Abstract
Objective:
To assess obstructive sleep apnea (OSA) severity, continuous positive airway pressure (CPAP) adherence, and factors associated with CPAP adherence among a group of patients with OSA receiving care at a publicly funded county hospital.
Study Design and Setting:
A retrospective cohort study in a 464-bed urban public hospital in Cook County, Illinois.
Results:
A total of 507 patients were included. They had a mean (SD) age of 46.9(11) years, mean body mass index of 46.2 (11.0) kg/m2; mean and median baseline apnea-hypopnea index (AHI) of 71.0 (44.4) and 69.5 episodes/h; mean Epworth Sleepiness Scale (ESS) score of 15.8 (6.1). Of these patients, 53% were men, 74% did not have health insurance coverage, and 77% were African American. Mean CPAP adherence of the 323 patients with follow-up data was 3.87 (2.62) hours/day, with 47.7% of subjects using CPAP objectively for ≥4 hours/day. Women were 2.49 (95% CI, 1.39–4.46) times more likely to be nonadherent than men, after adjusting for race, marital status, and age. Of the 172 patients who did not follow up, there were disproportionately more men. When individuals without follow-up were assumed to be nonadherent, the overall compliance rate was 30.4%, and women were 1.72 (95% CI, 1.03–2.88) times more likely to be noncompliant than men, adjusting for race, marital status, and age.
Conclusion:
This study population experienced severe OSA. CPAP adherence was low, with women having a higher likelihood of nonadherence than men. With the epidemic of obesity and increased awareness of OSA, this population should be further studied to diminish future health disparities in the treatment of this disease.
Citations:
Joo MJ; Herdegen JJ. Sleep apnea in an urban public hospital: Assessment of severity and treatment adherence. J Clin Sleep Med 2007;3(3):285–288
Keywords: Sleep-disordered breathing, severity of disease, urban population, treatment adherence
Obstructive sleep apnea (OSA) is a condition characterized by repetitive episodes of breathing cessation during sleep due to upper airway obstruction. The primary risk factor for OSA is obesity with other prominent risk factors being increasing age and male gender.
OSA is a common disease in the United States affecting over 12 million people. A Wisconsin cohort study estimated the prevalence of OSA to be 2% in women and 4% in men ages 30 to 60.1 Symptoms of OSA include excessive daytime sleepiness, cognitive dysfunction, and diminished quality of life. Complications associated with OSA include systemic arterial hypertension,2–4 cardiac problems,5–8 cerebrovascular accidents,5,9 insulin resistance and diabetes mellitus,10–12 accidental death due to cognitive impairment,13–15 and death.16
Minority populations, in particular African Americans, demonstrate a much higher prevalence of obesity compared to whites.17–19 African Americans also have a higher prevalence than whites of cardiovascular risk factors, including hypertension and diabetes mellitus.20–22 Based on these trends and previous studies, the prevalence of sleep disordered breathing in this population may also be higher.23,24 Greenberg et al. compared patients from a voluntary hospital and city hospital-based minority serving institution (MSI) and found that the MSI patients had a greater body mass index, more comorbid medical conditions, and lower minimum sleep oxygen saturation. Forty-two percent of the MSI patients diagnosed with OSA failed to follow up for treatment, compared with 7% in the voluntary hospital group.25
Continuous positive airway pressure (CPAP) is an effective first line therapy for OSA, along with lifestyle modifications, leading to reduction of symptoms and improvement in cognitive function and quality of life.26 However CPAP therapy may not be well tolerated, and few studies have specifically focused on the pattern and treatment adherence of OSA in low-income minority urban populations. The urban patient population studied by Kribbs et al. had an adherence rate of 46%, when regular use was defined by at least 4 hours of CPAP a day; the sample size, however, was relatively small.27
The purpose of this study was to assess OSA severity, CPAP adherence, and factors associated with CPAP adherence among a group of patients with OSA receiving care at a publicly funded county hospital.
MATERIALS AND METHODS
This study was approved by the Institutional Review Board at the University of Illinois At Chicago.
Subject Identification
Subjects were cared for at Cook County Hospital (currently John H. Stroeger Jr. Hospital of Cook County) by the physicians and staff from the Rush-Presbyterian-St. Luke's Sleep Disorders Center. The clinic was part of a joint venture between the hospitals.
Patients seen at the Cook County Sleep Clinic underwent an initial evaluation and subsequent polysomnography (PSG), if recommended by the physician. The diagnosis of OSA required an apnea/hypopnea index >5 per hour on the PSG. An obstructive apnea was defined as cessation of nasal-oral airflow lasting at least 10 seconds with evidence of continuous respiratory effort. An obstructive hypopnea was defined as a reduction in nasal-oral airflow lasting at least 10 seconds, accompanied by either a 4% reduction in oxygen saturation without an arousal or a reduction in oxygen saturation of less than 4% followed by an arousal. An arousal was defined as 3 consecutive seconds of alpha waves on the central leads of the electroencephalography. The AHI was calculated as the number of apneas and hypopneas per hour of total sleep time and was scored according to the recommendations of the American Academy of Sleep Medicine.28 Patients with OSA received a CPAP machine and training and were given an appointment for a follow-up visit one month later. Subjects were enrolled from July 1999 and followed to April 2004. Patients included in this analysis were those who met the diagnostic criterion of OSA, received a CPAP machine and training, and were given a follow-up appointment date.
