Development and evaluation of the Indian Sleepiness Scale to assess excessive daytime sleepiness in patients with Obstructive Sleep Apnea.

Background: Excessive daytime sleepiness (EDS), a cardinal symptom of obstructive sleep apnea (OSA) is assessed using Epworth Sleepiness Scale (ESS). Some limitations of ESS include graded responses, inapplicable situations and equal scores for active and passive situations. To overcome these limitations, we developed a novel sleepiness scale and evaluated its performance in patients with OSA.

Methods: The study was executed in multiple phases. After determining applicability of items in the ESS, a 6-item questionnaire was developed comprising OSA symptoms and self-reported 'sleepy' situations, dichotomized responses and weighted scoring. After content and face validation by experts, the scale was tested for applicability and its performance was compared with ESS in patients with suspected OSA.

Results: In phase I, applicability of ESS was tested in 189 participants, of whom 98 (51.8 %) participants found multiple items inapplicable.In phase II, 34 self-reported sleepy situations from 200 participants were narrowed down to a 6-item questionnaire, based on expert validation. This scale was named the Indian Sleepiness Scale (ISS) and was tested for applicability in phase III in 226 participants from diverse literacy backgrounds, who found all situations applicable.In phase IV, ISS and ESS were administered to 335 patients with suspected OSA. OSA was confirmed on polysomnography in 294 (87.7 %) patients. A cut-off score of ≥6 was derived for ISS; at this cut-off score, the ISS which was more sensitive than ESS (71.1 % vs 43.2 %).

Conclusions: The Indian Sleepiness Scale was found to be widely applicable and more sensitive than ESS for sleepiness evaluation in patients with OSA.