Aging does not affect the sleep endocrine response to total sleep deprivation in humans

Does sleep deprivation increase the vulnerability to acute psychosocial stress in young and older adults?

Sleep loss and psychosocial stress often co-occur in today's society, but there is limited knowledge on the combined effects. Therefore, this experimental study investigated whether one night of sleep deprivation affects the response to a psychosocial challenge. A second aim was to examine if older adults, who may be less affected by both sleep deprivation and stress, react differently than young adults. 124 young (18-30 years) and 94 older (60-72 years) healthy adults participated in one of four conditions: i. normal night sleep & Placebo-Trier Social Stress Test (TSST), ii. normal night sleep & Trier Social Stress Test, iii. sleep deprivation & Placebo-TSST, iv. sleep deprivation & TSST. Subjective stress ratings, heart rate variability (HRV), salivary alpha amylase (sAA) and cortisol were measured throughout the protocol. At the baseline pre-stress measurement, salivary cortisol and subjective stress values were higher in sleep deprived than in rested participants. However, the reactivity to and recovery from the TSST was not significantly different after sleep deprivation for any of the outcome measures. Older adults showed higher subjective stress, higher sAA and lower HRV at baseline, indicating increased basal autonomic activity. Cortisol trajectories and HRV slightly differed in older adults compared with younger adults (regardless of the TSST). Moreover, age did not moderate the effect of sleep deprivation. Taken together, the results show increased stress levels after sleep deprivation, but do not confirm the assumption that one night of sleep deprivation increases the responsivity to an acute psychosocial challenge.

Neurochemical regulation of sleep

This review summarizes recent developments in the field of sleep regulation, particularly in the role of hormones, and of synthetic GABA(A) receptor agonists. Certain hormones play a specific role in sleep regulation. A reciprocal interaction of the neuropeptides growth hormone (GH)-releasing hormone (GHRH) and corticotropin-releasing hormone (CRH) plays a key role in sleep regulation. At least in males GHRH is a common stimulus of non-rapid-eye-movement sleep (NREMS) and GH and inhibits the hypothalamo-pituitary adrenocortical (HPA) hormones, whereas CRH exerts opposite effects. Furthermore CRH may enhance rapid-eye-movement sleep (REMS). Changes in the GHRH:CRH ratio in favor of CRH appear to contribute to sleep EEG and endocrine changes during depression and normal ageing. In women, however, CRH-like effects of GHRH were found. Besides CRH somatostatin impairs sleep, whereas ghrelin, galanin and neuropeptide Y promote sleep. Vasoactive intestinal polypeptide appears to be involved in the temporal organization of human sleep. Beside of peptides, steroids participate in sleep regulation. Cortisol appears to promote REMS. Various neuroactive steroids exert specific effects on sleep. The beneficial effect of estrogen replacement therapy in menopausal women suggests a role of estrogen in sleep regulation. The GABA(A) receptor or GABAergic neurons are involved in the action of many of these hormones. Recently synthetic GABA(A) agonists, particularly gaboxadol and the GABA reuptake inhibitor tiagabine were shown to differ distinctly in their action from allosteric modulators of the GABA(A) receptor like benzodiazepines as they promote slow-wave sleep, decrease wakefulness and do not affect REMS.

Pituitary adenylate cyclase-activating peptide affects homeostatic sleep regulation in healthy young men

Pituitary adenylate cyclase-activating peptide (PACAP) is involved in autonomous regulation, including timekeeping, by its action on the suprachiasmatic nucleus and on neuroendocrine secretion, energy metabolism, and transmitter release. In particular, the interactions between PACAP and the glutamatergic system are well recognized. We compared the effect of intravenously administered PACAP to that of placebo in eight healthy male subjects. PACAP in a concentration of 4x12.5 microg was administered in a pulsatile fashion hourly between 2200 and 0100. Sleep EEG was recorded from 2300 to 1000, which was also the time when subjects were allowed to sleep. Blood samples were taken every 20 min between 2200 and 0700 for the determination of cortisol, GH, and prolactin. PACAP administration led to no changes in the macro-sleep structure as assessed according to standard criteria. Spectral analysis revealed a significant reduction in the theta-frequency range in the first 4-h interval and of the spindle frequency range in the second 4-h interval of the registration period. This was accompanied by an increase in the time constant tau of the physiological delta-power decline in the course of the night, i.e., a less pronounced dynamic of the reduction of delta-power with time. This was accompanied by a trend (P<0.1) toward decreased prolactin secretion in the first 4-h period of the night. No other changes in endocrine secretion were observed. We concluded that PACAP leads to a reduction of the dynamics of homeostatic sleep regulation and prolactin secretion. Both effects are the opposite of those seen after sleep deprivation but similar to the changes after napping, i.e., a reduced sleep propensity. This implies that PACAP might be involved in homeostatic sleep regulation.

