Sleep deprivation, cognitive performance, and hormone therapy in postmenopausal women

Evaluation of cognitive and psychomotor faculties in relation to mood-related symptoms under the conditions of sleep deprivation

Introduction

Deprivation of sleep (DS) has been associated with changes in mood and cognitive function, rapidly but transiently improving the severity of depression symptoms. However, it remains unclear whether there are differences in performance between DS responders and non-responders. The relationship between DS, mood, cognitive, and psychomotor function is also poorly understood.

Methods

Participants (n = 77) underwent a baseline assessment of sleep under the control of polysomnography (PSG). Later they were subjected to DS with actigraphy monitoring. Evaluation of mood as well as completing a battery of tests assessing cognitive functions and eye-hand coordination was conducted four times, pre/post PSG and DS. Participants were further divided into respondents (RE, n = 48) and non-respondents (NR, n = 29) depending on alleviation of depression symptoms severity following DS.

Results

All participants exhibited increased response speed to visual triggers after DS compared to baseline (p = 0.024). Psychomotor vigilance test (PVT) results remained intact in the RE, whereas it was increased in the NR (p = 0.008). Exposure time in the eye-hand coordination test improved in both groups, but total error duration was reduced only in RE individuals (p < 0.001, p = 0.009 for RE and NR, respectively). All subjects were more proficient at trail-making test (p ≤ 0.001 for Part 1 and 2 in all, NR, RE). Stroop test also improved regardless of mood changes after DS (p = 0.007, p = 0.008 for Part 1 and 2, respectively); cognitive interference remained at a similar level within groups (p = 0.059, p = 0.057 for NR and RE, respectively). A positive correlation was observed between the difference in PSG morning/DS morning depression severity and vigilance (R = 0.37, p = 0.001, R = 0.33, p = 0.005, for error duration eye-hand coordination test and PVT total average score, respectively).

Conclusion

RE tend to maintain or improve cognitive function after DS, oppositely to NR. Vigilance in particular might be tightly associated with changes in depression symptoms after DS. Future studies should examine the biological basis behind the response to sleep loss.

Sex Hormones, Sleep, and Memory: Interrelationships Across the Adult Female Lifespan

As the population of older adults grows, so will the prevalence of aging-related conditions, including memory impairments and sleep disturbances, both of which are more common among women. Compared to older men, older women are up to twice as likely to experience sleep disturbances and are at a higher risk of cognitive decline and Alzheimer's disease and related dementias (ADRD). These sex differences may be attributed in part to fluctuations in levels of female sex hormones (i.e., estrogen and progesterone) that occur across the adult female lifespan. Though women tend to experience the most significant sleep and memory problems during the peri-menopausal period, changes in memory and sleep have also been observed across the menstrual cycle and during pregnancy. Here, we review current knowledge on the interrelationships among female sex hormones, sleep, and memory across the female lifespan, propose possible mediating and moderating mechanisms linking these variables and describe implications for ADRD risk in later life.

The wake maintenance zone shows task dependent changes in cognitive function following one night without sleep

Study Objectives

The interaction between homeostatic sleep pressure and circadian timing modulates the impact of sleep deprivation on cognition. We aimed to investigate how this interaction affects different cognitive functions.

Methods

Twenty-three healthy volunteers (18 males; mean age = 25.4 ± 5.7 years) underwent 40 hours of sleep deprivation under constant routine conditions. Performance on the Psychomotor Vigilance Test and a cognitive battery assessing vigilant attention, complex attention, recognition memory, and working memory was assessed in the morning (27 hours awake) and evening (37 hours awake) during sleep deprivation and compared to well-rested performance 24 hours earlier. Circadian phase assessments confirmed evening tests occurred in the wake maintenance zone (WMZ).

Results

Increased time awake significantly impacted performance on all measures except recognition memory. Post hoc analyses found performance on all measures was significantly impaired in the morning following 27 hours of sleep deprivation compared to well-rested performance 24 hours earlier. In contrast, complex attention and working memory were preserved in the WMZ after 37 hours awake compared to 24 hours earlier, while vigilant attention and PVT performance were significantly impaired. During sleep deprivation, composite scores of speed and accuracy were both impaired in the morning, while only speed was impaired during the WMZ.

