Gender differences on polysomnographic findings in Greek subjects with obstructive sleep apnea syndrome.

BACKGROUND AND PURPOSE: Studies from North American clinics have reported that females with obstructive sleep apnea syndrome (OSAS) are about the same age as males but are heavier, have less severe apnea and make up a much smaller proportion of cases. We examined polysomnographic differences between Greek men and women with OSAS in order to study the influence of gender on clinical presentation and laboratory findings. PATIENTS AND METHODS: This retrospective study included a cohort of 1,010 Greek patients (844 males, 166 females) diagnosed with OSAS by overnight polysomnography (PSG), who were referred to the Sleep Disorders Center of Evangelismos Hospital, Athens Medical School, University of Athens. All patients were studied over a period of three consecutive years, during which time clinical and polysomnography (PSG) findings were compared. RESULTS: Body mass index (BMI) was similar in men and women with OSAS (BMI=31.6+/-5.5kg/m(2) in men versus BMI=32.5+/-8.1 (SD) kg/m(2) in women). Female patients were significantly older than male patients (56.9+/-10.6 versus 50.6+/-11.7 year, P=0.001). The mean apnea-hypopnea index (AHI) during total sleep time was higher in men than in women (42.4+/-28.2 versus 33.2+/-27.7 events/h, P<0.001). The AHI in non-rapid eye movement (NREM) sleep was higher in men than in women (42.9+/-28.9 versus 32.6+/-28.7 events/h, P<0.001), but in rapid eye movement (REM) sleep AHI was similar in men and women (36.0+/-23.3 versus 34.9+/-25.4 events/h). Forty percent of men had AHI-REM sleep >AHI-NREM compared to 62% of women, and the difference between REM and NREM-AHI was significantly less in men than in women (14.21+/-11.18 versus 19.76+/-13.43 events/h, P<0.001)). Several aspects of sleep were worse in women versus men: sleep efficiency index was lower (79.4+/-16.1% versus 85.1+/-12.5%, P<0.001); sleep onset latency (27.7+/-27.7 versus 17.9+/-18.1min, P<0.001), and REM onset latency (161.5+/-76.2 versus 145.7+/-71.4min, P<0.018) were longer; wake time after sleep onset (WASO) was also greater in women (42.6+/-46.5 versus 30.7+/-34.9min, P<0.003). CONCLUSIONS: In Greek subjects with OSAS, there was no difference in BMI, and female patients were significantly older than male patients. OSAS was diagnosed in men five times more often than in women. AHI was greater in men than in women, but women are more likely than men to have a higher AHI in REM than NREM. Sleep quality is worse in female than in male patients.

Review article: sleep and its relationship to gastro-oesophageal reflux.

Gastro-oesophageal reflux disease (GERD) is among the most common gastrointestinal conditions in the USA. For most symptomatic patients, reflux events occur during both daytime and night-time hours. Whereas daytime reflux events tend to be frequent but brief, reflux events that occur during sleep are comparatively less frequent but significantly longer. Longer oesophageal acid-clearance and acid-mucosal contact times during sleep are at least partly due to several physiological changes associated with sleep, including dramatic declines in saliva production and frequency of swallowing, decreased conscious perception of heartburn and consequent arousal and clearance behaviours, and slower gastric emptying. Obstructive sleep apnea syndrome and obesity seem to predispose some patients to nocturnal GERD, and the presence of either of these conditions may help to identify patients with symptoms consistent with GERD. Recognition and treatment of night-time GERD are important because it can be associated with decreased quality of life (including sleep disruption) and increased risk of serious oesophageal and respiratory complications.

Cardiovascular medication use in patients with undiagnosed obstructive sleep apnoea.

