MASS-EX: Expert-Annotated Dataset for Interpretable Sleep Staging

MASS-EX (Montreal Archive of Sleep Studies — EXpert annotations) is an expert-annotated dataset built upon the MASS SS3 subset. For each 30-second polysomnography (PSG) epoch, it provides a sleep stage label, applicable AASM rule identifiers, and—for a fine-annotated subset—a full expert-written rationale describing the clinical reasoning behind the staging decision. The dataset comprises 62 subjects and 59,193 annotated epochs (5,006 with full rationale, 54,187 with rule identifiers only), covering five sleep stages (W, N1, N2, N3, R) and a library of 15 AASM-based scoring rules. This dataset contains annotations only; the underlying PSG signals must be obtained separately from the MASS repository.