Conclusions

We observed task- and time-dependent effects of sleep deprivation, such that vigilant attention was significantly impaired after both 27 hours and 37 hours awake (compared to when well-rested at the same circadian clock time). In contrast, complex attention and working memory were impaired at 27 hours awake, but preserved in the WMZ despite increased homeostatic sleep pressure (37 hours awake).

Dietary Protein and Amino Acid Intake: Links to the Maintenance of Cognitive Health

With the rapid growth in the aging population, there has been a subsequent increase in the rates of Alzheimer's disease and related dementias (ADRD). To combat these increases in ADRD, scientists and clinicians have begun to place an increased emphasis on preventative methods to ameliorate disease rates, with a primary focus area on dietary intake. Protein/amino acid intake is a burgeoning area of research as it relates to the prevention of ADRD, and consumption is directly related to a number of disease-related risk factors as such low-muscle mass, sleep, stress, depression, and anxiety. As a result, the role that protein/amino acid intake plays in affecting modifiable risk factors for cognitive decline has provided a robust area for scientific exploration; however, this research is still speculative and specific mechanisms have to be proven. The purpose of this review is to describe the current understanding of protein and amino acids and the preventative roles they play with regard to ADRD, while providing future recommendations for this body of research. Additionally, we will discuss the current recommendations for protein intake and how much protein older adults should consume in order to properly manage their long-term risk for cognitive decline.

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.

Effects of total sleep deprivation on divided attention performance

Dividing attention across two tasks performed simultaneously usually results in impaired performance on one or both tasks. Most studies have found no difference in the dual-task cost of dividing attention in rested and sleep-deprived states. We hypothesized that, for a divided attention task that is highly cognitively-demanding, performance would show greater impairment during exposure to sleep deprivation. A group of 30 healthy males aged 21-30 years was exposed to 40 h of continuous wakefulness in a laboratory setting. Every 2 h, subjects completed a divided attention task comprising 3 blocks in which an auditory Go/No-Go task was 1) performed alone (single task); 2) performed simultaneously with a visual Go/No-Go task (dual task); and 3) performed simultaneously with both a visual Go/No-Go task and a visually-guided motor tracking task (triple task). Performance on all tasks showed substantial deterioration during exposure to sleep deprivation. A significant interaction was observed between task load and time since wake on auditory Go/No-Go task performance, with greater impairment in response times and accuracy during extended wakefulness. Our results suggest that the ability to divide attention between multiple tasks is impaired during exposure to sleep deprivation. These findings have potential implications for occupations that require multi-tasking combined with long work hours and exposure to sleep loss.

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.

Free recall of word lists under total sleep deprivation and after recovery sleep

STUDY OBJECTIVES

One task that has been used to assess memory effects of prior total sleep deprivation (TSD) is the immediate free recall of word lists; however, results have been mixed. A possible explanation for this is task impurity, since recall of words from different serial positions reflects use of distinct types of memory (last words: short-term memory; first and intermediate words: episodic memory). Here we studied the effects of 2 nights of TSD on immediate free recall of semantically unrelated word lists considering the serial position curve.

DESIGN

Random allocation to a 2-night TSD protocol followed by one night of recovery sleep or to a control group.

SETTING

Study conducted under continuous behavioral monitoring.

PARTICIPANTS

24 young, healthy male volunteers.

INTERVENTION

2 nights of total sleep deprivation (TSD) and one night of recovery sleep.

MEASUREMENTS AND RESULTS

Participants were shown five 15 unrelated word-lists at baseline, after one and 2 nights of TSD, and after one night of recovery sleep. We also investigated the development of recall strategies (learning) and susceptibility to interference from previous lists. No free recall impairment occurred during TSD, irrespective of serial position. Interference was unchanged. Both groups developed recall strategies, but task learning occurred earlier in controls and was evident in the TSD group only after sleep recovery.

CONCLUSION

Prior TSD spared episodic memory, short-term phonological memory, and interference, allowed the development of recall strategies, but may have decreased the advantage of using these strategies, which returned to normal after recovery sleep.

Burden associated with chronic sleep maintenance insomnia characterized by nighttime awakenings among women with menopausal symptoms

OBJECTIVE

The aim of this study was to quantify the burden associated with chronic sleep maintenance insomnia characterized by nighttime awakenings (CINA) among women with menopausal symptoms.