BACKGROUND: A study was undertaken in patients with undiagnosed sleep apnoea/hypopnoea syndrome (OSAS) to document the use of prescribed medications, especially those used in cardiovascular diseases, in the year before the OSAS diagnosis was confirmed. METHODS: A total of 549 patients with OSAS (401 men of mean age 47.2 years, mean body mass index (BMI) 35.5 kg/m(2), mean apnoea/hypopnoea index (AHI) 47.2 and148 women of mean age 50.2 years, BMI 39.6 kg/m(2), AHI 32.6) were each matched to one general population control by age, sex, geographical location, and family physician. Medication use was evaluated for patients and controls using a database containing information about all prescriptions completed in the province of Manitoba, Canada. RESULTS: In the year before OSAS was diagnosed, prescribed medication costs were $155.91 (Canadian dollars) (95% CI $91.34 to $220.49) greater for cases than for controls. Cases were dispensed 3.3 (95% CI 1.5 to 5.2) more prescriptions, were on 1.2 (95% CI 0.8 to 1.6) more medications, and were supplied with 157.4 (95% CI 95.9 to 218.8) more daily doses of medication. The odds ratio of OSAS cases being on a prescribed medication was 1.88 relative to controls (95% CI 1.38 to 2.54, p<0.0001). In the same year 36.6% of cases and 19.7% of controls were using medications for cardiovascular disease (OR 2.82, 95% CI 2.05 to 3.89, p<0.0001), consuming 79.4 (95% CI 48.9 to 109.8) more daily doses of medication, having been dispensed 1.7 (95% CI 1.0 to 2.4) more prescriptions, and at a $75.26 (95% CI $44.03 to $106.50) greater cost. The odds ratio of patients with OSAS being on medications indicated for the treatment of systemic hypertension was 2.71 (95% CI 1.96 to 3.77) relative to controls; however, such medications might also be prescribed for other indications such as angina pectoris and congestive heart failure, and for the secondary prevention of myocardial infarction. The use of medications indicated for the treatment of systemic hypertension was predicted significantly by age (odds ratio (OR) 1.10 per year), BMI (OR 1.05 per unit), and AHI (OR 1.01 per unit). CONCLUSIONS: In the year before OSAS was diagnosed, patients with OSAS were heavy users of medications, particularly those used to treat cardiovascular diseases.

The use of health-care resources in obesity-hypoventilation syndrome.

OBJECTIVE: To document health-care utilization (ie, physician claims and hospitalizations) in patients with obesity-hypoventilation syndrome (OHS), for 5 years prior to the diagnosis and for 2 years after the diagnosis and initiation of treatment. DESIGN: Retrospective observational cohort study. SETTING: University-based sleep disorders center in Manitoba, Canada. PATIENTS AND CONTROL SUBJECTS: Twenty OHS patients (mean [+/- SD] age, 52.7 +/- 9.5 years; body mass index [BMI], 47.3 +/- 11.0 kg/m(2); PaCO(2), 59.7 +/- 13.8 mm Hg; PaO(2), 51.6 +/- 12.4 mm Hg) were matched to two sets of control subjects. First, each case was matched to 15 general population control subjects (GPCs) by age, gender, and geographic location, and, second, each case was matched to a single obese control subject (OBC) who was matched using the same criteria as for the GPCs, plus the measurement of BMI. MEASUREMENTS AND RESULTS: In the 5 years before diagnosis, the 20 OHS patients had (mean +/- SE) 11.2 +/- 1.8 physician visits per patient per year vs 5.7 +/- 0.8 (p < 0.01) visits for OBCs and 4.5 +/- 0.4 (p < 0.001) visits for GPCs. OHS patients generated higher fees, $623 +/- 96 per patient per year for the 5 years prior to diagnosis compared to $252 +/- 34 (p < 0.001) for OBCs and $236 +/- 25 (p < 0.001) for GPCs. OHS patients were much more likely to be hospitalized than were subjects in either control group in the 5 years prior to diagnosis (odds ratio [OR] vs GPCs, 8.6) (95% confidence interval [CI], 5.9 to 12.7); OR vs OBCs, 4.9 (95% CI, 2.3 to 10.1). In the 2 years after diagnosis and the initiation of treatment (usually continuous positive airway pressure or bilevel positive airway pressure), there was a significant linear reduction in physician fees. In the 2 years after the initiation of treatment, there was a 68.4% decrease in days hospitalized per year (5 years before treatment, 7.9 days per patient per year; after 2 years of treatment, 2.5 days per patient per year [p = 0.01]). CONCLUSIONS: OHS patients are heavy users of health care for several years prior to evaluation and treatment of their sleep breathing disorder; there is a substantial reduction in days hospitalized once the diagnosis is made and treatment is instituted.

Sleep complaints and restless legs syndrome in adult type 2 diabetics.

