Underdiagnosis of OSA in the Cardiology Outpatient Setting
Underdiagnosis of OSA in the Cardiology Outpatient Setting
This study was approved by our local Ethics Committee (# 3795/12/051), and all participants gave a written informed consent. During 6 months of recruitment, we targeted to evaluate 500 consecutive outpatients undergoing regular treatment at the Heart Institute (InCor), University of São Paulo Medical School. These patients came from five subspecialties of the Heart Institute (100 patients each): (1) hypertension, (2) coronary, (3) arrhythmia, (4) heart failure (HF) and (5) valvular heart disease. We excluded patients who refused to participate as well as patients with significant cognitive impairment. All participants underwent clinical evaluation by the same investigator (LEC), which included demographic data, anthropometric measurements, questionnaires for assessing the risk of OSA (Berlin Questionnaire) and excessive daytime sleepiness (Epworth Sleepiness Scale). Briefly, the Berlin Questionnaire evaluates the risk of OSA on the basis of the responses in three symptom categories. In category 1, high risk is defined as persistent symptoms (>3–4 times/week) for ≥2 questions about snoring. In category 2, high risk is defined as persistent (>3–4 times/week) daytime tiredness or fatigue. In category 3, high risk is defined as a history of high blood pressure or body mass index (BMI) >30 kg/m. High risk of OSA is defined when ≥2 symptom categories are positive. In the Epworth Sleepiness Scale, we determined the general level of daytime sleepiness by having patients rate the likelihood of dozing during eight different daytime situations. The scale ranges from 0 to 24, and scores >10 were considered associated with excessive daytime sleepiness.
In addition, we evaluated the awareness of OSA in high-risk individuals as well as specific treatment in those with a high risk for OSA. In addition, we randomly selected 50 patients (10 patients from each specialty) to undergo portable sleep monitoring (ApneaLink Plus, ResMed, ResMed, Sydney, Australia). This is a simple, automated two-channel (oximetry and nasal pressure) screening device. ApneaLink Plus is a validated tool for diagnosing OSA that is used in patients with cardiovascular disease in the ongoing SAVE trial. In our study, hypopnoea was defined as 50% airflow lasting ≥10 s, associated with an oxygen desaturation of >3%. Apnoea was defined as a drop in the peak signal excursion of airflow by ≥90% of pre-event baseline lasting ≥10 s. OSA was defined by an apnoea–hypopnoea index ≥15 events/h of sleep.
The data were analysed using the Statistical Package for Social Sciences, V.10.0, statistical software (SPSS, Chicago, Illinois, USA). The sample size calculation was estimated based on the fact that these five subspecialties together are following around 30 000 outpatients in our Institute. Our primary goal was to evaluate the overall underdiagnosis of OSA in the cardiology setting (and not by specific diseases). We estimated that 50% of them presented a high risk for OSA. Our sample size of 500 patients allowed us to have a 95% CI of 45.7% to 54.3%.
Quantitative variables are expressed as the mean±SD. A comparison of continuous variables between patients with and without OSA was performed using the Student's t test or Wilcoxon test, as appropriate. Categorical variables were expressed as frequency distribution and were compared using the χ test or Fisher's exact test. Frequency comparisons between the five different cardiology subspecialties were analysed by logistic regression analysis. For all these procedures, a significance level of 5% was adopted.
Methods
This study was approved by our local Ethics Committee (# 3795/12/051), and all participants gave a written informed consent. During 6 months of recruitment, we targeted to evaluate 500 consecutive outpatients undergoing regular treatment at the Heart Institute (InCor), University of São Paulo Medical School. These patients came from five subspecialties of the Heart Institute (100 patients each): (1) hypertension, (2) coronary, (3) arrhythmia, (4) heart failure (HF) and (5) valvular heart disease. We excluded patients who refused to participate as well as patients with significant cognitive impairment. All participants underwent clinical evaluation by the same investigator (LEC), which included demographic data, anthropometric measurements, questionnaires for assessing the risk of OSA (Berlin Questionnaire) and excessive daytime sleepiness (Epworth Sleepiness Scale). Briefly, the Berlin Questionnaire evaluates the risk of OSA on the basis of the responses in three symptom categories. In category 1, high risk is defined as persistent symptoms (>3–4 times/week) for ≥2 questions about snoring. In category 2, high risk is defined as persistent (>3–4 times/week) daytime tiredness or fatigue. In category 3, high risk is defined as a history of high blood pressure or body mass index (BMI) >30 kg/m. High risk of OSA is defined when ≥2 symptom categories are positive. In the Epworth Sleepiness Scale, we determined the general level of daytime sleepiness by having patients rate the likelihood of dozing during eight different daytime situations. The scale ranges from 0 to 24, and scores >10 were considered associated with excessive daytime sleepiness.
In addition, we evaluated the awareness of OSA in high-risk individuals as well as specific treatment in those with a high risk for OSA. In addition, we randomly selected 50 patients (10 patients from each specialty) to undergo portable sleep monitoring (ApneaLink Plus, ResMed, ResMed, Sydney, Australia). This is a simple, automated two-channel (oximetry and nasal pressure) screening device. ApneaLink Plus is a validated tool for diagnosing OSA that is used in patients with cardiovascular disease in the ongoing SAVE trial. In our study, hypopnoea was defined as 50% airflow lasting ≥10 s, associated with an oxygen desaturation of >3%. Apnoea was defined as a drop in the peak signal excursion of airflow by ≥90% of pre-event baseline lasting ≥10 s. OSA was defined by an apnoea–hypopnoea index ≥15 events/h of sleep.
Statistical Analysis
The data were analysed using the Statistical Package for Social Sciences, V.10.0, statistical software (SPSS, Chicago, Illinois, USA). The sample size calculation was estimated based on the fact that these five subspecialties together are following around 30 000 outpatients in our Institute. Our primary goal was to evaluate the overall underdiagnosis of OSA in the cardiology setting (and not by specific diseases). We estimated that 50% of them presented a high risk for OSA. Our sample size of 500 patients allowed us to have a 95% CI of 45.7% to 54.3%.
Quantitative variables are expressed as the mean±SD. A comparison of continuous variables between patients with and without OSA was performed using the Student's t test or Wilcoxon test, as appropriate. Categorical variables were expressed as frequency distribution and were compared using the χ test or Fisher's exact test. Frequency comparisons between the five different cardiology subspecialties were analysed by logistic regression analysis. For all these procedures, a significance level of 5% was adopted.
