Ethnic Disparities in CPAP Adherence in New Zealand: Effects of Socioeconomic Status, Health Literacy and Self-Efficacy

Study Objectives: We aimed to investigate the influence of ethnicity on adherence with continuous positive airway pressure (CPAP) in a sample of New Zealand patients. Design: Observational study over one month. Setting: A university-based sleep laboratory. Patients: 126 consecutively consenting CPAP-naive patients (19.8% Maori, mean +/- SD apnea-hypopnea index 57.9 +/- 38.9 events/h, CPAP 11.1 +/- 3.1 cm H2O). Interventions: Patients underwent a 4-week supervised home trial of CPAP following pressure titration. Measurements and Results: Self-identified ethnicity (Maori/non-Maori), Epworth Sleepiness Scale, Self-Efficacy Measure for Sleep Apnea, Rapid Estimate of Adult Literacy in Medicine, New Zealand Deprivation Index (calculated from residential address), New Zealand Individual Deprivation Index (validated 8-item questionnaire), educational history, income, and employment assessed at baseline were compared to objective CPAP adherence after one month. Maori demonstrated significantly lower usage than non-Maori (median 5.11, interquartile range 2.24 h/night compared with median 5.71, interquartile range 2.61 h/night, P = 0.05). There were no significant relationships between adherence and subjective sleepiness, health literacy, or self-efficacy. In a multivariate logistic regression model incorporating 5 variables (ethnicity, eligibility for government-subsidized healthcare, individual deprivation scores, income, and education), non-completion of tertiary education, and high individual socioeconomic deprivation remained significant independent predictors of average CPAP adherence not reaching >= 4 h (odds ratio 0.25, 95% CI 0.08-0.83, P = 0.02; odds ratio 0.10, 95% CI 0.02-0.86, P = 0.04, respectively). The overall model explained approximately 23% of the variance in adherence. Conclusions: The disparity in CPAP adherence demonstrated between Maori and non-Maori can be explained in part by lower education levels and socioeconomic status.