OBJECTIVE: To determine the prevalence and characteristics of sleep complaints and restless legs syndrome (RLS) in type 2 adult diabetics. To test the hypothesis that sleep complaints are more common among adult diabetics. BACKGROUND: Restless legs syndrome is a common disorder and is a cause of insomnia and daytime somnolence. An association between RLS and diabetes mellitus has been hypothesized but has not been established. METHODS: Consecutive type 2 diabetic patients and controls were subjected to sleep questionnaires, examinations for sensory neuropathy, and laboratory investigations. RESULTS: Diabetics had higher rates of insomnia (50 vs. 31%, P=0.04) and used more hypnotics (25.9 vs. 6.0%, P=0.02) than controls. The proportion of diabetics with elevated Epworth Sleepiness Scores (> or =12) was higher than controls (15.5 vs.2.1%, P=0.02). The prevalence of RLS among diabetics was not significantly different than in controls (24.1 vs. 12.5%, P=0.1). The prevalence of sensory polyneuropathy was similar in diabetics with and without RLS. Age, BMI, duration and level of diabetes control, hemoglobin, ferritin and creatinine levels did not predict the presence of RLS in diabetics. CONCLUSIONS: Adult type 2 diabetics have higher rates of insomnia, excessive somnolence and hypnotic use than controls. There is no evidence that RLS is significantly more common in adult diabetics.

Radiofrequency tissue reduction of the palate in patients with moderate sleep-disordered breathing.

OBJECTIVE: Radiofrequency volumetric reduction of the palate has been advocated as a treatment for mild sleep-disordered breathing (SDB). Our study examines the efficacy of this procedure on patients with mostly moderate SDB. DESIGN: Prospective, nonrandomized, consecutive series. SETTING: St. Boniface Hospital, Sleep Disorders Centre, University of Manitoba, Winnipeg. METHOD: Twelve patients with polysomnographically proven moderate SDB were given a total of 2400 to 3600 joules of radiofrequency energy to their soft palate over two to three treatments. Follow-up examined the effect of treatment on subjective and objective parameters including the Epworth Sleepiness Scale, loudness of snoring, Apnea-Hypopnea Index (AHI), and Arousal Index. RESULTS: Two of 12 patients had a good objective response to treatment in that their AHI dropped by more than 50% and to a value of less than 20. However, none of the patients claimed to have a satisfactory subjective response. There was a slight reduction in the mean AHI from 31.2+/-5.1 to 25.3+/-4.2 (p < .05), but no clinically significant difference was found between pre- and post-treatment groups with respect to other sleep parameters. There was no improvement in daytime sleepiness or snoring. CONCLUSIONS: Radiofrequency tissue ablation of redundant soft palate tissues lacks clinical efficacy in patients with moderate SDB.

Diagnosis and management of sleep apnea syndrome.

Sleep apnea is the cessation of breathing during sleep. These episodes result in hypoxemia and sleep disruption; thus the consequences are both cardiorespiratory and neural. Sleep apnea syndrome is defined by a constellation of signs and symptoms, with the main presenting symptom being excessive daytime sleepiness. A diagnosis requires documentation of episodes of abnormal breathing during sleep. This disorder, once thought to be very rare, is so common that it is unlikely that any busy clinician has not encountered a case. Facilities for the evaluation of sleep breathing disorders are now available in most communities. With the introduction of continuous positive airway pressure and other treatments, most patients have complete resolution of their disabling symptoms.

Health care utilization in males with obstructive sleep apnea syndrome two years after diagnosis and treatment.

OBJECTIVE: To document changes in health care utilization (physician claims and hospitalizations) two years after diagnosis and treatment of patients with OSAS. DESIGN: Prospective observational cohort study. SETTING: The study was done in the Canadian Province of Manitoba. OSAS patients were selected from a University-based sleep disorders center. Control subjects were selected from the general population. PATIENTS AND CONTROLS: There were 344 OSAS patients on whom there was utilization data for the period of the study. They were matched to controls from the general population by gender, age, and geographic location. MEASUREMENTS AND RESULTS: The difference in physician claims between the patients and their matched controls two years after diagnosis and treatment ($174+/-32.4 (SE) per year in Canadian dollars) was significantly less than the difference in the year before diagnosis ($260+/-35.7 (SE), p=0.038). Examining the subgroups of patients adhering (PAT) or not adhering (PNAT) to treatment revealed that the changes were only significant in the patients adhering to treatment. Hospital stays for the entire OSAS group decreased from 1.27 days+0.25(SE) per patient per year one year before diagnosis to 0.54+0.13 per patient per year (p=0.01). The changes in the PAT group (1.25+0.28 per patient per year one year before diagnosis to 0.53+0.14 per patient per year (p=0.034) were significant while in the PNAT group they were not. CONCLUSIONS: Adherence to treatment in patients with OSAS results in a significant reduction in physician claims and hospital stays.

