Sex differences in sleep and sleep-dependent learning in abstinent cocaine users

Psychostimulant Use Disorder, an Unmet Therapeutic Goal: Can Modafinil Narrow the Gap?

The number of individuals affected by psychostimulant use disorder (PSUD) has increased rapidly over the last few decades resulting in economic, emotional, and physical burdens on our society. Further compounding this issue is the current lack of clinically approved medications to treat this disorder. The dopamine transporter (DAT) is a common target of psychostimulant actions related to their use and dependence, and the recent availability of atypical DAT inhibitors as a potential therapeutic option has garnered popularity in this research field. Modafinil (MOD), which is approved for clinical use for the treatment of narcolepsy and sleep disorders, blocks DAT just like commonly abused psychostimulants. However, preclinical and clinical studies have shown that it lacks the addictive properties (in both behavioral and neurochemical studies) associated with other abused DAT inhibitors. Clinical availability of MOD has facilitated its off-label use for several psychiatric disorders related to alteration of brain dopamine (DA) systems, including PSUD. In this review, we highlight clinical and preclinical research on MOD and its R-enantiomer, R-MOD, as potential medications for PSUD. Given the complexity of PSUD, we have also reported the effects of MOD on psychostimulant-induced appearance of several symptoms that could intensify the severity of the disease (i.e., sleep disorders and impairment of cognitive functions), besides the potential therapeutic effects of MOD on PSUD.

Interaction between cocaine use and sleep behavior: A comprehensive review of cocaine's disrupting influence on sleep behavior and sleep disruptions influence on reward seeking

Dopamine, orexin (hypocretin), and adenosine systems have dual roles in reward and sleep/arousal suggesting possible mechanisms whereby drugs of abuse may influence both reward and sleep/arousal. While considerable variability exists across studies, drugs of abuse such as cocaine induce an acute sleep loss followed by an immediate recovery pattern that is consistent with a normal response to loss of sleep. Under more chronic cocaine exposure conditions, an abnormal recovery pattern is expressed that includes a retention of sleep disturbance under withdrawal and into abstinence conditions. Conversely, experimentally induced sleep disturbance can increase cocaine seeking. Thus, complementary, sleep-related therapeutic approaches may deserve further consideration along with development of non-human models to better characterize sleep disturbance-reward seeking interactions across drug experience.

Sex and Menstrual Phase Influences on Sleep and Memory

Purposes of Review

This review highlights the effect of sex differences in sleep mediated memory consolidation and cognitive performance. In addition, the role of menstrual cycle and the fluctuating level of sexual hormones (mainly oestrogen and progesterone) are stressed.

Recent Findings

The literature indicates that sex hormones mediate and orchestrate the differences observed in performance of females in comparison with males in a variety of tasks and can also be related to how sleep benefits cognition. Although the exact mechanism of such influence is not clear, it most likely involves differential activation of brain areas, sensitivity to neuromodulators (mainly oestrogen), circadian regulation of sleep and temperature, as well as modification of strategies to solve tasks across the menstrual cycle.

Summary

With the evidence presented here, we hope to encourage researchers to develop appropriate paradigms to study the complex relationship between menstrual cycle, sleep (its regulation, architecture and electrophysiological hallmarks) and performance in memory and other cognitive tasks.

Sleep time differs among people who co-use cocaine and cannabis compared to people who only use cocaine

OBJECTIVE

People who use cocaine experience numerous sleep problems and often use cannabis to mitigate these problems. However, co-using cocaine and cannabis may result in worse sleep outcomes when compared to using cocaine only. The current study examined group differences in subjective sleep outcomes among people who use cocaine and people who co-use cocaine and cannabis.

METHODS

Participants were 82 individuals with cocaine use disorder who were enrolled in a randomized clinical trial for cocaine treatment. Sleep outcomes, assessed at baseline prior to treatment, were measured with the Saint Mary's Hospital Sleep Questionnaire and included total sleep time, perceived sleep quality, difficulty falling asleep, and daytime alertness. Analysis of covariance and Kruskal-Wallis tests were used to compare sleep outcomes between participants with urine samples that tested positive for both cocaine and cannabis at baseline, those who tested positive for cocaine only, and those who tested negative for all drugs.

RESULTS

Total reported sleep time was highest among those with a drug negative urine, followed by those with a cocaine positive urine and those who tested positive for cocaine and cannabis. There were no differences in perceived sleep quality, difficulty falling asleep, or daytime alertness between groups.

CONCLUSIONS

People who co-use cocaine and cannabis may report reduced sleep time relative to those who only use cocaine. Co-use of cannabis may exacerbate sleep difficulties in people who use cocaine by decreasing total sleep time, although it is important to note that the groups each reported similar sleep quality. Implications for treatment and directions for future research are discussed.

Sleep Perception and Misperception in Chronic Cocaine Users During Abstinence

Study Objectives

During abstinence, chronic cocaine users experience an objective worsening of sleep that is perceived as qualitatively improving. This phenomenon has been termed "occult insomnia." The objective of this study was to determine whether chronic cocaine users experience positive sleep state misperception during abstinence.