Growth hormone-releasing hormone and corticotropin-releasing hormone enhance non-rapid-eye-movement sleep after sleep deprivation

The neuropeptides growth hormone (GH)-releasing hormone (GHRH) and corticotropin-releasing hormone (CRH) regulate sleep and nocturnal hormone secretion in a reciprocal fashion, at least in males. GHRH promotes sleep and GH and inhibits hypothalamo-pituitary-adrenocortical (HPA) hormones. CRH exerts opposite effects. In women, a sexual dimorphism was found because GHRH impairs sleep and stimulates HPA hormones. Sleep deprivation (SD) is the most powerful stimulus for inducing sleep. Studies in rodents show a key role of GHRH in sleep promotion after SD. The effects of GHRH and CRH on sleep-endocrine activity during the recovery night after SD are unknown. We compared sleep EEG, GH, and cortisol secretion between nights before and after 40 h of SD in 48 normal women and men aged 19-67 yr. During the recovery night, GHRH, CRH, or placebo were injected repetitively. After placebo during the recovery night, non-rapid-eye-movement sleep (NREMS) and rapid-eye-movement sleep (REMS) increased and wakefulness decreased compared with the baseline night. After GHRH, the increase of NREMS and the decrease of wakefulness were more distinct than after placebo. Also, after CRH, NREMS increased higher than after placebo, and a positive correlation was found between age and the baseline-related increase of slow-wave sleep. REMS increased after placebo and after GHRH, but not after CRH. EEG spectral analysis showed increases in the lower frequencies and decreases in the higher frequencies during NREMS after each of the treatments. Cortisol and GH did not differ between baseline and recovery nights after placebo. After GHRH, GH increased and cortisol decreased. Cortisol increased after CRH. No sex differences were found in these changes. Our data suggest that GHRH and CRH augment NREMS promotion after SD. Marked differences appear to exist in peptidergic sleep regulation between spontaneous and recovery sleep.

Sleep deprivation and hormone therapy in postmenopausal women

BACKGROUND AND PURPOSE

Sleep complaints increase after menopause, but literature on the effect of postmenopausal hormone therapy (HT) on sleep is controversial. The purpose of this study was to determine the effect of ageing and HT on sleep quality, assessed using polysomnography, and on the accuracy of the subjective estimation of sleep quality in women before and after sleep deprivation.

PATIENTS AND METHODS

Twenty postmenopausal women (aged 58-72 years) were recruited: 10 HT-users and 10 non-HT-users. Eleven young women (aged 20-26 years) served as controls. Polysomnography and subjective sleep quality were measured on four consecutive nights: adaptation, baseline, 40-h sleep deprivation and recovery.

RESULTS

Although the postmenopausal women slept worse than the controls at baseline, and in particular during the recovery night, their recovery response to sleep deprivation was well preserved. At baseline, HT-users had a shorter latency to rapid eye movement (REM) (P=0.043), with fewer awakenings from slow wave sleep (SWS) (P=0.029) but more from REM (P=0.033) than non-HT-users. During recovery, the HT-users had more stage 2 sleep (P=0.048) and less slow wave activity (SWA) in the first non-rapid eye movement (NREM) sleep episode (P=0.021) than the non-HT-users. The poor correlation between subjective and objective sleep quality at baseline became significant during recovery.

CONCLUSIONS

Although sleep in postmenopausal women was worse than in young controls, the recovery response following sleep deprivation was relatively well preserved. HT offered no significant advantage to sleep at baseline and slightly weakened the recovery response to prolonged wakefulness.

