Residual sleepiness in obstructive sleep apnoea: phenotype and related symptoms

Abstract

The characteristics of residual excessive sleepiness (RES), defined by an Epworth score .10 in adequately treated apnoeic patients, are unknown.40 apnoeic patients, with (n520) and without (n520) RES, and 20 healthy controls underwent clinical interviews, cognitive and biological tests, polysomnography, a multiple sleep latency test, and 24-h sleep monitoring.The marked subjective sleepiness in the RES group (mean¡SD score 16.4¡3) contrasted with moderately abnormal objective measures of sleepiness (90% of patients with RES had daytime sleep latencies .8 min). Compared with patients without RES, the patients with RES had more fatigue, lower stage N3 percentages, more periodic leg movements (without arousals), lower mean sleep latencies and longer daytime sleep periods. Most neuropsychological dimensions (morning headaches, memory complaints, spatial memory, inattention, apathy, depression, anxiety and lack of self-confidence) were not different between patients with and without RES, but gradually altered from controls to apnoeic patients without and then with RES.RES in apnoeic patients differs markedly from sleepiness in central hypersomnia. The association between RES, periodic leg movements, apathy and depressive mood parallels the post-hypoxic lesions in noradrenaline, dopamine and serotonin systems in animals exposed to intermittent hypoxia.

Why excessive sleepiness may persist in OSA patients receiving adequate CPAP treatment

“…We read with interest the paper by VERNET et al [1], which describes the characteristics of residual excessive sleepiness (RES) in obstructive sleep apnoea (OSA) patients treated with continuous positive airway pressure (CPAP). The authors studied two groups of OSA patients, with and without RES.…”

“…Moreover, CPAP treatment does not reduce the high Epworth Sleepiness Score of OS patients [4]. Since arterial carbon dioxide tension was not measured, OHS or OS cannot be excluded in the obese OSA patients with RES studied by VERNET et al [1]. Therefore, RES could be in part explained by the ineffectiveness of CPAP to reduce hypercapnia in OHS or OS patients.…”

“…Thus, cardiovascular autonomic alterations during sleep may be associated with excessive daytime sleepiness, probably because of brainstem dysfunctions involving both alertness and cardiovascular control. Standard polysomnographic studies (like those conducted by VERNET et al [1]) cannot detect these alterations. If such alterations were found, they would support the speculation of VERNET et al [1] that intermittent hypoxia causes a post-hypoxic injury determining ''central hypersomnia''.…”

“…Standard polysomnographic studies (like those conducted by VERNET et al [1]) cannot detect these alterations. If such alterations were found, they would support the speculation of VERNET et al [1] that intermittent hypoxia causes a post-hypoxic injury determining ''central hypersomnia''. In fact, this is what can be expected if the injury affects specific neuronal groups in the brainstem.…”

“…Castiglioni and co-workers suggest that residual excessive sleepiness (RES) in patients with obstructive sleep apnoea (OSA) who are adequately treated with nasal positive airway pressure may be caused by a concomitant, untreated hypercapnia (if OSA overlaps with obesity hypoventilation syndrome or with chronic obstructive pulmonary disease) or by persistent autonomic subcortical arousals. We examined with interest both hypotheses, but neither fits our series [1]. Concomitant chronic obstructive pulmonary disease was a criterion for exclusion (as was any medical disease that could cause sleepiness per se), after reviewing the clinical history and respiratory function tests.…”