Methods

Forty-three cocaine-dependent persons were admitted to an inpatient research facility for 12 days and 11 nights to participate in a treatment study of modafinil. Polysomnographic sleep recordings were performed on study nights 3, 4, 10, and 11, when participants were on average 1 and 2 weeks abstinent from cocaine. Participants also completed sleep diary questionnaires every evening before bed and every morning upon awakening. Polysomnographic and sleep diary measurements of total sleep time, sleep latency, time awake after sleep onset, and time in bed after final awakening were compared.

Results

Chronic cocaine users accurately reported total sleep time after 1 week of abstinence but overreported total sleep time by an average of 40 min after 2 weeks of abstinence. Underestimating sleep latency and time spent awake after sleep onset were responsible for this difference.

Conclusions

Positive sleep state misperception is revealed in chronic cocaine users after 2 weeks of abstinence and is consistent with the previously identified "occult insomnia" in this population.

Altered activity-based sleep measures in rhesus monkeys following cocaine self-administration and abstinence

BACKGROUND

Impairments in sleep and cognitive function have been observed in patients with substance abuse disorders and may be potential factors contributing to drug relapse. In addition, sleep disruption may itself contribute to cognitive deficits. In the present study we examined the impact of prolonged cocaine self-administration and abstinence on actigraphy-based measures of night-time activity in rhesus macaques as an inferential measure of sleep, and determined whether sleep-efficiency correlated with cognitive impairments in the same subjects on drug free days.

METHODS

Actigraphy data was obtained from a group of rhesus macaques intravenously self-administering cocaine (n=6) and a control group (n=5). Periods were evaluated during which the mean cumulative doses of cocaine were 3.0+0.0 and 4.5+0.2mg/kg/day for 4days (Tuesday-Thursday) each week.

RESULTS

Actigraphy-based sleep efficiency decreased during days of cocaine self-administration in a dose-dependent manner. Consistent with this observation, sleep became more fragmented. Activity-based sleep efficiency normalized during the weekend without cocaine prior to cognitive assessment on Monday. The magnitude of activity-based sleep disruption during self-administration did not correlate with the level of cognitive impairment on drug free days. With continued self-administration, the impact of cocaine on activity-based sleep efficiency declined indicating the development of tolerance.

CONCLUSIONS

Cocaine self-administration disrupted sleep efficiency in rhesus macaques as measured by actigraphy, but normalized quickly in the absence of cocaine. The cognitive impairment observed on drug free days was unlikely to be related to disruption of the nightly activity patterns on days of cocaine self-administration.

Polysomnographic measures of sleep in cocaine dependence and alcohol dependence: Implications for age-related loss of slow wave, stage 3 sleep

BACKGROUND AND AIMS

Sleep disturbance is a prominent complaint in cocaine and alcohol dependence. This controlled study evaluated differences of polysomnographic (PSG) sleep in cocaine- and alcohol-dependent subjects, and examined whether substance dependence interacts with age to alter slow wave sleep and rapid eye movement (REM) sleep.

DESIGN

Cross-sectional comparison.

SETTING

Los Angeles and San Diego, CA, USA.

PARTICIPANTS

Abstinent cocaine-dependent subjects (n = 32), abstinent alcohol-dependent subjects (n = 73) and controls (n = 108); mean age 40.3 years recruited 2005-12.

MEASUREMENTS

PSG measures of sleep continuity and sleep architecture primary outcomes of Stage 3 sleep and REM sleep. Covariates included age, ethnicity, education, smoking, body mass index and depressive symptoms.

FINDINGS

Compared with controls, both groups of substance dependent subjects showed loss of Stage 3 sleep (P < 0.001). A substance dependence × age interaction was found in which both cocaine- and alcohol-dependent groups showed loss of Stage 3 sleep at an earlier age than controls (P < 0.05 for all), and cocaine-dependent subjects showed loss of Stage 3 sleep at an earlier age than alcoholics (P < 0.05). Compared with controls, REM sleep was increased in both substance-dependent groups (P < 0.001), and cocaine and alcohol dependence were associated with earlier age-related increase in REM sleep (P < 0.05 for all).

CONCLUSIONS

Cocaine and alcohol dependence appear to be associated with marked disturbances of sleep architecture, including increased rapid eye movement sleep and accelerated age-related loss of slow wave, Stage 3 sleep.

Modafinil and sleep architecture in an inpatient-outpatient treatment study of cocaine dependence

OBJECTIVE

To determine whether the increase in slow-wave sleep associated with modafinil treatment in chronic cocaine users mediates improved clinical outcomes.

METHOD

57 cocaine dependent participants were randomized to receive modafinil 400mg or placebo daily during a period of inpatient treatment followed by six weeks of outpatient treatment. Participants underwent polysomnographic sleep recording during inpatient treatment prior to and after starting modafinil. Outpatient treatment consisted of weekly cognitive behavioral therapy. Contingency management was used to promote participation in treatment and research demands, including thrice weekly visits during the outpatient phase for urine toxicology screens and other assessments. The primary clinical outcome was the percent of urine toxicology screens that were negative for cocaine.

