Impact of menstrual cycle phase on endocrine effects of partial sleep restriction in healthy women

Interaction of sleep and emotion across the menstrual cycle

Menstruating individuals experience an increased risk for sleep and affective disorders, attributed in part to monthly oscillations in sex hormones. Emotional functioning and sleep continuity worsens during the perimenstrual phase of the menstrual cycle. This study examined the interactive effects of sleep, menstrual phase, and emotion in healthy women. Participants (N = 51, 43% Caucasian) aged 18-35 (m = 24 years) completed actigraphy and daily sleep/emotion diaries over two menstrual cycles (m days = 51.29). Diary and actigraphic total wake time at night (TWT) and daily ratings of positive and negative affect were compared across four phases of the menstrual cycle: perimenstrual, mid-follicular, periovulatory, and mid-luteal. Relationships between phase, sleep, and emotion were estimated using multistep hierarchical linear modelling. Mean menstrual cycle length was 28.61 ± 2.69 days. Perimenstrual phase positively predicted anger (p < 0.001) but no other emotions. Additionally, the perimenstrual phase predicted higher rates of TWT, such that diary TWT was 8-16 min longer during the perimenstrual (m = 67.54, SE = 3.37) compared to other phases (p < 0.001). Actigraphic TWT was also increased by 4-7 min (m = 61.54, SE = 3.37) in the perimenstrual phase (p < 0.001). Positive emotions were 0.05-0.10 points lower (p = 0.006-0.02) when TWT was greater in the perimenstrual phase. Greater rates of anger and sleep disruption were seen during the perimenstrual phase compared with other phases. When poor sleep occurred during the perimenstrual phase individuals reported reduced positive emotions. Reducing perimenstrual sleep disruptions may be an important intervention target for those at risk for affective disorders.

Determining menstrual cycle phase: An empirical examination of methodologies and recommendations for improvement in behavioral and brain sciences

The recent decade has brought an exciting proliferation of behavioral, psychological and neuroscientific research involving the menstrual cycle. However, the reliability and validity of many popular methodologies for determining menstrual cycle phase lack empirical examination. These under-investigated methods include: (1) predicting menstrual cycle phase using self-report information only (e.g., "count" methods), (2) utilizing ovarian hormone ranges to determine menstrual cycle phase, and (3) using ovarian hormone changes from limited measurements (e.g., two time points) to determine menstrual cycle phase. In the current study, we examine the accuracy of these methods for menstrual cycle phase determination using 35-day within-person assessments of circulating ovarian hormones from 96 females across the menstrual cycle. Findings indicate that all three common methods are error-prone, resulting in phases being incorrectly determined for many participants, with Cohen's kappa estimates ranging from -0.13 to 0.53 indicating disagreement to only moderate agreement depending on the comparison. Such methodological challenges are surmountable through careful study design, more frequent hormone assays (when possible), and utilization of sophisticated statistical methods. With increased methodological rigor in behavioral, psychological and neuroscientific research, the field will be poised to detect biobehavioral correlates of ovarian hormone fluctuations for the betterment of the mental health and wellbeing of millions of females.

Associations of chronotype and insomnia with menstrual problems in newly employed nurses at university hospitals in the Republic of Korea

Background

Dysmenorrhea and menstrual cycle changes occur in women working shifts. Circadian rhythm disruption and sleep disturbances associated with shift work leads to health problems. We identified chronotypes and the occurrence of insomnia among newly employed university hospital nurses and investigated the association of these factors with menstrual problems.

Methods

We conducted pre-placement health examinations for shift workers using self-reported questionnaires between 2018 and 2020. A total of 463 nurses were included in the study. Sociodemographic data, shift work experience, and information on insomnia were collected from health examination data. In addition, details regarding chronotype, dysmenorrhea, irregular and abnormal menstrual cycles, amenorrhea, and contraceptive use were obtained from the questionnaire. Multiple logistic regression analysis was performed to study the association between chronotype, insomnia, and menstrual problems after controlling for age, body mass index, contraceptive use, amenorrhea, and prior shift work.

