Hormone treatment gives no benefit against cognitive changes caused by acute sleep deprivation in postmenopausal women

Overnight Heart Rate Variability During Sleep Disturbance In Peri- And Postmenopausal Women

OBJECTIVES

Disturbed sleep, common during the climacteric, is associated with increased sympathetic activity, a cardiovascular risk factor. We evaluated sleep disturbance effect on autonomic nervous function in climacteric women.

METHODS

Seventeen perimenopausal and 18 postmenopausal women underwent a sleep study protocol: an adaptation night, a reference night, and a sleep disturbance night, with a hand loosely tied to the bed to allow blood sampling. This procedure was repeated after six months of menopausal hormone therapy (MHT) or placebo. Sleep disturbance and MHT effects on overnight heart rate variability (HRV) were analyzed.

RESULTS

At baseline, sleep disturbance increased vagal HRV in postmenopausal women, but no changes were seen in perimenopausal women. At six months, sleep disturbance increased total HRV power in the perimenopausal placebo group, and increased nonlinear vagal HRV in the postmenopausal placebo group, but no other changes were seen. MHT did not have any effects on HRV, neither at perimenopause nor at postmenopause.

CONCLUSIONS

External sleep disturbance had only minor effects on HRV across menopause. MHT had no detectable HRV effects.

Cortical gradients of functional connectivity are robust to state-dependent changes following sleep deprivation

Sleep deprivation leads to significant impairments in cognitive performance and changes to the interactions between large scale cortical networks, yet the hierarchical organization of cortical activity across states is still being explored. We used functional magnetic resonance imaging to assess activations and connectivity during cognitive tasks in 20 healthy young adults, during three states: (i) following a normal night of sleep, (ii) following 24hr of total sleep deprivation, and (iii) after a morning recovery nap. Situating cortical activity during cognitive tasks along hierarchical organizing gradients based upon similarity of functional connectivity patterns, we found that regional variations in task-activations were captured by an axis differentiating areas involved in executive control from default mode regions and paralimbic cortex. After global signal regression, the range of functional differentiation along this axis at baseline was significantly related to decline in working memory performance (2-back task) following sleep deprivation, as well as the extent of recovery in performance following a nap. The relative positions of cortical regions within gradients did not significantly change across states, except for a lesser differentiation of the visual system and increased coupling of the posterior cingulate cortex with executive control areas after sleep deprivation. This was despite a widespread increase in the magnitude of functional connectivity across the cortex following sleep deprivation. Cortical gradients of functional differentiation thus appear relatively insensitive to state-dependent changes following sleep deprivation and recovery, suggesting that there are no large-scale changes in cortical functional organization across vigilance states. Certain features of particular gradient axes may be informative for the extent of decline in performance on more complex tasks following sleep deprivation, and could be beneficial over traditional voxel- or parcel-based approaches in identifying realtionships between state-dependent brain activity and behavior.

Sex differences in sleep and sleep loss-induced cognitive deficits: The influence of gonadal hormones

Males and females can respond differentially to the same environmental stimuli and experimental conditions. Chronic sleep loss is a frequent and growing problem in many modern societies and has a broad variety of negative outcomes for health and well-being. While much has been done to explore the deleterious effects of sleep deprivation (SD) on cognition in both human and animal studies over the last few decades, very little attention has been paid to the part played by sex differences and gonadal steroids in respect of changes in cognitive functions caused by sleep loss. The effects of gonadal hormones on sleep regulation and cognitive performances are well established. Reduced gonadal function in menopausal women and elderly men is associated with sleep disturbances and cognitive decline as well as dementia, which suggests that sex steroids play a key role in modulating these conditions. Finding out whether there are sex differences in respect of the effect of insufficient sleep on cognition, and how neuroendocrine mediators influence cognitive impairment induced by SD could provide valuable insights into the best therapies for each sex. In this review, we aim to highlight the involvement of sex differences and gonadal hormone status on the severity of cognitive deficits induced by sleep deficiency in both human and animal studies.