Polysomnography and CPAP machine
A standard 12-channel polysomnogram at the Rush-Presbyterian-St. Luke's Sleep Disorders Center was used for all patients. The electromyogram, electrooculogram, and electroencephalogram leads were applied according to the international 1020 electrode placement system. CPAP machines and training were provided by 2 durable medical equipment companies who agreed to participate under a fee-for-service program where the patients were educated and provided equipment in the outpatient sleep clinic. CPAP compliance machines with a microchip from either Respironics® or Resmed® were provided to all patients. CPAP compliance data was downloaded from the microchips and converted to an Excel® format by the physician and nurse practitioner.
Statistical Analysis
The means and standard deviations of normally distributed continuous variables were compared using the two-tailed Student's t test. Ordinal and categorical variables were compared using a Chi-square test or Fisher's exact test. The apnea hypopnea index (AHI) did not fulfill the assumption of normality; therefore, a square root transformation of AHI was used. All p-values <0.05 were considered significant. All analyses were performed using SAS (SAS release 8.02). A multiple logistic regression model was used to determine odds ratios.
Outcome Measures
CPAP use of less than 4 hours/day averaged over 30 days was considered noncompliant. The following factors were evaluated as predictors for CPAP noncompliance: age, race, sex, marital status, baseline apnea-hypopnea index (AHI), Epworth Sleepiness Scale (ESS), and insurance status.
Sensitivity Analysis
In order to better understand the robustness of our findings, a sensitivity analysis was done to understand the impact of the individuals who did not follow up. Significant findings during the analysis of the individuals who followed up and provided adherence data were repeated with the inclusion of the individuals who did not follow up. In this sensitivity analysis, we assumed the individuals who did not follow up were nonadherent to CPAP therapy.
RESULTS
Between July 1999 and April 2004, 507 patients diagnosed with OSA documented by PSG received CPAP machines. As shown in Table 1, hypertension and diabetes mellitus were self-reported in 61% and 25% of this study group, respectively. The mean (SD) age of the 507 subjects was 46.9(11) years; 52.7% were male. Seventy-seven percent of subjects self-reported themselves as African American, and 74% did not have health insurance coverage. The mean degree of OSA was severe, with a mean apnea-hypopnea index (AHI) of 71.0 (44.4) episodes per hour and a median of 69.5 episodes per hour. The average body mass index (BMI) was 46.2 (11.0) kg/m2 with 100% of patients being obese based on Centers for Disease Control (CDC) guidelines (BMI ≥30 kg/m2).
Table 1.
Demographics and Baseline Characteristics of Cohort.*
| Patient Number | 507 |
| Male patients, % | 52.7% |
| Race | |
| African American | 77% |
| Hispanic | 15% |
| Caucasian | 6% |
| Asian/Pacific Islander | 2% |
| Comorbidities,% | |
| Diabetes | 25% |
| Hypertension | 61% |
| Married, % | 25% |
| Age, y | 46.9 (11.9) |
| Body Mass Index, kg/m2 | 46.2 (11.0) |
| 71.0 (44.4) | |
| Apnea-Hypopnea Index (AHI), | Median 69.5 |
| Number of events per hour | Minimum 5.3 |
| Maximum 199.0 | |
| No insurance coverage, % | 74% |
| Epworth Sleepiness Scale score | 15.8 (6.1) |
Data presented as mean (SD) unless otherwise stated.
Of the 507 patients, 335 presented for the follow-up appointment and provided CPAP adherence data. Of the 335 patients, 323 had adequate CPAP adherence data for analysis. Mean CPAP use was 3.87 (2.62) hours/day with 47.7% of subjects using CPAP objectively for ≥4 hours/day averaged over 30 days. Sex and race were the only independent variables found to be significantly associated with CPAP nonadherence. The results in Table 2 show that women were 1.57 (95% CI, 1.01–2.44) times more likely to be nonadherent than men. Women were 2.49 (95% CI, 1.39–4.46) times more likely to be nonadherent than men after adjusting for race, marital status, and age (Table 2).
Table 2.
CPAP Nonadherence and Sex.
| Variable | Covariate | OR | 95% CI |
|---|---|---|---|
| Female | 1.57 | (1.01–2.44) | |
| Female | Race | 1.94 | (1.17–3.23) |
| Female | Marital status | 1.76 | (1.10–2.84) |
| Female | Age | 1.77 | (1.11–2.81) |
| Female | Race, Marital status | 2.19 | (1.27–3.77) |
| Female | Race, Age | 2.28 | (1.33–3.91) |
| Female | Marital Status, Age | 2.00 | (1.20–3.32) |
| Female | Race, Marital status, Age | 2.49 | (1.39–4.46) |
When individuals without follow-up were assumed to be nonadherent, the overall adherence rate was 30.4% and women were 1.72 (95% CI, 1.03–2.88) times more likely to be nonadherent than men, adjusting for race, marital status, and age.