Results

The prevalence rates of dysmenorrhea, irregular menstrual cycles, and longer menstrual cycles were 23.8%, 14.9%, and 4.1%, respectively. The risk of dysmenorrhea increased in the evening-type (odds ratio [OR]: 3.209; 95% confidence interval [CI]: 1.685-6.113) and those with insomnia (OR: 1.871; 95% CI: 1.074-3.261). Additionally, the risk of an irregular menstrual cycle (OR: 2.698; 95% CI: 1.167-6.237) increased in the evening-type, and the risk of a longer menstrual cycle (OR: 4.008; 95% CI: 1.354-11.864) increased in individuals with insomnia.

Conclusions

Our findings suggest that dysmenorrhea is promoted in the evening-type and insomnia individuals. There may be an increased risk of irregular menstrual cycles among evening-type nurses and an increased risk of longer menstrual cycles among those with insomnia. Therefore, factors such as evening-type and insomnia should be considered for the prevention of menstrual problems in women performing shift work.

Hypnotic enhancement of slow-wave sleep increases sleep-associated hormone secretion and reduces sympathetic predominance in healthy humans

Sleep is important for normal brain and body functioning, and for this, slow-wave sleep (SWS), the deepest stage of sleep, is assumed to be especially relevant. Previous studies employing methods to enhance SWS have focused on central nervous components of this sleep stage. However, SWS is also characterized by specific changes in the body periphery, which are essential mediators of the health-benefitting effects of sleep. Here we show that enhancing SWS in healthy humans using hypnotic suggestions profoundly affects the two major systems linking the brain with peripheral body functions, i.e., the endocrine and the autonomic nervous systems (ANS). Specifically, hypnotic suggestions presented at the beginning of a 90-min afternoon nap to promote subsequent SWS strongly increased the release of growth hormone (GH) and, to a lesser extent, of prolactin and aldosterone, and shifted the sympathovagal balance towards reduced sympathetic predominance. Thus, the hypnotic suggestions induced a whole-body pattern characteristic of natural SWS. Given that the affected parameters regulate fundamental physiological functions like metabolism, cardiovascular activity, and immunity, our findings open up a wide range of potential applications of hypnotic SWS enhancement, in addition to advancing our knowledge on the physiology of human SWS.

The hypnotic enhancement of slow wave sleep, the deepest stage of sleep, goes beyond the central nervous system, causing changes at the level of the endocrine and the autonomic nervous systems.

Sleep quality and neurohormonal and psychophysiological accompanying factors in adolescents with depressive disorders: study protocol

BACKGROUND

Depressive disorders are common mental health problems during adolescence. Many adolescents with depression describe difficulties with sleeping. Findings of previous studies regarding changes in objective sleep quality in adolescents with depressive disorders are heterogeneous.

AIMS

This study aims to investigate differences in objective and subjective sleep quality between adolescents with depressive disorders and healthy peers, and to evaluate if potential changes in sleep occur concurrently with changes in the release of cortisol and alpha-amylase after awakening.

METHOD

This non-interventional parallel study examines correlations between depressive disorders, sleep quality and release of stress hormones. Sleep quality in the past 2 weeks, severity of depressive symptoms, psychiatric comorbidities and stress response of 30 adolescents with depressive disorders and 30 healthy controls (N = 60) are assessed via questionnaires. In participants' home environments, the objective sleep quality of seven consecutive nights is measured by sleep accelerometry. After awakening, participants answer sleep questionnaires to examine the subjective sleep quality of those nights. Furthermore, salivary cortisol and alpha-amylase are measured three times after awakening (+0 min, +30 min and +45 min after awakening).

CONCLUSIONS

Sleep is an important factor for prognosis and well-being in adolescents with depression. The results of this study can be highly valuable to integrate a more detailed examination of sleep quality and sleeping impairments in the treatment of adolescent depressive disorders.

Higher Circulating Cortisol in the Follicular vs. Luteal Phase of the Menstrual Cycle: A Meta-Analysis

