A 2022 Survey of Commercially Available Smartphone Apps for Sleep: Most Enhance Sleep.

Commercially available smartphone apps represent an ever-evolving and fast-growing market. Our review systematically surveyed currently available commercial sleep smartphone apps to provide details to inform both providers and patients alike, in addition to the healthy consumer market. Most current sleep apps offer a free version and are designed to be used while awake, prior to sleep, and focus on the enhancement of sleep, rather than measurement, by targeting sleep latency using auditory stimuli. Sleep apps could be considered a possible strategy for patients and consumers to improve their sleep, although further validation of specific apps is recommended.

Sleep duration prior to an enterotoxigenic Escherichia coli challenge predicts diarrhea severity during infection.

BACKGROUND: Acute diarrhea is the most frequent diagnosis among ill travelers. Sleep loss may weaken the body's defense against pathogens and increase susceptibility to infection. The relationship between sleep and infectious diarrhea has not been studied and was assessed utilizing data from a controlled human infection model (CHIM) for enterotoxigenic Escherichia coli (ETEC). METHODS: During a CHIM assessing the efficacy of an immunoprophylactic targeting ETEC against moderate-to-severe diarrhea (MSD) following challenge, we measured sleep via actigraphy over an 8-day inpatient period. We hypothesized better sleep pre-challenge would predict illness symptomatology following challenge. RESULTS: Among 57 participants (aged 34.4 ± 8.1 years, 64% male), there was no relationship between sleep metrics and incidence of MSD. However, longer total sleep time the night preceding ETEC challenge was associated with lower maximum 24 h diarrhea volume (B = -1.80, p = 0.01) and total diarrhea volume (B = -2.45, p = 0.01). CONCLUSIONS: This novel study showed that shorter sleep duration predicted diarrhea severity over the course of an ETEC infection. Future work should experimentally manipulate sleep to further clarify its impact on diarrhea-related outcomes for ETEC and other important enteric pathogens.

Sleep loss suicidal ideation: the role of trait extraversion.

Background: It is known that sleep disturbance is associated with increased suicidal thinking. Moreover, completed suicides, when adjusted for the proportion of the populace that is awake at a given time, are more probable during the late night/early morning hours. Despite these concerns, no studies have examined the role of trait-like individual differences in vulnerability to suicidal ideation during sleep deprivation or insomnia. In two separate studies, we examined whether the trait of extraversion is predictive of changes in suicidal thinking following two nights of sleep deprivation and among individuals meeting the criteria for insomnia. Methods: Study 1: Twenty-five healthy military personnel (20 males), ages 20-35 completed the NEO-PI-R Extraversion scale and the Suicidal Ideation (SUI) scale of the Personality Assessment Inventory (PAI). Participants completed 77 h of continuous sleep deprivation. After 56 h of sleep deprivation, participants completed the SUI scale a second time. We predicted a change in SUI scores from baseline extraversion. Study 2: 2,061 adults aged 18-79 (900 males) were divided into two groups based on the clinical threshold (≥ 10) on the Insomnia Severity Index (ISI) and completed measures of extraversion and depression, including the suicide item of the Patient Health Questionnaire-9 (PHQ9). Results: Study 1: After controlling for the caffeine group and changes in PAI Depression, Extraversion scores were used to predict changes in SUI scores using stepwise multiple linear regression. Higher Extraversion was significantly associated with increased non-clinical suicidal ideation following sleep loss, ß = 0.463, partial r = 0.512, p = 0.013. Study 2: After controlling for depression, the effect of insomnia on suicidal ideation was moderated by trait extraversion (p < 0.0001). Overall, the presence or absence of insomnia had little effect on individuals low in trait extraversion (i.e., introverts), but insomnia was associated with significantly higher suicidal ideation among high trait extraverted individuals. Conclusions: Higher trait extraversion was associated with increased vulnerability to suicidal ideation between rested baseline and total sleep deprivation and was associated with greater suicidal ideation among those meeting criteria for clinically severe insomnia. These findings point to a potential trait-like vulnerability factor that may further our understanding of sleep disruption in the phenomenology of suicide.

Sleep extension reduces fatigue in healthy, normally-sleeping young adults.

OBJECTIVE: To assess the effects of one week of sleep extension on mood, fatigue and subjective sleepiness in normal-sleeping young adults. METHODS: Twenty-seven adults (age 24.4±5.4 years, 11 female) participated. At-home baseline sleep/wake patterns were recorded with wrist actigraphy for 14 days. This was followed by two nights of in-lab baseline sleep with 8 hours time in bed (TIB), then 7 nights with TIB extended to 10 hours (2100-0700 hours). Fatigue, mood, and sleepiness were assessed following the 2nd and 9th nights of in-laboratory sleep (i.e., 2 nights with 8hTIB and 7 nights with 10 hours TIB, respectively) using the Automated Neuropsychological Assessment Metric and Karolinska Sleepiness Scale. Paired t-tests were used to compare mood, fatigue, and sleepiness ratings between conditions. RESULTS: At-home wrist actigraphy revealed a mean nightly total sleep time (TST) of 7.53 +/- 0.88 hours of sleep per night. Mean in-lab baseline sleep duration (7.76 +/- 0.59) did not differ from at-home sleep. However, during sleep extension, mean TST was 9.36 +/- 0.37 hours per night, significantly more than during the in-lab baseline (p < .001). Following sleep extension, fatigue ratings were significantly reduced, relative to baseline (p = .03). However, sleep extension had no other significant effects on subjective ratings of mood or sleepiness. CONCLUSIONS: Sleep extension resulted in reduced fatigue in healthy, normal-sleeping young adults, although subjective sleepiness and mood were not improved. Implications include the possibility that (a) the effects of sleep extension on various aspects of mood depend upon the extent to which those aspects of mood are made salient by the study design and methodology; and (b) sleep extension may prove beneficial to fatigue-related conditions such as "burnout."

Limited Efficacy of Caffeine and Recovery Costs During and Following 5 Days of Chronic Sleep Restriction.

Objectives: To investigate the effects of caffeine on psychomotor vigilance and sleepiness during sleep restriction and following subsequent recovery sleep. Methods: Participants were N = 48 healthy good sleepers. All participants underwent five nights of sleep satiation (time-in-bed [TIB]: 10 hours), followed by five nights of sleep restriction (TIB: 5 hours), and three nights of recovery sleep (TIB: 8 hours) in a sleep laboratory. Caffeine (200 mg) or placebo was administered in the form of chewing gum at 08:00 am and 12:00 pm each day during the sleep restriction phase. Participants completed hourly 10-minute psychomotor vigilance tests and a modified Maintenance of Wakefulness Test approximately every 4 hours during the sleep restriction and recovery phases. Results: Caffeine maintained objective alertness compared to placebo across the first 3 days of sleep restriction, but this effect was no longer evident by the fourth day. A similar pattern of results was found for Maintenance of Wakefulness Test sleep latencies, such that those in the caffeine group (compared to placebo) did not show maintenance of wakefulness relative to baseline after the second night of restriction. Compared to placebo, participants in the caffeine condition displayed slower return to baseline in alertness and wakefulness across the recovery sleep period. Finally, the caffeine group showed greater N3 sleep duration during recovery. Conclusions: Caffeine appears to have limited efficacy for maintaining alertness and wakefulness across 5 days of sleep restriction. Perhaps more importantly, there may be recovery costs associated with caffeine use following conditions of prolonged sleep loss.