Effect of continuous positive airway pressure treatment on short-term memory performance over 24 h of sustained wakefulness in patients with obstructive sleep apnea-hypopnea syndrome.

BACKGROUND: Few studies have examined the impact of continuous positive airway pressure (CPAP) therapy on short-term memory (STM) over sustained wakefulness in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). We have investigated if impaired STM can be reversed by CPAP treatment in a 24-h sustained wakefulness paradigm. METHODS: Our follow-up study was conducted with repeated-memory tasks within 12 OSAHS patients and 10 healthy controls who underwent three 32-h sessions, one before CPAP (T0) and the second (T3) and the third (T6), after 3 and 6 months of treatment, respectively, for OSAHS patients. Each session included one night of sleep followed by 24h of sustained wakefulness, during which both groups performed STM tasks including both digit span (DS) and Sternberg tasks. RESULTS: Untreated OSAHS patients had no deficit in the forward DS task measuring immediate memory but were impaired in STM, especially working memory assessed by the complex Sternberg task and the backward DS. However, only performance in the latter was improved after 6 months of CPAP treatment. CONCLUSIONS: Because the high level of memory scanning required high speed in information processing, persistent impairment on the complex Sternberg task may be attributable to working memory slowing, possibly enhanced by sustained wakefulness.

Short-term memory performances during sustained wakefulness in patients with obstructive sleep apnea-hypopnea syndrome.

Both working and immediate memories were assessed every 4h by specific short-term memory tasks over sustained wakefulness in 12 patients with obstructive sleep apnea and hypopnea syndrome (OSAHS) and 10 healthy controls. Results indicated that OSAHS patients exhibited lower working memory performances than controls on both backward digit span and complex Sternberg tasks. Speed and accuracy on Sternberg tasks were affected by memory load in both groups. However, immediate memory was not impaired in OSAHS patients. Diurnal and nocturnal SaO(2) were correlated with speed and accuracy high-speed memory scanning performance on Sternberg tasks in patients. These results suggest specific working memory deficits associated with OSAHS over sustained wakefulness with a possible deficiency in the central executive responsible for the higher information processing, in addition to a potentially insufficient storage capacity. Among OSAHS patients, working memory ability involved in high-speed memory scanning may be impaired by chronic hypoxemia.

Effects of nocturnal railway noise on sleep fragmentation in young and middle-aged subjects as a function of type of train and sound level.

Due to undisputable effects of noise on sleep structure, especially in terms of sleep fragmentation, the expected development of railway transportation in the next few years might represent a potential risk factor for people living alongside the rail tracks. The aim of this study was to compare the effects of different types of train (freight, automotive, passenger) on arousal from sleep and to determine any differential impact as a function of sound level and age. Twenty young (16 women, 4 men; 25.8 years+/-2.6) and 18 middle-aged (15 women, 3 men; 52.2 years+/-2.5) healthy subjects participated in three whole-night polysomnographic recordings including one control night (35 dBA), and two noisy nights with equivalent noise levels of 40 or 50 dB(A), respectively. Arousal responsiveness increased with sound level. It was the highest in S2 and the lowest in REM sleep. Micro-arousals (3-10 s) occurred at a rate of 25-30%, irrespective of the type of train. Awakenings (>10 s) were produced more frequently by freight train than by automotive and passenger trains. Normal age-related changes in sleep were observed, but they were not aggravated by railway noise, thus questioning whether older persons are less sensitive to noise during sleep. These evidences led to the conclusion that microscopic detection of sleep fragmentation may provide advantageous information on sleep disturbances caused by environmental noises.