Although results of animal research show that interactions between stress and sex hormones are implicated in the development of affective disorders in women, translation of these findings to patients has been scarce. As a basic step toward advancing this field of research, we analyzed findings of studies which reported circulating cortisol levels in healthy women in the follicular vs. luteal phase of the menstrual cycle. We deemed this analysis critical not only to advance our understanding of basic physiology, but also as an important contrast to the findings of future studies evaluating stress and sex hormones in women with affective disorders. We hypothesized that cortisol levels would be lower in the follicular phase based on the proposition that changes in levels of potent GABAergic neurosteroids, including allopregnanolone, during the menstrual cycle dynamically change in the opposite direction relative to cortisol levels. Implementing strict inclusion criteria, we compiled results of high-quality studies involving 778 study participants to derive a standardized mean difference between circulating cortisol levels in the follicular vs. luteal phase of the menstrual cycle. In line with our hypothesis, our meta-analysis found that women in the follicular phase had higher cortisol levels than women in the luteal phase, with an overall Hedges' g of 0.13 (p < 0.01) for the random effects model. No significant between-study difference was detected, with the level of heterogeneity in the small range. Furthermore, there was no evidence of publication bias. As cortisol regulation is a delicate process, we review some of the basic mechanisms by which progesterone, its potent metabolites, and estradiol regulate cortisol output and circulation to contribute to the net effect of higher cortisol in the follicular phase.

The menstrual cycle associated with insomnia in newly employed nurses performing shift work: a 12-month follow-up study

PURPOSE

This study aimed to investigate whether insomnia among newly-employed shift-working nurses is associated with menstrual cycle irregularity.

METHODS

We followed 287 nurses employed between 2015 and 2016 for 12 months. An Insomnia Severity Index (ISI) was completed to determine levels of insomnia 6 months after beginning work. At baseline and at 12-month follow-up, menstrual cycle information was obtained using clinical interviews. We analyzed baseline data separately by prevalence (participants with menstrual irregularity, n = 287) and incidence (participants with no reported menstrual irregularity, n = 238).

RESULTS

In a multivariate logistic regression analysis, including age, body mass index, and physical activity, insomnia was associated with a 2.05-fold increase in the odds of newly developing menstrual cycle irregularity compared with not having insomnia [odds ratio (OR) 2.05, 95% confidence interval (CI) 1.12-3.77]. Insomnia was associated with a 3.05-fold increase in the prevalence of menstrual cycle irregularity compared with not having insomnia (OR 3.05, 95% CI 1.81-5.13). As the ISI score increased, both the incidence and prevalence odds of menstrual cycle irregularity tended to increase.

CONCLUSIONS

Insomnia can induce menstrual cycle irregularity among nurses working shifts, and insomnia may have an important role in the pathway from shift work to menstrual dysfunction, aside from the possible effects of circadian rhythm disruption.

Acute Sleep Restriction Has Differential Effects on Components of Attention

Inadequate nightly sleep duration can impair daytime functioning, including interfering with attentional and other cognitive processes. Current models posit that attention is a complex function regulated by several separate, but interacting, neural systems responsible for vigilance, orienting, and executive control. However, it is not clear to what extent each of these underlying component processes is affected by sleep loss. The purpose of this study was to evaluate the effects of acute sleep restriction on these attentional components using the Dalhousie Computerized Attention Battery (DalCAB). DalCAB tasks were administered to healthy women (aged 19-25 years) on two consecutive mornings: once after a night with 9 h time in bed (TIB), and once again after either another night with 9 h TIB (control condition, n = 19) or after a night with 3 h TIB (sleep restriction condition, n = 20). Self-ratings of sleepiness and mood were also obtained following each sleep condition. Participants showed increases in self-reported sleepiness and fatigue after the second night only in the sleep restriction group. Sleep restriction primarily affected processing speed on tasks measuring vigilance; however, performance deficits were also observed on some measures of executive function (e.g., go/no-go task, flanker task, working memory). Tasks assessing orienting of attention were largely unaffected. These results indicate that acute sleep restriction has differential effects on distinct components of attention, which should be considered in modeling the impacts of sleep loss on the underlying attentional networks.

Sex differences in age-related changes in the sleep-wake cycle

Age-related changes in sleep and circadian regulation occur as early as the middle years of life. Research also suggests that sleep and circadian rhythms are regulated differently between women and men. However, does sleep and circadian rhythms regulation age similarly in men and women? In this review, we present the mechanisms underlying age-related differences in sleep and the current state of knowledge on how they interact with sex. We also address how testosterone, estrogens, and progesterone fluctuations across adulthood interact with sleep and circadian regulation. Finally, we will propose research avenues to unravel the mechanisms underlying sex differences in age-related effects on sleep.

Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparison

Smartphones deliver light to users through Light Emitting Diode (LED) displays. Blue light is the most potent wavelength for sleep and mood. This study investigated the immediate effects of smartphone blue light LED on humans at night. We investigated changes in serum melatonin levels, cortisol levels, body temperature, and psychiatric measures with a randomized, double-blind, cross-over, placebo-controlled design of two 3-day admissions. Each subject played smartphone games with either conventional LED or suppressed blue light from 7:30 to 10:00PM (150 min). Then, they were readmitted and conducted the same procedure with the other type of smartphone. Serum melatonin levels were measured in 60-min intervals before, during and after use of the smartphones. Serum cortisol levels and body temperature were monitored every 120 min. The Profile of Mood States (POMS), Epworth Sleepiness Scale (ESS), Fatigue Severity Scale (FSS), and auditory and visual Continuous Performance Tests (CPTs) were administered. Among the 22 participants who were each admitted twice, use of blue light smartphones was associated with significantly decreased sleepiness (Cohen's d = 0.49, Z = 43.50, p = 0.04) and confusion-bewilderment (Cohen's d = 0.53, Z = 39.00, p = 0.02), and increased commission error (Cohen's d = -0.59, t = -2.64, p = 0.02). Also, users of blue light smartphones experienced a longer time to reach dim light melatonin onset 50% (2.94 vs. 2.70 h) and had increases in body temperature, serum melatonin levels, and cortisol levels, although these changes were not statistically significant. Use of blue light LED smartphones at night may negatively influence sleep and commission errors, while it may not be enough to lead to significant changes in serum melatonin and cortisol levels.

Cortisol awakening response is blunted and pain perception is increased during menses in cyclic women

BACKGROUND AND AIMS

The incidence of menstrual symptoms is reported to be as high as 90% in cyclic women. These symptoms, including anxiety and pain, might be associated with cortisol, as its receptors are widely distributed in the brain areas associated with behavior. Therefore, the current study aimed to assess the cortisol awakening response (CAR) throughout the menstrual cycle and correlate it with pain perception and trait anxiety.

MATERIALS AND METHODS

CAR was assessed by measuring salivary cortisol at 0, 15, 30, and 60min following awakening in the same women (n=59, age 22.2±0.37years) at various stages of the menstrual cycle (menses, midcycle, luteal and premenstrual phases). Progesterone and estradiol concentrations were also determined in saliva samples to assess cyclic changes. Self-reported pain, trait anxiety, and menstrual symptoms were assessed by visual analog scale (VAS), state-trait anxiety inventory (STAI-T), and the Daily Record of Severity of Problems (DRSP), respectively.

RESULTS

Estradiol was significantly elevated during the midcycle period and remained high during the early luteal phase (p<0.05). Progesterone was increased during the luteal phase (p<0.05). Post-awakening cortisol values increased during midcycle, luteal phase, and premenstrual phase (p<0.05, classical CAR), but not during the menses (p>0.05, blunted or flat CAR). Positive and significant correlations were found between cortisol and estradiol (R²=0.322; p=0.000), cortisol and progesterone (R²=0.156; p=0.000), and estradiol and progesterone (R²=0.349; p=0.001). Premenstrual symptom scores were higher in the menses and premenstrual phases than in the midcycle and luteal phases (p<0.001). Pain perception was the highest during the menses followed by the premenstrual phase (p<0.01).

CONCLUSIONS

CAR was blunted during the menses, suggesting that cortisol might play a phase-specific role in the regulation of the cycle. Additionally, premenstrual symptoms, including pain, were more severe when ovarian steroid levels reduced (i.e., menses and the premenstrual phase).

Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences, and Countermeasures

Circadian (∼24-hour) timing systems pervade all kingdoms of life and temporally optimize behavior and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behavior and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these, too, are increasingly subject to disruption. A large proportion of the world's population is at increased risk of environmentally driven circadian rhythm and sleep disruption, and a minority of individuals are also genetically predisposed to circadian misalignment and sleep disorders. The consequences of disruption to the circadian system and sleep are profound and include myriad metabolic ramifications, some of which may be compounded by adverse effects on dietary choices. If not addressed, the deleterious effects of such disruption will continue to cause widespread health problems; therefore, implementation of the numerous behavioral and pharmaceutical interventions that can help restore circadian system alignment and enhance sleep will be important.

