Objective
Sleep health has evolved from focusing on specific disorders, such as insomnia and sleep apnea, to a broader perspective that includes regularity, efficiency, and socio-environmental influences. Psychological flexibility, particularly the acceptance process, has been identified as a key protective factor for sleep health. Therefore, assessing acceptance of sleep difficulties is essential for both research and clinical practice, as it provides insights into adaptive coping and informs interventions. The Sleep Problem Acceptance Questionnaire (SPAQ) is the only validated instrument for assessing acceptance of sleep difficulties, making it a valuable tool for interventions based on Acceptance and Commitment Therapy (ACT). This study aimed to adapt the SPAQ for Brazilian Portuguese, ensuring both semantic and psychometric equivalence.

Methods
The adaptation process included translation, back-translation, expert review, and pilot testing. The final version was validated in a sample of 1,352 participants, including individuals with insomnia and healthy controls.

Results
Confirmatory factor analysis supported the original two-factor structure (Activity Engagement and Willingness) with good model fit indices. We found evidence for stability of measurement properties across 14 days, but inconclusive evidence regarding the structural invariance between groups of good and poor sleepers. Reliability was high for both factors. Convergent validity was confirmed, showing negative correlations between acceptance and insomnia severity, psychological inflexibility, anxiety, and depression.

Conclusion
The Brazilian adaptation of the SPAQ shows adequate psychometric properties and is a valuable tool for clinicians and researchers. However, caution is needed when comparing scores across groups of good and bad sleepers, as item-level differences may affect structural comparability.