RESULTS

Modafinil treatment was associated with a higher mean percentage (52% vs. 26%) of cocaine-free urine screens (p=0.02) and an increase in N3 sleep time (p=0.002). The change in N3 sleep time mediated the higher rate of cocaine-free urine screens. Modafinil treatment was also associated with more consecutive days abstinent during outpatient treatment, greater survival of abstinence, higher daily rates of abstinence, and less sleep degradation typically associated with abstinence from chronic cocaine use.

CONCLUSIONS

Morning-dosed modafinil improves slow-wave sleep in abstinent cocaine users in the inpatient setting, and this effect is a statistical mediator of improved clinical outcomes associated with continued modafinil treatment. The high rates of abstinence achieved in this trial suggest that promoting healthy sleep physiology in an inpatient setting may be important in the effective treatment of cocaine dependence.

A multistudy analysis of the effects of early cocaine abstinence on sleep

OBJECTIVE

To describe the sleep patterns of early cocaine abstinence in chronic users by polysomnographic and subjective measures.

METHODS

28 cocaine-dependent participants (ages 24-55) underwent polysomnographic sleep (PSG) recording on the 1st, 2nd and 3rd weeks of abstinence on a research dedicated inpatient facility. Objective measures of total sleep time, total REM time, slow wave sleep, sleep efficiency and a subjective measure (sleep quality) along with demographic data were collected from three different long term research studies over a five year period. Data were reanalysed to allow greater statistical power for comparisons.

RESULTS

Progressive weeks of abstinence had main effects on all assessed PSG sleep measures showing decreased total sleep time, REM sleep, stages 1 and 2 sleep, and sleep efficiency; increases in sleep onset and REM latencies and a slight increase in slow-wave sleep time were also present. Total sleep time and slow wave sleep were negatively associated with years of cocaine use. Total sleep time was positively associated with the amount of current ethanol use. Sex differences were found with females having more total REM time and an increase at a near significance level in slow wave sleep. Subjective measures were reported as improving with increasing abstinence over the same time period.

CONCLUSIONS

Chronic cocaine users show a general deterioration in objective sleep measures over a three-week period despite an increase in subjective overall sleep quality providing further evidence for "occult insomnia" during early cocaine abstinence.

Polysomnogram changes in marijuana users who report sleep disturbances during prior abstinence

BACKGROUND

Abrupt discontinuation of heavy marijuana (MJ) use is associated with self-reports of sleep difficulty. Disturbed sleep is clinically important because MJ users experiencing sleep problems may relapse to MJ use to improve their sleep quality. Few studies have used polysomnography (PSG) to characterize changes in sleep architecture during abrupt abstinence from heavy MJ use.

METHODS

We recorded PSG measures on nights 1, 2, 7, 8, and 13 after abrupt MJ discontinuation in 18 heavy MJ users residing in an inpatient unit.

RESULTS

Across abstinence, Total Sleep Time (TST), Sleep Efficiency (SEff), and amount of REM sleep declined, while Wake after Sleep Onset (WASO) and Periodic Limb Movements (PLM) increased. Furthermore, quantity (joints/week) and duration (years) of MJ use were positively associated with more PLMs.

CONCLUSION

The treatment of sleep disturbance is a potential target for the management of cannabis use disorders since poor sleep could contribute to treatment failure in heavy MJ users.

Normalizing effects of modafinil on sleep in chronic cocaine users

OBJECTIVE

The purpose of the present study was to determine the effect of morning-dosed modafinil on sleep and daytime sleepiness in chronic cocaine users.

METHOD

Twenty cocaine-dependent participants were randomly assigned to receive modafinil, 400 mg (N=10), or placebo (N=10) every morning at 7:30 a.m. for 16 days in an inpatient, double-blind randomized trial. Participants underwent polysomnographic sleep recordings on days 1 to 3, 7 to 9, and 14 to 16 (first, second, and third weeks of abstinence). The Multiple Sleep Latency Test was performed at 11:30 a.m., 2:00 p.m., and 4:30 p.m. on days 2, 8, and 15. For comparison of sleep architecture variables, 12 healthy comparison participants underwent a single night of experimental polysomnography that followed 1 night of accommodation polysomnography.

RESULTS

Progressive abstinence from cocaine was associated with worsening of all measured polysomnographic sleep outcomes. Compared with placebo, modafinil decreased nighttime sleep latency and increased slow-wave sleep time in cocaine-dependent participants. The effect of modafinil interacted with the abstinence week and was associated with longer total sleep time and shorter REM sleep latency in the third week of abstinence. Comparison of slow-wave sleep time, total sleep time, and sleep latency in cocaine-dependent and healthy participants revealed a normalizing effect of modafinil in cocaine-dependent participants. Modafinil was associated with increased daytime sleep latency, as measured by the Multiple Sleep Latency Test, and a nearly significant decrease in subjective daytime sleepiness.

CONCLUSIONS

Morning-dosed modafinil promotes nocturnal sleep, normalizes sleep architecture, and decreases daytime sleepiness in abstinent cocaine users. These effects may be relevant in the treatment of cocaine dependence.