Upper airway resistance syndrome: effect of nasal dilation, sleep stage, and sleep position.

BACKGROUND: The upper airway resistance syndrome (UARS) is one of the mild variants of obstructive sleep disordered breathing. Nasal obstruction is proposed as one of the mechanisms that lowers intrapharyngeal pressure and hence increases airway collapsibility. OBJECTIVE: We evaluated the effect of external nasal dilation and sleep position on sleep in UARS. METHOD: A double blind, randomized, controlled study with a crossover design (using therapeutic and placebo dilators) was conducted in 18 consecutive patients with UARS. Each patient had two overnight sleep studies one to two weeks apart. Cardiorespiratory parameters (AHI, percentage of time that SaO2 was more than 2% below awake [desaturation time] and mean overnight heart rate), sleep architecture (sleep stages, sleep efficiency, and arousal index), and body position were determined. RESULTS: Application of the external nasal dilator resulted in a significant increase in the nasal cross-sectional area (p < 0.001). Treatment reduced stage 1 sleep (as a percent of total sleep time) from 8.6 +/- 0.8% to 7.1 +/- 0.7 (SEM), p = 0.034). Desaturation time was significantly lower with treatment (12.2 +/- 2.2% on placebo versus 9.1 +/- 1.3 on treatment, p = 0.04). There were no additional significant effects on the cardiorespiratory parameters, sleep architecture, or MSLT when the entire night was examined. Controlling for interactions of sleep stage and position and treatment we found that treatment reduced desaturation time (p = 0.03) but not AHI or arousal index. AHI was significantly lower in the lateral position compared to the supine (p = 0.0001) and in NREM sleep compared to REM (p = 0.001). Desaturation time was significantly lower on the lateral compared to the supine position (p = 0.002) and in NREM sleep compared to REM (p = 0.006). Arousal index was highly dependent on sleep stage (p = 0.0001): the index was higher in stage 2 compared to slow wave sleep and REM. Sleep position and treatment had no significant effect on arousals. CONCLUSIONS: External nasal dilation reduced stage 1 sleep, an indirect marker of disrupted sleep, and desaturation time. There were no additional effects on sleep architecture or sleep disordered breathing. Both sleep position and sleep stage had a significant effect on sleep disordered breathing in UARS.

Clinical presentations of obstructive sleep apnea syndrome.

Obstructive sleep apnea syndrome (OSAS) is a common but still underrecognized disorder. It affects 2% to 4% of middle-aged adults, a significant proportion of whom are female. The spectrum of clinical presentations of OSAS and their severity is variable, ranging from neurocognitive complaints to cardiorespiratory failure. OSAS has a significant impact on quality of life, cardiovascular morbidity, and mortality. Its major sequelae include daytime somnolence and its consequences (motor vehicle accidents, poor work performance, disrupted social interactions), systemic and pulmonary hypertension, and ischemic heart disease. Treatment of OSAS results in improvement in symptoms, quality of life, and blood pressure control, and may improve mortality. An expansion of our understanding of this condition has resulted in increased awareness of its consequences, but the recognition of OSAS in clinical practice is still delayed. Identification of these patients in clinical practice requires attention to risk factors (history of snoring and witnessed apneas, obesity, increased neck circumference, hypertension, family history) and careful examination of the upper airway. Clinical impression alone, however, has poor (50% to 60%) sensitivity and specificity (63% to 70%) and the diagnosis is usually obtained on polysomnography. Physicians and other health care professionals need to be aware of the progress made in this area and recognize the necessity for prompt evaluation and treatment of these patients.

Decision making in obstructive sleep-disordered breathing: putting It all together

Obstructive sleep-disordered breathing consists of a spectrum ranging from the upper airway resistance syndrome to complete apnea. Although this disorder is relatively common, it is still under-recognized, resulting in a significant increase in morbidity and mortality. This article describes the rationale for treating this disorder. Then, using the best available evidence, develops a systemic approach to the problem, covering recognition, diagnosis, and treatment.

Health care utilization in the 10 years prior to diagnosis in obstructive sleep apnea syndrome patients.