METHODS

Data were obtained from the 2006 US National Health and Wellness Survey, an annual cross-sectional study of US adults 18 years or older. Analyses were limited to female respondents currently experiencing symptoms of menopause. The definition of CINA was experiencing nighttime awakenings at least twice per week for more than 1 month that have moderate to severe impact on daily life and not experiencing difficulty falling asleep. No insomnia was defined as not self-reporting insomnia, sleep difficulties, or sleep symptoms. Outcomes included resource utilization in the past 6 months, Work Productivity and Activity Impairment questionnaire, and Medical Outcomes Study Short-Form Health Survey (SF-8). Linear regression models were developed to assess the independent associations of CINA on outcomes, while adjusting for demographics and comorbidity.

RESULTS

Among women with menopausal symptoms, 141 met the criteria for CINA and 1,305 met the criteria for no insomnia. Adjusting for demographics and comorbidity, those experiencing CINA had 0.1 (P = 0.041) more emergency department visits, 20.8% (P < 0.001) greater activity impairment, and SF-8 physical and mental summary scores that were 4.7 (P < 0.001) and 5.4 (P < 0.001) points, respectively, lower than those of women who are not experiencing insomnia. Among women with menopausal symptoms employed full-time, those experiencing CINA had greater impairment while working (presenteeism; 17.3%, P < 0.001) and overall (16.1%, P < 0.001) than did those who are not experiencing insomnia.

CONCLUSIONS

Among women with menopausal symptoms, CINA in relative isolation was associated with a significant negative impact on healthcare utilization and its associated costs, health-related quality of life, and work productivity.

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.

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

The objective was to evaluate whether hormone therapy (HT) gives any benefit against the possible impairment of cognitive performance when challenged by acute sleep deprivation. Twenty postmenopausal women volunteered (age range 59-72 years, mean=64.4 years, SD=4.4): 10 HT users and 10 nonusers. Eleven young women served as a control group for the cognitive age effect (age range 20-26 years, mean age 23.1 years, SD=1.6). The subjects spent four consecutive nights at the sleep laboratory and were exposed to acute sleep deprivation of 40 h. Measures of attention (reaction speed and vigilance), alertness, and mood were administered every 2 h during the daytime and every hour during the sleep deprivation night. Postmenopausal women performed slower than young controls, whereas young controls made more errors. In HT users, the recovery night did not fully restore the performance in the simple and two-choice reaction time tasks, but in nonusers it did so. Sleep deprivation had a detrimental, yet reversible effect on vigilance in all groups. In all groups, sleepiness started to increase after 15 h of sleep deprivation and remained elevated in the morning after the recovery night. Prolonged wakefulness or HT had no effect on mood. In conclusion, sleep deprivation impaired cognitive performance in postmenopausal as well as young women. Postmenopausal women kept up their performance at the expense of reaction speed and young women at the expense of accuracy. One night was not enough for HT users to recover from sleep deprivation. Thus, HT gave no benefit in maintaining the attention and alertness during sleep deprivation.

Brief posturographic test as an indicator of fatigue

The purpose of the present paper was to analyze the efficiency of an abbreviated, albeit objective posturographic test as an indicator of fatigue. Posturography was measured in 10 healthy adults (age 18-33 years, male/female 7/3). Baseline posturographic measurements were taken for each subject. Later, a shorter (3-min) posturographic test was administered 12 times during 25 h of sleep deprivation. This was correlated with subjective assessment of fatigue using a questionnaire and cognitive performance assessed with a reaction time test (Psychomotor Vigilance Test). Although showing significant individual differences, the score of the abbreviated posturographic examination, normalized to each subject's baseline performance ('fatigue index') had a pronounced circadian pattern with a peak of instability in the early morning hours. Fatigue index was highly correlated with the cognitive test (r=0.80-0.90). A substantial, albeit weaker correlation was found between the fatigue index and the subjective fatigue scores (r=0.59-0.75). Fourier spectral analysis showed that low median sway (0.10-0.50 Hz), considered to be an expression of vestibular control, was most affected by fatigue. The study demonstrates that cognitive deterioration caused by fatigue can be objectively predicted by an abbreviated postural test of <or=3 min. This test is promising to be valid, reliable, and practicable, while being significantly correlated with physiological markers and validated cognitive measures of fatigue obtained by substantially more time-consuming and less convenient methods.