Learning and memory are impaired in the object recognition task during metestrus/diestrus and after sleep deprivation

Females are an under-represented research model and the mechanisms through which sleep loss impairs cognition are not clear. Since levels of reproductive hormones and the estrous cycle are sensitive to sleep loss and necessary for learning and memory, we hypothesized that sleep deprivation impacts learning and memory in female mice by interfering with the estrous cycle. We used the object recognition task to assess learning and memory in female mice during separate phases of the estrous cycle and after sleep loss. Mice in metestrus/diestrus attended to sample objects less than mice in proestrus/estrus during object acquisition, the first phase of the object recognition task. Subsequently, during the recognition phase of the task, only mice in proestrus/estrus displayed a preference for the novel object. Sleep deprivation for 12h immediately before the object recognition task reduced time attending to sample objects and novel object preference for mice in proestrus/estrus, without changing length of the estrous cycle. These results show that sleep deprived mice in proestrus/estrus had learning deficits and memory impairments, like mice in metestrus/diestrus. Since sleep deprivation did not disrupt the estrous cycle, however, results did not support the hypothesis. Cognitive impairments due to acute sleep loss were not due to alterations to the estrous cycle.

Ovarian hormones, sleep and cognition across the adult female lifespan: An integrated perspective

Loss of ovarian function in women is associated with sleep disturbances and cognitive decline, which suggest a key role for estrogens and/or progestins in modulating these symptoms. The effects of ovarian hormones on sleep and cognitive processes have been studied in separate research fields that seldom intersect. However, sleep has a considerable impact on cognitive function. Given the tight connections between sleep and cognition, ovarian hormones may influence selective aspects of cognition indirectly, via the modulation of sleep. In support of this hypothesis, a growing body of evidence indicates that the development of sleep disorders following menopause contributes to accelerated cognitive decline and dementia in older women. This paper draws from both the animal and human literature to present an integrated view of the effects of ovarian hormones on sleep and cognition across the adult female lifespan.

Effect of withdrawal from long-term use of temazepam, zopiclone or zolpidem as hypnotic agents on cognition in older adults

PURPOSE

The aim of this study was to assess the effect of withdrawal from the long-term use of temazepam, zopiclone or zolpidem as hypnotics drugs (here referred to as BZD) on cognitive performance.

METHODS

Ninety-two adults (age ≥55 years) with primary insomnia and who were long-term daily users of BZD volunteered to participate in a 1-month medically supported withdrawal attempt from BZD use, with a subsequent 5-month follow-up. Withdrawal was based on plasma BZD measurements at baseline, at 1 month and during subsequent regular clinical appointments. Attention and psychomotor performance were measured using the CogniSpeed® at baseline and at 1, 2 and 6 months. Reaction times were determined in the Simple Reaction Time (SRT), Two-Choice Reaction Time (2-CRT) and Vigilance tests, and errors were measured by the 2-CRT and Vigilance tests. The cognition data of the withdrawal group were also compared with a cohort of BZD non-users.

RESULTS

Eighty-nine (97 %) participants (59 women, 30 men) were followed-up for a maximum of 6 months. During the follow-up period, changes in reaction times and errors did not differ between short-term withdrawers (no residual BZD at 1 month; N = 69), non-withdrawers (residual BZD at 1 month; N = 20) or long-term withdrawers (N = 34). Compared to the reaction times of the BZD-free cohort, those of BZD users were slower at baseline. The reaction times of BZD withdrawers based on the results of the SRT or 2-CRT tests during follow-up did not reach those of the BZD-free cohort, but there was no difference between these groups in the Vigilance test.

CONCLUSIONS

Long-term use of BDZ as hypnotic drugs by older adults is related to prolonged impairment of attentional and psychomotor cognitive functioning that persists for at least 6 months after withdrawal.