Homeostatic sleep response to naps is similar in normal elderly and young adults

Delta homeostatic regulation can be challenged by reducing delta need with daytime naps and measuring delta in post-nap sleep. We previously demonstrated that, after a late afternoon nap, young adults reduce the amount of delta in post-nap sleep by the amount in the nap. We compared homeostatic responses of 19 young adults (mean age 22.4 years) and 19 normal elderly subjects (mean age 71.4 years). Each participated in four separate 2-day sessions that consisted of a baseline night, a nap, and post-nap sleep. Nap times were 0900, 1200, 1500 and 1800 h. The 1800 h nap contained the largest amount of delta and produced the largest reduction in post-nap delta. The young and elderly groups respectively produced 28 and 24% of baseline delta in the 1800 h nap. Both groups showed equivalent delta regulation, reducing post-nap delta by 28 and 25%, respectively. In both age groups, the decrease in post-nap delta resulted from a reduced rate of delta production (power/min) and reduced non-rapid eye movement (NREM) sleep duration. Period-amplitude analysis showed that the reduction in power/min resulted from decreases in delta wave amplitude and incidence. None of the responses to nap challenges differed significantly across age groups nor were there gender differences or age by gender interactions. These results show that delta homeostatic responses to naps in the elderly parallel those of young subjects. REM sleep showed no homeostatic reductions following naps in either group. We believe that the striking differences in the delta and REM responses point to different biological roles of the two kinds of sleep.

Intravenous administration of the neuropeptide galanin has fast antidepressant efficacy and affects the sleep EEG

OBJECTIVE

Recently, we demonstrated that the intravenous administration of the neuropeptide galanin acts on the sleep EEG of healthy young subjects similar to sleep deprivation. As this effect could imply an antidepressive potency we studied the effect of intravenous galanin administration on psychopathology and sleep EEG in patients with depression.

METHODS

Galanin was administered to 10 patients with depression, who were on a stable dose of trimipramine. A placebo controlled double blind randomized design was used. Intravenous boli of galanin in a dose of 4 x 50 microg or placebo were administered hourly between 09:00 and 12:00 h. Galanin or placebo, respectively were administered on 2 days each. The sequence of the galanin or placebo days was randomized, allowing for various crossovers. The Hamilton depression rating scale score (HAMD) was performed 30 min before the first and 30 min after the last injection. The mean of the HAMD change between 08:30 and 12:30 h was chosen as primary efficacy variable. Sleep EEGs were recorded once post placebo treatment and once post verum treatment. In this case, recordings started at 23:00 h and ended at 07:00 h the next morning.

RESULTS

The HAMD-difference between 08:30 and 12:30 h was significantly greater at the days of galanin-treatment compared to placebo-treatment. MANOVA revealed a significant change in sleep-EEG parameters (p < 0.05), mainly due to an increase in REM-latency (p < 0.06).

CONCLUSION

The data provide preliminary evidence for an acute antidepressive efficacy of galanin, probably by a mechanism related to that of therapeutic sleep deprivation.

State markers of depression in sleep EEG: dependency on drug and gender in patients treated with tianeptine or paroxetine

Tianeptine enhances while paroxetine inhibits serotonin reuptake into neurons; however, both show an antidepressive action. A subgroup of 38 depressed patients from a drug trial comparing the efficacy of tianeptine with that of paroxetine was studied with regard to their effects on sleep regulation, especially in relation to treatment response. We recorded sleep EEGs at day 7 and day 42 after the start of treatment with either compound, which allows measurement of changes due to the antidepressive medication in relation to the duration of treatment. Spectral analysis of the non-REM sleep EEG revealed a strong decline in the higher sigma frequency range (14-16 Hz) in male treatment responders independent of medication, whereas nonresponders did not show marked changes in this frequency range independent of gender. The patients receiving paroxetine showed less REM sleep and more intermittent wakefulness compared to the patients receiving tianeptine. REM density after 1 week of treatment was a predictor of treatment response in the whole sample. Psychopathological features with regard to the score in single items of the HAMD revealed predictive markers for response, some of which were opposite in the gender groups, especially those related to somatic anxiety. Changes in REM density were inversely correlated to the changes in HAMD in the paroxetine, but not the tianeptine, group. Our data suggest the importance of taking gender into account in the study of the biological effects of drugs. The study further points to the importance of the higher sigma frequency range in the sleep EEG of non-REM sleep and REM density as a marker of treatment response.

Increase in amino acids in the pons after sleep deprivation: a pilot study using proton magnetic resonance spectroscopy

Total sleep deprivation (TSD) is an efficient method to relieve depression. An involvement of GABAergic and glutamatergic neurotransmission in the pathophysiology of depression and the mechanism of action of TSD has been suggested. To directly assess the content of GABA, glutamate (Glu) and glutamine (Gln) before and after TSD, we estimated their concentrations in four brain regions in six healthy subjects using proton magnetic resonance spectroscopy. The unresolved estimate of GABA, Glu and Gln, as well as GABA and Gln were increased in the pons after 24 h of TSD, the effect being prominent in three subjects. There were no significant changes in the hypothalamus, thalamus or parietooccipital cortex. These preliminary data support earlier animal data and indirect findings in humans suggesting that GABA and Gln, especially in the pontine structures, may play a key role in the mechanism of TSD.

