Subjective sleep quality in cystic fibrosis

Abstract

Objectives: To evaluate sleep quality in patients with cystic fibrosis (CF).

Methods: The Pittsburgh Sleep Quality Index (PSQI) questionnaire was administered to 37 CF patients with moderate to severe lung disease in a clinically stable state. Sleep studies were performed concurrently. PSQI scores were correlated with results of anthropometric variables, arterial blood gas tensions, lung function variables, and polysomnographic variables. Potential differences in objective measurements between patients with high and low scores on the PSQI were assessed.

Results: Thirty-seven patients with CF were studied, aged 27+/-8 (mean+/-1 SD) years and forced expiratory volume in 1 s (FEV(1)) 36+/-12% predicted. The mean PSQI was 5.7+/-4.0. Fourteen of the 37 patients had a high PSQI, i.e. >5. Significant correlations between objective variables and both component scores and total PSQI were as follows: age and 'subjective sleep quality' (r=0.4, P<0.05), age and 'sleep duration' (r=0.3, P<0.05), FEV(1) % predicted and 'subjective sleep quality' (r=-0.4, P<0.05), carbon monoxide transferred per litre of lung volume (KCO) % predicted and 'daytime dysfunction' (r=-0.4, P<0.01), PaCO(2) and 'sleep latency' (r=0.4, P<0.01), arterial carbon dioxide tension (PaCO(2)) and 'habitual sleep efficiency' (r=0.3, P<0.05), PaCO(2) and total PSQI (r=0.4, P<0.05), absolute minimum sleep oxyhemoglobin saturation by pulse oximetry (SpO(2) %) and 'sleep latency' (r=-0.4, P<0.05), absolute minimum sleep SpO(2) % and 'sleep duration' (r=-0.4, P<0.05), absolute minimum sleep SpO(2) % and total PSQI (r=-0.4, P<0.05) and awake transcutaneous CO(2) and 'sleep duration' (r=0.45, P<0.05). Better sleep efficiency (P<0.05) and a greater % of rapid eye movement (REM) sleep (P<0.05) were found in those patients with a PSQI of < or =5.

Conclusions: A number of CF patients reported poor sleep quality. A relationship was shown between subjective sleep quality and physiological variables describing disease severity. Better sleep efficiency and % REM sleep were seen in patients with low PSQI scores. These results suggest a useful role for the PSQI in assessing sleep quality in patients with CF.