Obstructive sleep apnea syndrome (OSAS) patients may have symptoms for years prior to recognition of their disorder, or they may be treated for the associated comorbidities. We hypothesized that such patients would be heavy consumers of health care resources for several years prior to diagnosis. We therefore compared health service utilization for a 10-year interval prior to diagnosis of 181 OSA patients to those of randomly selected age-, gender-, and geographically matched controls from the general population. OSAS patients used approximately twice as many health care services (as defined by physician claims and overnight stays in hospital) in the 10 years prior to their initial diagnostic evaluation for apnea. Physician claims for the OSA patients totaled $686,365 ($3972 per patient), compared to $356,376 ($1969 per patient) for the controls for the 10-year period examined in this study. Use of health services was significantly higher in 7 of 10 years prior to diagnosis. The OSAS patients also had more overnight hospitalizations: they spent 1118 nights (6.2 per patient) in hospital vs 676 nights (3.7 per patient) for controls in the decade prior to diagnosis. We conclude that by the time patients are finally diagnosed for sleep apnea, they have already been heavy users of health services for several years. It is possible that our findings reflect not OSAS per se, but the presence of some of the risk factors that predispose to OSAS, such as obesity, alcohol usage and perhaps tobacco consumption.

Effect of pergolide on restless legs and leg movements in sleep in uremic patients.

Restless legs syndrome (RLS) and periodic limb movements in sleep (PLMS) are disorders that are common and disturbing to uremic patients. The treatment of these is problematic. Eight patients on chronic hemodialysis and continuous peritoneal dialysis completed a double-blind placebo-controlled crossover study using incremental doses of pergolide up to 0.25 mg at bedtime for treatment of RLS and sleep disruption. Five patients (62.5%) noted subjective improvement in restless legs symptoms and sleep quality. Objective results were improved only slightly by treatment. The percentage of the first hour in bed during which leg movements occurred decreased from 20.5 +/- 6.0 to 11.5 +/- 3.3, p < 0.05. However, findings during sleep were less positive. The following measures were not significant between placebo and treatment: leg movements per hour of sleep [53.7 +/- 22.3 vs 35.8 +/- 11.8 (p = 0.2)]; and percentage of sleep time spent with leg movements [5.5% +/- 3.2 vs 4.4% +/- 1.4 (p = 0.37)]. Patients continued to have very disrupted sleep, and we could not document an objective improvement in sleep architecture. Thus, although pergolide at the dose of 0.25 mg at bedtime provided subjective improvement in symptoms of restless legs and quality of sleep, and objectively decreased leg movements during the first hour in bed, objectively sleep continued to be disrupted. In this small patient group, the response to pergolide was not uniform, and further investigation is required to test effectiveness at higher doses.

Susceptibility of LDL to oxidative stress in obstructive sleep apnea.

Cardiovascular diseases are more common in patients with obstructive sleep apnea (OSA) than in the general population. We hypothesized that severe hypoxemia during sleep in these patients may cause an imbalance between reactive oxygen species and the antioxidant reserve that is important for the detoxification of these molecules. We tested the hypothesis that low-density lipoproteins (LDL) in hypoxic OSA patients may be more susceptible to oxidative stress than LDL of nonhypoxic OSA patients and normal controls. Fifteen OSA patients were included in this study, six with severe hypoxia (hypoxic group) who spent more than 10 minutes during sleep with SaO2 < 85% (mean 96 minutes), and nine OSA patients (nonhypoxic group) who spent less than 10 minutes during sleep with SaO2 < 85% (mean 1.1 minutes). Six healthy nonsmoking males of the same age group were included as a control group. The susceptibility of each individual's LDL to oxidative stress was examined after free-radical challenge in vitro by assessing changes in levels of conjugated dienes. The LDL in OSA patients with severe hypoxia was not more susceptible to oxidative stress compared to the LDL of nonhypoxic OSA patients and normal controls. After 6 hours of exposure to an oxidative agent, the changes in the mean conjugated diene were not different among the three groups (p = 0.75). The time required to reach 50% of maximal absorbance was also not different, p = 0.199. Glutathione peroxidase and catalase activities in red blood cells in the hypoxic and nonhypoxic patient groups were not significantly different. One night of CPAP therapy in each patient group did not significantly change the level of the antioxidant enzymes. Our results did not show any difference in the susceptibility to oxidative stress between hypoxic and nonhypoxic OSA patients and normal controls.

Decision making in obstructive sleep-disordered breathing. Putting it all together.

