Cross-cultural adaptation and construct validity of the Portuguese version of the Bordeaux Sleepiness Scale (BOSS): A cross-sectional study in patients with sleep disorders

Background Excessive sleepiness while driving is a public safety concern. The Bordeaux Sleepiness Scale (BOSS) is a brief patient-reported measure designed to assess driving-related sleepiness. However, a Portuguese version is not currently available.Objective To cross-culturally adapt the BOSS and evaluate its internal consistency and construct validity in a Portuguese population, in accordance with COSMIN recommendations.Study design and methods We conducted a cross-sectional observational study of adults attending a Sleep Disorders Clinic. The BOSS was translated into Portuguese following a standardised cross-cultural adaptation process. Participants completed the Portuguese BOSS, the Epworth Sleepiness Scale (ESS) and two questions assessing driving-related sleepiness. Internal consistency was evaluated using Cronbach’s alpha. Construct validity was assessed through Spearman correlations with the ESS (convergent validity) and by comparing scores between participants with and without a history of sleepiness-related accidents or near-misses (criterion-related validity). ROC curve analysis further assessed criterion validity.Results A total of 234 patients were included; 94.4% had obstructive sleep apnoea and 9.4% reported sleepiness-related accidents or near-misses in the previous year. The BOSS demonstrated moderate internal consistency (α = 0.683) and acceptable accuracy in identifying patients with sleepiness-related events (AUC = 0.895), compared with the ESS (AUC = 0.842). Both scales showed significantly higher scores in participants with sleepiness-related accidents or near-misses than in those without (p < 0.001). A moderate correlation with ESS (ρ = 0.551, p < 0.001) was observed.Conclusion The Portuguese BOSS shows moderate internal consistency and evidence of construct validity. These findings provide preliminary support for its use in identifying driving-related sleepiness in patients with sleep disorders.