REM sleep characteristics of nightmare sufferers before and after REM sleep deprivation.

OBJECTIVES: To examine whether disrupted regulation of REM sleep propensity is implicated in nightmare (NM) pathophysiology. BACKGROUND: Heightened REM propensity induced by REM sleep deprivation is belied by increases in REM %, REM density and the dream-like quality of dream mentation during post-deprivation recovery sleep. Compromised regulation of REM sleep propensity may be a contributing factor in the pathophysiology of frequent NMs. METHODS: A preliminary study of 14 subjects with frequent NMs (> or = 1 NM/week; 27.6+/-9.9 years) and 11 healthy control subjects (<1 NM/month; 24.3+/-5.3 years) was undertaken. Subjects completed home sleep/dream logs and underwent three nights of polysomnographic recording with REM sleep deprivation on night 2. Group differences were assessed for a battery of REM sleep and dream measures on nights 1 and 3. RESULTS: Several measures, including #skipped early-night REM periods, REM latency, REM/NREM cycle length, early/late REM density, REM rebound, late-night REM% and dream vividness, suggested that REM sleep propensity was abnormally low for the frequent NM group throughout the 3-day study. CONCLUSIONS: Findings raise the possibility that REM anomalies recorded from NM sufferers sleeping in the laboratory environment reflect a disruption of one or more endogenous regulators of REM sleep propensity.

Overnight emotional adaptation to negative stimuli is altered by REM sleep deprivation and is correlated with intervening dream emotions.

Rapid eye movement (REM) sleep and dreaming may be implicated in cross-night adaptation to emotionally negative events. To evaluate the impact of REM sleep deprivation (REMD) and the presence of dream emotions on a possible emotional adaptation (EA) function, 35 healthy subjects randomly assigned to REMD (n = 17; mean age 26.4 +/- 4.3 years) and control (n = 18; mean age 23.7 +/- 4.4 years) groups underwent a partial REMD and control nights in the laboratory, respectively. In the evening preceding and morning following REMD, subjects rated neutral and negative pictures on scales of valence and arousal and EA scores were calculated. Subjects also rated dream emotions using the same scales and a 10-item emotions list. REMD was relatively successful in decreasing REM% on the experimental night, although a mean split procedure was applied to better differentiate subjects high and low in REM%. High and low groups differed - but in a direction contrary to expectations. Subjects high in REMD% showed greater adaptation to negative pictures on arousal ratings than did those low in REMD% (P < 0.05), even after statistically controlling sleep efficiency and awakening times. Subjects above the median on EA(valence) had less intense overall dream negativity (P < 0.005) and dream sadness (P < 0.004) than subjects below the median. A correlation between the emotional intensities of the morning dream and the morning picture ratings supports a possible emotional carry-over effect. REM sleep may enhance morning reactivity to negative emotional stimuli. Further, REM sleep and dreaming may be implicated in different dimensions of cross-night adaptation to negative emotions.

Longitudinal study of preschool sleep disturbance: the predictive role of maladaptive parental behaviors, early sleep problems, and child/mother psychological factors.

OBJECTIVE: To determine if maladaptive parental behaviors (at age 29-41 months) and mother/child psychological characteristics predict future sleep disturbances in 50-month-old to 6-year-old preschoolers, while controlling for early (age 5-17 months) sleep and sociodemographic factors. DESIGN: Randomized survey; children assessed annually from 5 months to 6 years of age. SETTING: Participants' homes. PARTICIPANTS: Representative sample of 987 children born in the province of Quebec, Canada, in 1997-1998. MAIN OUTCOME MEASURES: Questionnaires and interview, including responses from 7 points for 3 key dependent measures: bad dreams (BD), total sleep time (TST) less than 10 hours/night, and sleep-onset latency (SOL) of 15 minutes or more. RESULTS: Early (age 5-17 months) sleep disturbances predicted maladaptive parental behaviors (eg, mother present at sleep onset, giving food/drink after child awakens) at ages 29 and 41 months. Some parental behaviors in turn predicted future BD, TST less than 10 hours/night, and SOL of 15 minutes or more. However, most relationships did not remain significant in adjusted models that controlled for early sleep problems. Bad dreams were predicted by psychological variables (child's anxiety, mother's feeling of efficacy), as was TST (child's difficult temperament and anxiety, mother's depressive symptoms). However, SOL of 15 minutes or more was predicted by several parental behaviors even in adjusted models; cosleeping after awakenings was a risk factor while mother's presence at sleep onset was a protective factor. CONCLUSIONS: Findings support the hypothesis that maladaptive parental behaviors develop in reaction to preexisting sleep difficulties. Further, early sleep difficulties are more predictive than parental behaviors in explaining BD and foreshortened TST beginning at age 50 months. Results are interpreted in light of early emotive/physiological self-regulation problems.

Longitudinal study of bad dreams in preschool-aged children: prevalence, demographic correlates, risk and protective factors.

