Improvement in energy and vitality over a short‐term CPAP trial predicts long‐term compliance in patients with obstructive sleep apnea

Patients with obstructive sleep apnea (OSA) have an impaired quality-of-life (QoL) that improves with continuous positive airway pressure (CPAP) therapy (Bennett et al., 1999; D Ambrosio et al., 1999). The most severely affected QoL domain is that for energy and vitality (EV), in keeping with a clinical picture of sleepiness as a dominant symptom in OSA (Ballester et al., 1999). While the short-term effects of CPAP therapy on EV have been well documented (Ballester et al., 1999; Engelman et al., 1994; Montserrat et al., 2001), the long-term benefits have not been well described, and it is not known whether these early benefits of CPAP therapy are maintained over a longer period of time. Moreover, factors that are predictive of improved compliance with CPAP therapy have not been clearly established, and the value of short-term EV improvements as a predictor of the long-term compliance with CPAP therapy is unknown. We studied the impact of a 2-week CPAP trial on the change in EV over the trial and 1-year follow-up, and its relationship with compliance with CPAP therapy at 1 year, in 82 patients referred to our unit with OSA in whom CPAP therapy was indicated based on typical symptoms and overnight oximetry recording. The optimal CPAP pressure selected, after manual titration on at least two occasions during the 2-week titration trial, was the minimum pressure that abolished snoring and normalized oxygen desaturations. EV was assessed by the Medical Outcomes Study Short Form 36 (SF-36) questionnaire, that was completed by patients before and after the CPAP trial and at 1-year follow-up, where compliance with CPAP therapy was also calculated by reading the counter. Patients were classified as compliers if their average nightly CPAP use was >4 h at 1 year. Otherwise they were classified as non-compliers . It is important to note that the choice of a 4 h cut-off for compliance was arbitrary, and does not define the difference between clinically useful compliance and noncompliance. We studied 69 men and 13 women, mean age 53 years (standard deviation 10), and mean body mass index (BMI) 36 kg m (7). No differences in age, sex, or BMI were observed between compliers and non-compliers before the trial, and BMI remained constant in both groups for the duration of the study. There was no difference in the optimal CPAP pressure selected between compliers (n = 41), 8.7 cm H2O (2) and non-compliers (n = 41) 8.0 cm H2O (2; P = NS). While both groups used CPAP for >4 h per night during the trial, compliers used it more, 6 h (2) than non-compliers, 4.5 h (3; P < 0.001). While there was no difference in baseline EV scores between compliers 27.3 (3.6) and non-compliers 37.1 (3.4; P = 0.05), and no difference in post-trial EV scores between compliers 59.4 (3.9) and noncompliers 50.6 (3.6; P = 0.1), the magnitude of improvement in EV over the CPAP trial was significantly greater in the complier group 32.1 (5.4) compared to the non-complier group 13.5 (3.9; P = 0.007; Table 1). This improvement in EV was maintained at 1 year in the complier group 54.8 (3.8), but not the non-complier group 42.9 (3.7; P = 0.02; Table 1), and at 1 year follow-up compliers used CPAP for longer, 7 h (1.6) per night compared with non-compliers, 1.5 h (1.3; P < 0.0001). Moreover, we found agreement between the change in EV over the CPAP trial and longterm compliance (r = 0.28, P = 0.03). These findings suggest that the extent of improvement in EV scores from baseline over a 2-week CPAP trial may be a useful additional early predictor of long-term compliance with CPAP therapy in patients with OSA. However, a larger and more detailed study is needed to confirm these preliminary findings. An area for further research would be to determine whether the magnitude of improvement in QoL scores over a CPAP trial is a more useful tool for predicting long-term compliance. Table 1 SF-36 mean (SEM) energy and vitality (EV) scores at baseline, after a 2-week CPAP trial, and at 1-year follow-up in compliers (n = 41) and non-compliers (n = 41) with CPAP therapy