Obstructive sleep-disordered breathing consists of a spectrum ranging from the upper airway resistance syndrome to complete apnea. Although this disorder is relatively common, it is still under-recognized, resulting in a significant increase in morbidity and mortality. In this article, we describe the rationale for treating this disorder. Then, using the best available evidence, we try to develop a systemic approach to the problem, covering recognition, diagnosis, and treatment.

Obstructive sleep apnea patients use more health care resources ten years prior to diagnosis.

Because Obstructive Sleep Apnea Syndrome (OSAS) patients may be treated for comorbidities prior to OSAS diagnosis, we examined the health care utilization records of 181 OSAS patients and those of matched controls. We compared OSA patient health care utilization for a ten-year interval prior to diagnosis to those of randomized age-, gender-, and geographically-matched controls from the general population. We found that OSAS patients used approximately twice the resources (as defined by physician claims and stays in hospital) in the ten years prior to their diagnosis. Physician claims for cases totaled $686,365 ($3,972 per patient) compared to $356,376 ($1,969 per patient) for the controls for the length of the study. Utilization was significantly higher in 7 of 10 years prior to diagnosis. OSAS patients also had more hospitalizations: they had 1,118 nights (6.2 per patient) in hospital versus 676 nights (3.7 per patient) for controls over the ten-year period. Thus OSA patients are heavy users of health care resources ten years prior to diagnosis.

Randomized, double-blind, placebo-controlled crossover trial of modafinil in the treatment of excessive daytime sleepiness in narcolepsy.

Seventy-five patients meeting international diagnostic criteria for narcolepsy enrolled in a 6-week, three-period, randomized, crossover, placebo-controlled trial. Patients received placebo, modafinil 200 mg, or modafinil 400 mg in divided doses (morning and noon). Evaluations occurred at baseline and at the end of each 2-week period. Compared with placebo, modafinil 200 and 400 mg significantly increased the mean sleep latency on the Maintenance of Wakefulness Test by 40% and 54%, with no significant difference between the two doses. Modafinil, 200 and 400 mg, also reduced the combined number of daytime sleep episodes and periods of severe sleepiness noted in sleep logs. The likelihood of falling asleep as measured by the Epworth Sleepiness Scale was equally reduced by both modafinil dose levels. There were no effects on nocturnal sleep initiation, maintenance, or architecture, nor were there any effects on sleep apnea or periodic leg movements. Neither dose interfered with the patients' ability to nap voluntarily during the day nor with their quantity or quality of nocturnal sleep. Modafinil produced no changes in blood pressure or heart rate in either normotensive or hypertensive patients. The only significant adverse effects were seen at the 400-mg dose, which was associated with more nausea and more nervousness than either placebo or the 200-mg dose. As little as a 200-mg daily dose of modafinil is therefore an effective and well-tolerated treatment of excessive daytime somnolence in narcoleptic persons.

Using self-reported questionnaire data to prioritize OSA patients for polysomnography.

Many laboratories have large numbers of patients with suspected obstructive sleep apnea (OSA) waiting to be tested. We assessed the use of simple clinical data to detect those patients with an apnea index <20 (low AI) who could be studied less emergently. Using questionnaires completed by patients prior to evaluation, we collected data on 354 consecutive patients (281 males, 73 females; mean age 48.6 years) referred for OSA and assessed with polysomnography (PSG). The questionnaires included the Epworth sleepiness scale (ESS), height, weight, age, and a history of observed apnea. Analysis of receiver operating characteristics curves revealed that both body mass index (BMI) [area under curve = 0.7258, standard error (SE) = 0.03, p < 0.01] and ESS (area under curve = 0.5581, SE = 0.03, p = 0.03) were significantly better than chance alone in detecting people with AI < 20. ESS < or =12 was found in 37.9% of the subjects but 39.6% of those expected to have a low AI using ESS had an AI > or =20. A BMI < or =28 was found in 24.9% of the subjects; 14.8% of those expected to have a low AI using BMI had an AI > or =20. Combining these variables improved accuracy but resulted in smaller groups; a cut-off of ESS < or =12 and BMI < or =28 resulted in a group of 33 (9.3% of subjects), only two (6%) of whom were falsely called low AI. Adding to this the fact that apnea had not been observed resulted in a group of nine patients (2.5% of subjects), none of whom had an AI > or =20. Thus there is a tradeoff; the more variables used, the greater the accuracy but the smaller the percent of cases selected to have low AI. However, in laboratories with hundreds of patients waiting to be tested, any procedure better than chance to help prioritize patients seems worthwhile.