Validation of a questionnaire to screen for shift work disorder

Abstract

Study objective: At least 15% of the full-time work force is shift workers. Working during the overnight hours, early morning start times, and variable or rotating schedules present a challenge to the circadian system, and these shifts are associated with adverse health and safety consequences. Shift work disorder (SWD), a primary (circadian rhythm) sleep disorder indicated by excessive daytime sleepiness and/or insomnia associated with a shiftwork schedule, is under-recognized by primary care physicians. We sought to develop and validate a questionnaire to screen for high risk of SWD in a shift working population.

Design: Shift workers completed a 26-item questionnaire and were evaluated by a sleep specialist (physician) who diagnosed them as either positive or negative for SWD. The physician assessment of SWD was guided by a flow chart that operationalized the ICSD-2 criteria for SWD.

Setting: 18 sleep clinics in the USA.

Patients or participants: 311 shift workers.

Interventions: Not applicable.

Measurements and results: Responses to the items in the questionnaire were entered into a series of discrimination function analyses to determine the diagnostic value of the items and the fewest number of questions with the best predictive value. The function was then cross-validated. A final 4-item questionnaire has 89% positive predictive value and 62% negative predictive value (sensitivity = 0.74; specificity = 0.82).

Conclusions: This Shiftwork Disorder Screening Questionnaire may be appropriate for use in primary care settings to aid in the diagnosis of SWD.

Figure 1

A diagnostic flow chart was developed with assistance from accredited sleep physicians in a focus group. It was distributed to the sleep clinics where study participants were clinically evaluated in order to standardize the diagnosis of shift work disorder. Shift work is defined as non-standard shift schedule (starts before 7am or after 2pm, rotates, or regularly includes hours outside of the standard 7am to 6pm work day). Insomnia is defined as difficulty going to sleep, staying asleep or having refreshing sleep, 3 or more times per week, for at least one month. Excessive sleepiness is defined as inability to function due to sleepiness.

Figure 2

The scree plot visually confirms the function has 6 components, 1 of them being a major component.