STUDY OBJECTIVES: To (1) clarify the epidemiology of bad dreams in children and investigate risk and protective factors related to (2) the child's sleep, (3) parental sleep-enabling practices, and (4) the child's temperament. DESIGN: Longitudinal with 6 time points from 5 months to 6 years. SETTING: Subjects' homes. PARTICIPANTS: Representative sample of 987 children in the Province of Quebec. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Longitudinal logistic regression analysis models with primary endpoints of presence or absence of parent-rated bad dreams at 29 months, 41 months, 50 months, 5 years, and 6 years and predictor variables of demographic characteristics, parent ratings of child's sleep characteristics, parental sleep-enabling practices (e.g., cosleeping), and child's psychological characteristics at 5 and 17 months (anxiousness, temperament). Mothers' ratings indicated lower than expected prevalence of frequent bad dreams (1.3% to 3.9%). Demographic correlates of bad dreams were high family income, absence of siblings at 29 months, and a non-immigrant mother. The best predictor at 41 and 50 months was the presence of bad dreams the preceding year, whereas at 5 and 6 years, it was their earlier presence at 29 months. Early protective factors were parental practices favoring emotional nurturance after night awakenings (29 and 41 months); early risk factors were sleep-onset emotional nurturance (29 months), difficult temperament (5 months), and anxiousness (17 months). CONCLUSIONS: Bad dreams in preschoolers are less prevalent than thought but, when present, are trait-like in nature and associated with personality characteristics measured as early as 5 months. A stress-diathesis model may best account for the observed pattern of predictive factors.

Disturbed dreaming, posttraumatic stress disorder, and affect distress: a review and neurocognitive model.

Nightmares are common, occurring weekly in 4%-10% of the population, and are associated with female gender, younger age, increased stress, psychopathology, and dispositional traits. Nightmare pathogenesis remains unexplained, as do differences between nontraumatic and posttraumatic nightmares (for those with or without posttraumatic stress disorder) and relations with waking functioning. No models adequately explain nightmares nor have they been reconciled with recent developments in cognitive neuroscience, fear acquisition, and emotional memory. The authors review the recent literature and propose a conceptual framework for understanding a spectrum of dysphoric dreaming. Central to this is the notion that variations in nightmare prevalence, frequency, severity, and psychopathological comorbidity reflect the influence of both affect load, a consequence of daily variations in emotional pressure, and affect distress, a disposition to experience events with distressing, highly reactive emotions. In a cross-state, multilevel model of dream function and nightmare production, the authors integrate findings on emotional memory structures and the brain correlates of emotion.

What are the memory sources of dreaming?

Investigators since Freud have appreciated that memories of the people, places, activities and emotions of daily life are reflected in dreams but are typically so fragmented that their predictability is nil. The mechanisms that translate such memories into dream images remain largely unknown. New research targeting relationships between dreaming, memory and the hippocampus is producing a new theory to explain how, why and when we dream of waking life events.

Immediate and delayed incorporations of events into dreams: further replication and implications for dream function.

The incorporation of memories into dreams is characterized by two types of temporal effects: the day-residue effect, involving immediate incorporations of events from the preceding day, and the dream-lag effect, involving incorporations delayed by about a week. This study was designed to replicate these two effects while controlling several prior methodological problems and to provide preliminary information about potential functions of delayed event incorporations. Introductory Psychology students were asked to recall dreams at home for 1 week. Subsequently, they were instructed to select a single dream and to retrieve past events related to it that arose from one of seven randomly determined days prior to the dream (days 1-7). They then rated both their confidence in recall of events and the extent of correspondence between events and dreams. Judges evaluated qualities of the reported events using scales derived from theories about the function of delayed incorporations. Average ratings of correspondences between dreams and events were high for predream days 1 and 2, low for days 3 and 4 and high again for days 5-7, but only for participants who rated their confidence in recall of events as high and only for females. Delayed incorporations were more likely than immediate incorporations to refer to events characterized by interpersonal interactions, spatial locations, resolved problems and positive emotions. The findings are consistent with the possibility that processes with circaseptan (about 7 days) morphology underlie dream incorporation and that these processes subserve the functions of socio-emotional adaptation and memory consolidation.

Chronobiological features of dream production.

A review of the scientific literature clarifies several chronobiological features of dreaming. The literature supports the conclusions that dreaming 'intensity' and, to a lesser extent dream-like quality, is modulated by (1) a sinusoidal, 90-min ultradian oscillation, (2) a 'switch-like' circadian oscillation, (3) a 12-h circasemidian rhythm, and (4) a 28-day circatrigintan rhythm (for women). Further, access to dream memory sources appears to be modulated by (5) a 7-day circaseptan rhythm. Further study of these rhythmic influences on dreaming may help to explain diverse and often contradictory findings in the dream research literature, to clarify relationships between dreaming and waking cognitive processes, to explain relationships between disturbed phase relationships and dream disturbances and to shed new light on the problems of dreaming's functions and biological markers. Further chronobiological studies of dreaming will likely enable the development of theoretical models that explain how interactions between and within major levels of oscillation determine the variable characteristics of dreaming.

