title: In patients with minimally symptomatic OSA can baseline characteristics and early patterns of CPAP usage predict those who are likely to be longer-term users of CPAP.
abstract: BACKGROUND
  Long-term continuous positive airway pressure (CPAP) usage varies between individuals. It would be of value to be able to identify those who are likely to benefit from CPAP (and use it long term), versus those who would not, and might therefore benefit from additional help early on. First, we explored whether baseline characteristics predicted CPAP usage in minimally symptomatic obstructive sleep apnoea (OSA) patients, a group who would be expected to have low usage. Second, we explored if early CPAP usage was predictive of longer-term usage, as has been shown in more symptomatic OSA patients.
  
  
  METHODS
  The MOSAIC trial was a multi-centre randomised controlled trial where minimally symptomatic OSA patients were randomised to CPAP, or standard care, for 6 months. Here we have studied only those patients randomised to CPAP treatment. Baseline characteristics including symptoms, questionnaires [including the Epworth sleepiness score (ESS)] and sleep study parameters were recorded. CPAP usage was recorded at 2-4 weeks after initiation and after 6 months. The correlation and association between baseline characteristics and 6 months CPAP usage was assessed, as was the correlation between 2 and 4 weeks CPAP usage and 6 months CPAP usage.
  
  
  RESULTS
  One hundred and ninety-five patients randomised to CPAP therapy had median [interquartile range (IQR)] CPAP usage of 2:49 (0:44, 5:13) h:min/night (h/n) at the 2-4 weeks visit, and 2:17 (0:08, 4:54) h/n at the 6 months follow-up visit. Only male gender was associated with increased long-term CPAP use (male usage 2:56 h/n, female 1:57 h/n; P=0.02). There was a moderate correlation between the usage of CPAP at 2-4 weeks and 6 months, with about 50% of the variability in long-term use being predicted by the short-term use.
  
  
  CONCLUSIONS
  In patients with minimally symptomatic OSA, our study has shown that male gender (and not OSA severity or symptom burden) is associated with increased long-term use of CPAP at 6 months. Although, in general, early patterns of CPAP usage predicted longer term use, there are patients in whom this is not the case, and patients with low initial usage may need to extend their CPAP trial before a decision about longer-term use is made.
authors.affiliation: 1 Oxford Centre for Respiratory Medicine, Oxford University Hospitals NHS Trust, Oxford, UK ; 2 Oxford Biomedical Research Centre, National Institute for Health Research, Oxford, UK ; 3 Department of Pulmonology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Turnbull
authors.affiliation: 1 Oxford Centre for Respiratory Medicine, Oxford University Hospitals NHS Trust, Oxford, UK ; 2 Oxford Biomedical Research Centre, National Institute for Health Research, Oxford, UK ; 3 Department of Pulmonology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Bratton
authors.affiliation: 1 Oxford Centre for Respiratory Medicine, Oxford University Hospitals NHS Trust, Oxford, UK ; 2 Oxford Biomedical Research Centre, National Institute for Health Research, Oxford, UK ; 3 Department of Pulmonology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Sonya E
authors.initials: SE
authors.lastname: Craig
authors.affiliation: 1 Oxford Centre for Respiratory Medicine, Oxford University Hospitals NHS Trust, Oxford, UK ; 2 Oxford Biomedical Research Centre, National Institute for Health Research, Oxford, UK ; 3 Department of Pulmonology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Kohler
authors.affiliation: 1 Oxford Centre for Respiratory Medicine, Oxford University Hospitals NHS Trust, Oxford, UK ; 2 Oxford Biomedical Research Centre, National Institute for Health Research, Oxford, UK ; 3 Department of Pulmonology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: John R
authors.initials: JR
authors.lastname: Stradling
keywords: Obstructive sleep apnoea (OSA); continuous positive airway pressure (CPAP); patient compliance