Introduction Severity of OSA and early patterns of CPAP usage have previously been shown to determine subsequent long term CPAP use in patients with symptomatic moderate-to-severe disease.1 We wished to see if different factors influenced compliance in minimally symptomatic patients.
Methods Patients were randomised to 6-months of CPAP or standard care if they had an ODI of >7.5 h due to OSA on a baseline sleep study, but had insufficient daytime OSA symptoms to mandate CPAP.2
Baseline characteristics (Table 1), medical history, ESS, SAQLI and SF-36 were recorded. Repeat overnight pulse oximetry was performed after entry for uniformity of trial ODI across recruiting centres.
CPAP usage data were downloaded at the 2–4 week assessment, and at the 6 month assessment. Those who withdrew were assumed to have 0:00 h/n usage.
Correlations were calculated between CPAP usage at the 6 month assessment and both the baseline characteristics and to the 2–4 week CPAP usage data.
Results Median CPAP usage at 2–4 week follow-up was low at 2:49 h/n (n = 174, IQR 0:44, 5:13). Median usage at 6 month follow-up was 2:17 h/n (n = 195, IQR 0:08, 4:54).
At 6 months males had significantly greater mean usage at 2:56 h/n compared to 1:47 h/n in females (95% confidence intervals of the difference, -1:49 to -0:09 h/n, p = 0.02). There were no other significant predictors of 6 month usage (age, BMI, ODI, ESS, sleep symptoms, smoking status, ethnicity, SAQLI, SF-36).
Average usage of CPAP at 2–4 week assessment was moderately correlated with the average usage at the 6 month assessment (r = 0.76, p < 0.001).
Conclusions Male gender predicted greater CPAP usage at 6 months, but no other baseline characteristics were predictive of CPAP usage in these minimally symptomatic patients with generally mild OSA. 2–4 week CPAP usage was predictive of 6 month usage, but by no means could all patients’ usage be predicted at such an early stage. Thus in clinical practice, trials of CPAP are necessary in patients with minimally symptomatic OSA but it may be necessary for patients to try CPAP for longer than one month to determine those benefitting from treatment in the long term.
References 1 Thorax 2010;65:829–32
2 Thorax 2012;67:1090-66