Gender, Headaches, and Sleep Health in High School Students

BACKGROUND

The effects of gender, headaches, and their interaction on sleep health (sleep duration, sleep onset and continuity, and indications of hypersomnolence) have not been well studied.

MATERIALS AND METHODS

For American adolescents, we contrasted sleep health variables between males (n = 378) and females (n = 372) and between individuals with chronic headaches (n = 102 females and 60 males) and without chronic headaches (n = 270 females and 318 males) using data from surveys.

RESULTS

Not all measures of sleep health differed between groups, but the following patterns were observed for the measures that did differ. Females reported shorter sleep durations on school nights (p = 0.001), increased likelihood of sleepiness on school days (p < 0.05), and higher hypersomnolence scores compared with males (p = 0.005). Individuals with headaches reported shorter sleep durations on weekends (p = 0.009) and higher hypersomnolence scores (p = 0.009) than individuals without headaches. Interestingly, females with headaches reported worse sleep health than females without headaches for multiple measures. Males with headaches did not differ from males without headaches, except for greater waking at night (p = 0.04).

CONCLUSIONS

These results are consistent with other studies of gender-based differences in sleep health and emphasize the importance of recognizing the risk of headache in female adolescents and treating that condition to prevent additional sleep health issues.

Variation in maternal urinary cortisol profiles across the peri-conceptional period: a longitudinal description and evaluation of potential functions

STUDY QUESTION

How do women's first morning urinary cortisol levels, a marker of stress axis activity, vary during the peri-conceptional period (the 12 weeks around conception)?

SUMMARY ANSWER

First morning urinary cortisol follows an overall increasing trajectory across the peri-conceptional period, interrupted by 2 week-long decreases during the week preceding conception and the fifth week following conception.

WHAT IS KNOWN ALREADY

Later gestational stages (i.e. second and third trimesters) are characterized by increasing levels of circulating cortisol. This increase is hypothesized to constitute a response to the energy demands imposed by fetal growth, and the development of energy reserves in preparation for nursing and performing regular activities while carrying pregnancy's extra weight and volume.

STUDY DESIGN, SIZE, DURATION

This study is based on a data set collected as part of a longitudinal, naturalistic investigation into the interactions between the stress (hypothalamic-pituitary-adrenal axis (HPAA)) and reproductive (hypothalamic-pituitary-gonadal axis (HPGA)) axes. Biomarkers of HPAA and HPGA function were quantified in first morning urinary specimens collected every other day from 22 healthy women who conceived a pregnancy during the study. We analyzed the longitudinal within- and between-individual variation in first morning urinary cortisol levels across the 12-week peri-conceptional period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were recruited from two rural, aboriginal, neighboring communities in Guatemala. Cortisol, estradiol and progesterone metabolites (estrone-3-glucuronide and pregnanediol glucuronide, respectively) and hCG levels were quantified in first morning urinary specimens using immunoassays to determine time of conception and confirm pregnancy maintenance. Linear mixed-effects models with regression splines were used to evaluate the magnitude and significance of changes in cortisol trajectories.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, maternal first morning urinary cortisol increased from 6 weeks prior to conception (geometric mean ± SD = 58.14 ± 36.00 ng/ml) to 6 weeks post-conception (89.29 ± 46.76 ng/ml). The magnitude of the increase between the pre- and post-conception periods varied significantly between women (likelihood ratio test statistic = 8.0017, P = 0.005). The peri-conceptional period is characterized by an increasing cortisol trajectory (+1.36% per day; P = 0.007) interrupted by a week-long decline immediately prior to conception (-4.02% per day; P = 0.0013). After conception cortisol increased again (+1.73% per day; P = 0.0008) for 4 weeks, fell in the fifth week (-6.60% per day; P = 0.0002) and increased again in post-conceptional week 6 (+8.86% per day; P = 0.002). Maternal urinary cortisol levels varied with sex of the gestating embryo. During gestational week 2, mothers carrying female embryos (N = 10) had higher mean cortisol levels than those carrying male embryos (N = 9) (t(17) = 2.28, P = 0.04).

