SUMMARYThe aim of this study was to identify factors other than objective sleep tendency associated with scores on the Epworth Sleepiness Scale (ESS). There were 225 subjects, of whom 40% had obstructive sleep apnoea (OSA), 16% had simple snoring, and 4.9% had snoring with sleep disruption (upper airway resistance syndrome); 9.3% had narcolepsy and 7.5% had hypersomnolence without REM sleep abnormalities; 12% had chronic fatigue syndrome; 7.5% had periodic limb movement disorder and 3% had diurnal rhythm disorders. ESS, the results of overnight polysomnography and multiple sleep latency test (MSLT) and SCL-90 as a measure of psychological symptoms were recorded. The ESS score and the mean sleep latency (MSL) were correlated (Spearman =−0.30, P<0.0001). The MSL was correlated with total sleep time (TST) and with sleep efficiency but not with apnoea/hypopnoea index. There was no association between the MSL and any aspect of SCL-90 scores, except a borderline significant association with the somatisation subscale. The ESS was correlated with TST but not with sleep efficiency or apnoea/hypopnoea index. The ESS was correlated with all subscales of the SCL-90 except psychoticism. An ESS[10 had poor sensitivity and specificity as a predictor of MSL <10 min or MSL <5 min. We conclude that the MSLT and the ESS are not interchangeable. The ESS was influenced by psychological factors by which the MSL was not affected. The ESS cannot be used to demonstrate or exclude sleepiness as it is measured by MSLT.

, 793 patients suspected of having sleep-disordered breathing had unattended overnight oximetry in their homes followed by laboratory polysomnography. From the oximetry data we extracted cumulative percentage time at S a O 2 < 90% (CT 90 ) and a saturation variability index ( Index, the sum of the differences between successive readings divided by the number of readings -1). CT 90 was weakly correlated with polysomnographic apnea/hypopnea index (AHI), (Spearman =0.36, P< 0.0001) and with Index ( =0.71, P< 0.0001). Index was more closely correlated with AHI ( =0.59, P< 0.0001). In a multivariate model, onlyIndex was significantly related to AHI, the relationship being AHI=18.8 Index +7.7. The 95% CI for the coefficient were 16.2, 21.4, and for the constant were 5.8, 9.7. The sensitivity of a Index cut-off of 0.4 for the detection of AHI[15 was 88%, for detection of AHI[20 was 90% and for the detection of AHI[25 was 91%. The specificity of Index [0.4 for AHI[15 was 40%. In 113 further patients, oximetry was performed simultaneously with laboratory polysomnography. Under these circumstances Index was more closely correlated with AHI ( =0.74, P< 0.0001), as was CT 90 ( =0.58, P< 0.0001). Sensitivity of Index [0.4 for detection of AHI[15 was not improved at 88%, but specificity was better at 70%. We concluded that oximetry using a saturation variability index is sensitive but nonspecific for the detection of obstructive sleep apnea, and that few false negative but a significant proportion of false positive results arise from night-to-night variability. oximetry, apnea/hypopnea index, sleep disorder breathing

In order to determine whether the clinical features of obstructive sleep apnoea (OSA) are the same in men and women we reviewed the records of 22 women with OSA. The women were matched with 44 men of similar age (+/- 5 years) and frequency of respiratory events (less than or equal to 15/hr, 16-40/hr, 41-70/hr and greater than 70/hr). The degree of daytime somnolence was similar in men and women. Women are more likely than men to complain of morning fatigue and morning headache, and less likely to report restless sleep or to have been told of apnoea during sleep. Difficulty initiating sleep (DIS) was twice as common in women as in men (p less than 0.05). Most of these differences were also seen when women and men who snored but did not have OSA were compared. Arterial hypertension was less common in women (3/22) than in men (18/44), (p less than 0.001). More striking than the differences between men and women in the prevalence of single symptoms was the existence of a subgroup of women (9/22) with no complaint of either apnoea, choking arousals or restless sleep, and normal blood pressure, complaining only of fatigue and morning headache, and in three cases DIS as well. We concluded that OSA may be commoner in women than previous reports suggest, and that the clinical features may be misleading in women.

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