Quality of life was assessed with the disease-specific Calgary sleep apnea quality of life index,18–19 which has been shown to be a highly responsive tool for measuring quality of life in patients with sleep apnea.19 It assesses four domains: daily functioning, social interactions, emotional functioning, and symptoms. For each domain, patients answer a series of questions (for daily functioning, n = 11 questions; social interactions, n = 13; emotional functioning, n = 11; and symptoms, the patient chooses the five most troublesome symptoms from a list of potential symptoms). Each question has seven response options. Mean scores for each domain are calculated by summing the total score and dividing by the number of questions. For the total score, the sums of the four mean domain scores are divided by four. After treatment, treatment-related side effects or symptoms are also assessed (the patient chooses the five most troublesome from a long list of potential side effects). Treatment-related side effects or symptoms scores are then summed (after recoding) and divided by five. Treatment-related side effects are then weighted by calculating global impact scores (positive and negative). To obtain the total score after treatment, the four domain scores are summed and then the weighted side effect score is subtracted, and then the total is divided by four.19Subjective sleepiness was assessed with the Epworth sleepiness scale.20The Epworth sleepiness scale is a self-administered questionnaire in which patients are asked to score the likelihood of falling asleep during eight different sedentary situations with different levels of stimulation. Patients estimate their likelihood of falling asleep on a 4-point scale, from 0 = never falling asleep during this situation, to 3 = high probability of falling asleep. Scores are summed to yield an overall total, which can range from 0 to 24. A score of 0 to 10 is within the normal range, while a score > 12 suggests excessive subjective sleepiness.21 At study entry, patients were asked whether they experienced 12 nasal symptoms on a regular basis.13 Patients answered yes or no for each symptom. CPAP side effects were assessed using a self-administered questionnaire13 and by sections E and F of the Calgary sleep apnea quality of life index. With the CPAP side effect questionnaire, patients were asked to rate the following potential adverse side effects: pressure from mask or straps, air leak from mask, air leak from mouth, machine noise, cold face or nose, claustrophobia, dry mouth or throat, running nose, congested nose, dry nose, nose bleeds, headache, difficulty breathing, chest discomfort, mask coming off face, skin irritation, and air pressure being too much. Patients rated each effect as follows: 0 = not a problem; 1 = slight problem but did not interfere with using CPAP; 2 = moderate problem, sometimes CPAP could not be used; and 3 = major problem, CPAP could often not be used. Measurements were obtained at baseline (except for CPAP compliance and side effects) and at 1 month, 3 months, and 12 months.