LIMITATIONS, REASONS FOR CAUTION

Our results are based on a relatively small sample (n = 22) of women. However, our repeated-measures design with an average of 27 ± 8 (mean ± SD) data points per woman strengthens the precision of estimates resulting in high statistical power. Additionally, our study population's high degree of ethnic and cultural homogeneity reduces the effects of confounders compared with those found in industrialized populations. This higher level of homogeneity also increases our statistical power. However, since there may be small differences in absolute cortisol values among ethnic groups, the social and biological background of our sample may affect the generalizability of our results. General patterns of HPAA activity, however, are expected to be universal across women. Finally, as there is, to the best of our knowledge, no evidence to the contrary, we assumed that urinary cortisol levels reflect HPAA activity and that changes in gonadal steroids across the menstrual cycle do not affect the levels of free cortisol measured in urine.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this is the first longitudinal profile of basal maternal HPAA activity across the peri-conceptional period. A basic understanding of the normative (basal as opposed to stress-induced) changes in HPAA activity across this period is needed to accurately assess women's stress at this juncture. Importantly, changes in HPAA activity are likely to play a critical role in ovulation, fertilization, implantation, placentation and embryonic programing. Thus, this novel information should aid in the development of interventions aimed at preventing or moderating undesired effects of maternal physiological stress during the peri-conceptional period on reproductive outcomes as well as embryonic development.

STUDY FUNDING/COMPETING INTERESTS

This research was funded by a CIHR IGH Open Operating grant (CIHR 106705) to P.A.N. and L.Z.; a Simon Fraser University (SFU) President's Start-up grant, a Community Trust Endowment Fund grant through SFU's Human Evolutionary Studies Program and a Michael Smith Foundation for Health Research Career Investigator Scholar Award to P.A.N.; an NSERC Discovery grant to L.Z.; a CIHR Post-Doctoral Fellowship to C.K.B. and an NSERC Undergraduate Student Research Award to H.M. and J.C.B. The funding agencies had no role in the design, analysis, interpretation or reporting of the findings. There are no competing interests.

TRIAL REGISTRATION NUMBER

Not applicable.

Determinants of shortened, disrupted, and mistimed sleep and associated metabolic health consequences in healthy humans

Recent increases in the prevalence of obesity and type 2 diabetes mellitus (T2DM) in modern societies have been paralleled by reductions in the time their denizens spend asleep. Epidemiological studies have shown that disturbed sleep-comprising short, low-quality, and mistimed sleep-increases the risk of metabolic diseases, especially obesity and T2DM. Supporting a causal role of disturbed sleep, experimental animal and human studies have found that sleep loss can impair metabolic control and body weight regulation. Possible mechanisms for the observed changes comprise sleep loss-induced changes in appetite-signaling hormones (e.g., higher levels of the hunger-promoting hormone ghrelin) or hedonic brain responses, altered responses of peripheral tissues to metabolic signals, and changes in energy intake and expenditure. Even though the overall consensus is that sleep loss leads to metabolic perturbations promoting the development of obesity and T2DM, experimental evidence supporting the validity of this view has been inconsistent. This Perspective aims at discussing molecular to behavioral factors through which short, low-quality, and mistimed sleep may threaten metabolic public health. In this context, possible factors that may determine the extent to which poor sleep patterns increase the risk of metabolic pathologies within and across generations will be discussed (e.g., timing and genetics).

Associations between sleep parameters and food reward

This study examined the effects of acute, isocaloric aerobic and resistance exercise on different sleep parameters, and whether changes in these sleep parameters between sessions were related to next morning food reward. Fourteen men and women (age: 21.9 ± 2.7 years; body mass index: 22.7 ± 1.9 kg m(-) ²) participated in three randomized crossover sessions: aerobic exercise; resistance exercise; and sedentary control. Target exercise energy expenditure was matched at 4 kcal kg(-1) of body weight, and performed at 70% of VO2peak or 70% of 1 repetition-maximal. Sleep was measured (accelerometry) for 22 h following each session. The 'wanting' for visual food cues (validated computer task) was assessed the next morning. There were no differences in sleep parameters and food 'wanting' between conditions. Decreases in sleep duration and earlier wake-times were significantly associated with increased food 'wanting' between sessions (P = 0.001). However, these associations were no longer significant after controlling for elapsed time between wake-time and the food reward task. These findings suggest that shorter sleep durations and earlier wake-times are associated with increased food reward, but these associations are driven by elapsed time between awakening and completion of the food reward task.