African Americans were 5.02 (95% CI, 1.59–15.84) times more likely to be nonadherent than Caucasians (Table 3). However, this finding may be biased because of the small number of Caucasians compared with African Americans (196 African Americans versus 18 Caucasians). There were also small numbers of subjects who were categorized as Hispanic and Asian/Pacific Islander. The odds of nonadherence were not significant when comparing any other ethnic groups.
Table 3.
CPAP Nonadherence and Race.
| Variable | Covariate | OR | 95% CI |
|---|---|---|---|
| African American | 5.02 | (1.59–15.84) | |
| African American | Sex | 4.26 | (1.33–13.62) |
| African American | BMI | 6.37 | (1.77–22.94) |
| African American | Sex, BMI | 5.51 | (1.51–20.09) |
DISCUSSION
This study describes the patient demographics and poor adherence to the treatment of sleep disordered breathing in a population cared for at an urban public hospital. Treatment adherence was low in patients who followed up and were included in the analysis; however, this is likely an overestimation of the overall adherence of CPAP considering the lack of follow-up in patients diagnosed with this disease. When individuals without follow-up were assumed to be nonadherent, the overall adherence rate was only 30.4%.
OSA is a common disease in the United States, and the overall prevalence based on diagnostic criteria is thought to be greatly underestimated. Minorities have a higher prevalence of obesity and medical comorbidities and therefore likely a higher OSA prevalence. There are serious and life-threatening complications associated with OSA and adherence to treatment is imperative. In this predominantly minority and largely uninsured cohort of patients receiving care at a publicly funded county hospital, women and African Americans were more likely to be nonadherent than men and Caucasians, respectively. Since the majority of this population is African American, the relationship between these two races, although significant, is questionable as evidenced by the wide confidence interval. A study involving a larger Caucasian population for comparison will be needed to elucidate whether this difference truly exists.
The 172 subjects who did not follow up is a limitation in this study. Among the non–follow-up group, smaller proportions were women and married individuals compared with the follow-up group, creating potential selection bias (Table 4). However, when the analysis was repeated assuming the non–follow-up group to be nonadherent, women were still more likely to be nonadherent compared to men, after adjusting for race, marital status, and age. The reason for the low adherence in this cohort is not clear. We had limited data on income and true socioeconomic status based on income and total number of family members. Lack of social support systems may have been a contributing factor. Women in this cohort may be of lower socioeconomic status and have less social support then men, however, these variables were not available for our study.
Table 4.
Demographics and Baseline Characteristics of Patients With and Without Follow-up.
| CPAP follow-up | No CPAP follow-up | P-value | |
|---|---|---|---|
| Patient Number | 323 | 172 | |
| Male, % | 48.6% | 61% | 0.009 |
| African American, % | 74.5% | 81.3% | 0.478 |
| Married, % | 28.5% | 16.7% | 0.008 |
| Age, y | 48.7 (11.1) | 43.5 (12.8) | 0.261 |
| Body Mass Index, kg/m2 | 45.9 (11.2) | 46.7 (10.8) | 0.997 |
| AHI, events/h | 70.0 (43.7) | 72.5 (45.8) | 0.959 |
| No insurance coverage, % | 72.7% | 79.3% | 0.134 |
| Epworth Sleepiness Scale score | 16.1 (5.9) | 15.1 (6.5) | 0.369 |
Data presented as mean±SD unless otherwise stated.
This cohort of patients is at significant risk of having undiagnosed OSA and experiencing related complications due to poor access and limited utilization of health care. We describe a unique program that provides care for uninsured, minority individuals in a manner similar to patients with the best of health insurance. Despite the elimination of diagnosis and treatment obstacles for sleep apnea, treatment adherence was found to be lower than other populations.
A study by Kripke et al. found frequency of disease was much higher among members of minority groups, ages 40–64, based on measurements of oxygen desaturations.24 Given the high prevalence of obesity and OSA-associated comorbidities in minority populations, the ability to diagnose and effectively treat sleep apnea has the potential to significantly improve the health of minority populations. Further study should focus on additional characteristics that may affect adherence such as socioeconomic status, educational level, and social support systems. By identifying these factors, interventions could be developed and implemented to improve adherence to therapy and diminish the disease burden in similar populations. With the epidemic of obesity and increased awareness of OSA, this population should be further studied to decrease future health disparities in the treatment of this disease
Footnotes
Disclosure Statement
This is not an industry supported study. Dr. James Herdegen has received research support from ResMed, Inc and Respironics, Inc. Dr. Min Joo has indicated no financial conflicts of interest.
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