Sleep and the hypothalamo-pituitary-adrenocortical system

The intention of this review is to summarize the current knowledge on the bidirectional interaction between sleep EEG and the secretion of corticotropin (ACTH) and cortisol. The administration of various hypothalamic-pituitary- adrenocortical (HPA) hormones and their antagonists exerts specific sleep-EEG changes in several species including humans. It is well documented that corticotropin releasing hormone (CRH) impairs sleep and enhances vigilance. In addition, it may promote REM sleep. Changes in the growth hormone-releasing hormone (GHRH):CRH ratio in favour of CRH appear to contribute to shallow sleep, elevated cortisol levels and blunted GH in depression and ageing. On the other hand, in women GHRH appears to exert CRH-like effects on sleep. Acute cortisol administration increases slow-wave sleep (SWS) and GH, probably due to feedback inhibition of CRH, and inhibits REM sleep. With the mixed glucocorticoid and progesterone receptor antagonist mifepriston sleep is disrupted. Subchronic administration of the glucocorticoid agonist methylprednisolone desinhibited REM sleep. A synergism of elevated CRH and cortisol activity may contribute to REM disinhibition during depression. Also ACTH and vasopressin modulate sleep specifically but their physiological role remains unclear. For example acute icv vasopressin enhances wakefulness in rats, whereas its long-term administration increases SWS in the elderly. In various studies the interaction of sleep EEG and HPA hormones has been investigated at the baseline, after manipulation of sleep-wake behaviour and after environmental changes. Most studies agree that the circadian pattern of cortisol is relatively independent from sleep and environmental influences. Some data suggest a major effect of light on cortisol secretion. Sleeping is widely associated with blunting and awakenings are linked with increases of HPA hormones.

Effect of the GABAA agonist gaboxadol on nocturnal sleep and hormone secretion in healthy elderly subjects

Aging is associated with a dramatic decrease in sleep intensity and continuity. The selective GABA(A) receptor agonist gaboxadol has been shown to increase non-REM sleep and the duration of the non-REM episodes in rats and sleep efficiency in young subjects and to enhance low-frequency activity in the electroencephalogram (EEG) within non-REM sleep in both rats and humans. In this double-blind, placebo-controlled study, we investigated the influence of an oral dose of 15 mg of gaboxadol on nocturnal sleep and hormone secretion (ACTH, cortisol, prolactin, growth hormone) in 10 healthy elderly subjects (6 women). Compared with placebo, gaboxadol did not affect endocrine activity but significantly reduced perceived sleep latency, elevated self-estimated total sleep time, and increased sleep efficiency by decreasing intermittent wakefulness and powerfully augmented low-frequency activity in the EEG within non-REM sleep. These findings indicate that gaboxadol is able to increase sleep consolidation and non-REM sleep intensity, without disrupting REM sleep, in elderly individuals and that these effects are not mediated by a modulation of hormone secretion.

The GABA uptake inhibitor tiagabine promotes slow wave sleep in normal elderly subjects

Aging is associated with a dramatic decrease in slow wave sleep (SWS) and sleep consolidation. Previous studies revealed that various GABA(A) agonists and the GABA uptake inhibitor tiagabine augment slow frequency components in the EEG within non-REM sleep, and thus promote deep sleep in young individuals and/or rats. In the present double-blind, placebo-controlled study, we assessed the effect of a single oral dose of 5 mg tiagabine on nocturnal sleep in ten healthy elderly volunteers (6 females). During the placebo night the subjects displayed a low sleep efficiency, due to high amounts of intermittent wakefulness, and little SWS. Tiagabine significantly increased sleep efficiency, tendentially decreased wakefulness and prominently increased both SWS and low-frequency activity in the EEG within non-REM sleep. The present findings demonstrate that tiagabine increases sleep quality in aged subjects. Moreover, the effects of tiagabine closely match those evoked by the GABA(A) agonist gaboxadol in young subjects and indicate that such compounds may have prospects in the treatment of sleep disturbances, particularly of those commonly occurring in the elderly.