Reduced Alpha power associated with the recall of mentation from Stage 2 and Stage REM sleep.

Relationships between Alpha (8-12 Hz) activity and cognitive processes during wakefulness raise the possibility of similar relationships between Alpha and cognitive activity during sleep. We hypothesized that Alpha power decreases during both Stage 2 and REM sleep would index the presence of sleep mentation in these stages. Absolute power for six classical EEG bands and three Alpha subbands was calculated for Stage 2 and REM sleep awakenings both with and without mentation recall. In both stages, recall was associated with lower Alpha power, especially with middle Alpha power (9.5-11.5 Hz). Unexpectedly, a similar effect for Delta power (0.5-4.0 Hz) was also observed. The Alpha effect may reflect cognitive elaboration active in the minutes preceding awakening; however, attention and memory processes cannot be excluded. The Delta effect is consistent with prior observations of regular linkages between Alpha and Delta power during sleep.

Sleep pathophysiology in posttraumatic stress disorder and idiopathic nightmare sufferers.

BACKGROUND: Nightmares are common in posttraumatic stress disorder (PTSD), but they also frequently occur in idiopathic form. Findings associated with sleep disturbances in these two groups have been inconsistent, and sparse for idiopathic nightmares. The aim of the present study was to investigate whether sleep anomalies in PTSD sufferers with frequent nightmares (P-NM) differ from those observed in non-PTSD, idiopathic nightmare (I-NM) sufferers and healthy individuals. METHODS: Sleep measures were obtained from nine P-NM sufferers, 11 I-NM sufferers, and 13 healthy control subjects. All participants slept in the laboratory for two consecutive nights where electroencephalogram, electro-oculogram, chin and leg electromyogram, electrocardiogram, and respiration were recorded continuously. RESULTS: Posttraumatic nightmare sufferers had significantly more nocturnal awakenings than did I-NM sufferers and control subjects. Elevated indices of periodic leg movements (PLMs) during rapid eye movement (REM) and non-REM sleep characterized both P-NM and I-NM sufferers. CONCLUSIONS: Posttraumatic nightmare sufferers exhibit more nocturnal awakenings than do I-NM sufferers and control subjects, which supports the hypothesis of hyperarousal in sleep in PTSD sufferers; however, elevated PLM indices in both P-NM and I-NM sufferers suggest that PLMs may not be a marker of hyperarousal in sleep of PTSD sufferers. Rather, PLMs may be a correlate of processes contributing to intense negative dreaming.

Incorporation of pain in dreams of hospitalized burn victims.

It has been shown that realistic, localized painful sensations can be experienced in dreams either through direct incorporation or from past memories of pain. Nevertheless, the frequency of pain dreams in healthy subjects is low. This prospective study was designed to evaluate the occurrence and frequency of pain in the dreams of patients suffering from burn pain. Twenty-eight nonventilated burn victims were interviewed for 5 consecutive mornings during the first week of hospitalization. A structured-interview protocol was used to collect information on dream content, quality of sleep, and pain intensity and location. Patients were also administered the Impact of Event Scale to assess posttraumatic symptoms. Thirty-nine percent of patients reported 19 pain dreams on a total of 63 dreams (30%). Patients with pain dreams showed evidence of worse sleep, more nightmares, higher intake of anxiolytic medication, and higher scores on the Impact of Event Scale than did patents reporting dreams with no pain content. Moreover, patients with pain dreams also had a tendency to report more intense pain during therapeutic procedures. Although more than half of our sample did not report pain dreams, these results suggest that pain dreams do occur at a greater frequency in suffering populations than in normal volunteers. More importantly, dreaming about pain may be an added stress for burn patents and may contribute to both poor sleep and higher pain intensity, which could evolve into a cycle of pain-anxiety-sleeplessness.

Quality of sleep and its daily relationship to pain intensity in hospitalized adult burn patients.

Sleep disturbances are frequently reported in victims following burn injuries. This prospective study was designed to assess sleep quality and to examine its daily relationship to pain intensity within the first week of hospitalization. Twenty-eight non-ventilated patients were interviewed during 5 consecutive mornings (number of observations=140) to collect information about perceived quality of sleep (visual analogue scale, number of hours, number of awakenings, presence of nightmares). Pain intensity was assessed at rest (nighttime, morning, during the day) and following therapeutic procedures using a 0-10 numeric scale. Seventy-five percent of patients reported sleep disturbances at some point during the study although, in most patients, sleep quality was not consistently poor. Pooled cross-section regression analyses showed significant temporal relationships between quality of sleep and pain intensity such that a night of poor sleep was followed by a significantly more painful day. Pain during the day was not found to be a significant predictor of poor sleep on the following night. These results support previous findings that perceived quality of sleep following burn injury is poor. Moreover, they show a daily relationship between quality of sleep and acute burn pain in which poor sleep is linked to higher pain intensity during the day.