Reduced slow-wave rebound during daytime recovery sleep in middle-aged subjects

Cortical synchronization during NREM sleep, characterized by electroencephalographic slow waves (SW <4Hz and >75 µV), is strongly related to the number of hours of wakefulness prior to sleep and to the quality of the waking experience. Whether a similar increase in wakefulness length leads to a comparable enhancement in NREM sleep cortical synchronization in young and older subjects is still a matter of debate in the literature. Here we evaluated the impact of 25-hours of wakefulness on SW during a daytime recovery sleep episode in 29 young (27y ±5), and 34 middle-aged (51y ±5) subjects. We also assessed whether age-related changes in NREM sleep cortical synchronization predicts the ability to maintain sleep during daytime recovery sleep. Compared to baseline sleep, sleep efficiency was lower during daytime recovery sleep in both age-groups but the effect was more prominent in the middle-aged than in the young subjects. In both age groups, SW density, amplitude, and slope increased whereas SW positive and negative phase duration decreased during daytime recovery sleep compared to baseline sleep, particularly in anterior brain areas. Importantly, compared to young subjects, middle-aged participants showed lower SW density rebound and SW positive phase duration enhancement after sleep deprivation during daytime recovery sleep. Furthermore, middle-aged subjects showed lower SW amplitude and slope enhancements after sleep deprivation than young subjects in frontal and prefrontal derivations only. None of the SW characteristics at baseline were associated with daytime recovery sleep efficiency. Our results support the notion that anterior brain areas elicit and may necessitate more intense recovery and that aging reduces enhancement of cortical synchronization after sleep loss, particularly in these areas. Age-related changes in the quality of wake experience may underlie age-related reduction in markers of cortical synchronization enhancement after sustained wakefulness.

Measurement of cognition in studies of sleep deprivation

Controlled laboratory studies of the effects of sleep deprivation on cognition have the potential to further our understanding of why some complex tasks are more affected by lack of sleep than other tasks. However, apparently simple cognitive tasks reflect multiple cognitive processes at once. Some of the component processes involved in a task may be more affected by sleep deprivation than others. Thus, interpreting measures of overall performance without consideration of the specific task requirements can lead to misleading conclusions. Using examples from studies of attention, working memory and executive functioning, we demonstrate the importance of analysing how different task components contribute to performance and how the nature of the stimulus content can influence outcomes of sleep deprivation studies. Recent developments in cognitive neuropsychology may help sleep researchers conduct more precise tests of fatigue effects on cognition. In turn, studies of sleep and cognition hold promise as a strategy for the development of better general models of how the cognitive system adjusts dynamically to impairments in processing.

Does hormone therapy affect attention and memory in sleep-deprived women?

OBJECTIVES

To evaluate whether hormone therapy (HT) modifies cognitive performance during sleep deprivation in postmenopausal women. Comparison was made with a group of young women.

METHODS

Participants included 26 postmenopausal women (age 58-72 years, 16 HT users, 10 non-users), 11 young women (age 20-26 years). They spent four consecutive nights in the sleep laboratory. Cognitive tests of attention, working memory, and verbal episodic memory were carried out after the baseline night, 25-h sleep deprivation, and recovery night.

RESULTS

Sleep deprivation impaired performance in all groups. It was manifested either as delayed practice effect or deteriorated performance (p < 0.05). In simple reaction time and 10-choice reaction time, non-users and young maintained their performance, whereas HT users suffered a minor impairment (p < 0.01). In other measurements, there was no interaction of group and condition. In 10-choice reaction time and vigilance, postmenopausal women made fewer errors and omissions than the young (p < 0.05). For most tasks, all groups showed improvement after one recovery night.

CONCLUSIONS

HT had a minor adverse effect on cognitive performance during sleep deprivation. Attention and memory deteriorated similarly in postmenopausal and young women, despite the lower initial performance level of postmenopausal women. One night of sleep ensured recovery in most tasks.