most direct support, having detected a real difference between lighting conditions in a repeated-measures field study [4]. Add separate ratings for mood and comfort rather than relying on a single combined wellbeing score, because mood did not track the lighting change even when alertness did [4].

Be cautious about treating any single named questionnaire as validated for lighting. The office studies describe questionnaire and rating-scale batteries covering alertness, comfort, satisfaction, safety and performance [1][3], and the newer protocol describes an occupational survey whose measurement performance in this context is still being worked out [2]. None of these abstracts reports a formal validation of a lighting-specific instrument. A study that reports which scales it used, and shows they moved with the intervention, is giving you more than one that simply says questionnaires were administered.

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