Evidence for a relationship between chronotype and reproductive function in women

There is evidence for the reciprocal interaction between circadian oscillation and reproduction, and disruption of circadian rhythms has been associated with impaired menstrual functions and reduced fertility in women. However, only little information is available on the relationship between reproduction and chronotype. The aim of the present study is to better assess this relationship. The participants (aged 25 to 74?yrs) were selected randomly from the Finnish Population Information System. The data from 2672 female participants of the National FINRISK Survey 2007 were analyzed to test the associations between chronotype (morning, intermediate, or evening) and reproductive features. Of the participants, 139 (5.6%) were evening, 1217 (48.7%) intermediate, and 1145 (45.8%) morning chronotypes. Among the participants aged 25 to 54?yrs, the duration of menstrual cycle was longer among evening chronotypes (28.8?±?4.4?d) than among morning (27.7?±?2.6?d; p?<?0.01) and intermediate (27.8?±?3.3?d; p?=?0.05) chronotypes. Significant correlations were found between the higher morningness-eveningness scores (the more of morning chronotype) and the shorter durations of menstrual bleeding, both in the whole sample (p?<?0.001) and after limiting the analyses to women younger than 55?yrs (p?<?0.05). In multivariable analyses on the whole sample, as compared with morning chronotypes, intermediate chronotypes had a significantly longer duration of menstrual bleeding (B?=?0.160, 95% confidence interval [CI]?=?0.044 to 0.276; p?<?0.01) as well as a higher odds for difficulties in getting pregnant (odds ratio [OR]?=?1.464, 95% CI?=?1.118 to 1.917; p?<?0.01). Our findings suggest that chronotype is related to the reproductive function in women.     

Chronotype,bed timing and total sleep time in seniors

Many older adults (seniors) experience problems with getting enough sleep. Because of the link between sleep and circadian rhythms, changes in bedtime lead to changes in the amount of sleep obtained. Although primarily determined genetically, chronotype changes with advancing age towards a more morning-type (M-type) orientation. In a 2006 study, we have found a linear relationship, by which the earlier a senior’s bedtime, the more sleep she/he will obtain. The aim of this study was to see whether this relationship differs for M-type seniors, as compared to seniors outside the M-type category. Retired seniors (n?=?954, 535?M, 410F, 65?years+, mean age 74.4?years) taking part in a telephone interview were divided into M-types and Other types (O-types) using the Composite Scale of Morningness (CSM). The relationship between bedtime and Total Sleep Time (TST), and between rise-time and TST, was tested using linear regression separately for M-types and O-types. For each participant, habitual bedtime, rise-time and total Sleep Time (TST) [after removing time spent in unwanted wakefulness] were obtained using a telephone version of the Sleep Timing Questionnaire (STQ). Both chronotype groups showed a significant linear relationship between bedtime and TST (p?<?0.001); with earlier bedtimes leading to more TST (M-type 5.6?min; O-type 4.4?min per 10?min change [slope difference p?=?0.05]); and an opposite relationship between rise-time and TST with earlier rise-times leading to less TST (M-type 6.7?min; O-type 4.2?min per 10?min change [slope difference p?=?0.001]). M-types retired to bed 56?min earlier (p?<?0.001), awoke 93?min earlier (p?<?0.001) and obtained 23?min less TST (p?<?0.001) than O-types. In conclusion, both chronotypes showed TST to be related in a linear way to bedtime and rise-time; the overall shorter TST in M-types was due to them rising 93?min earlier, but only retiring to bed 56?min earlier than O-types; as well as having a steeper rise-time versus TST relationship.     

Validity of the Japanese version of the Munich ChronoType Questionnaire

To assess circadian preference with a score, the Morningness-Eveningness Questionnaire (MEQ) has been used for more than 3 decades now. More recently, the Munich ChronoType Questionnaire (MCTQ) was developed: it asks for sleep-wake behavior on work and free days and uses the midpoint of sleep on free days (MSF), corrected for sleep debt accumulated during the work week as an indicator of chronotype (MSF_sc). In this study, we developed a Japanese version of the MCTQ by using a translation/back-translation approach including an examination of its semantic validity. In a subsequent questionnaire survey, 450 adult men and women completed the Japanese versions of the MCTQ and MEQ. Results showed that MEQ scores were significantly negatively correlated with mid-sleep parameters assessed by the MCTQ, on both, work and free days, as well as with the chronotype measure MSF_sc (r?=??0.580 to ?0.652, all p?<?0.001). As in the original German version, the strongest correlation was observed between MEQ score and MSF. A physiological validation study using dim light melatonin onset as a circadian phase marker (N?=?37) showed a high correlation between chronotype as assessed with the MSF_sc (r?=?0.542, p?<?0.001), and less so for MEQ score (r?=??0.402, p?=?0.055). These results demonstrate the validity of the Japanese MCTQ and provide further support of the adequacy of the MCTQ as a chronotype measure.     

Influence of acoustic stimulation on the circadian and ultradian rhythm of premature infants

The aim of the present study was to evaluate the development of the circadian rhythm of the salivary cortisol in premature infants and its correlation with the onset of the sleep–activity behavior pattern during the first 3 weeks of life under controlled light:dark conditions. Furthermore, we investigated the influence of acoustic stimulation by audiotaped lullabies or the maternal voice on the cortisol values and long-term sleep–activity patterns. The study was a block-randomized, prospective clinical trial with a study population of 62 preterm neonates (30?<?37 gestational age). We compared two study groups who listened either to music or to the maternal voice (music: N?=?20; maternal voice: N?=?20) with a matched control group (N?=?22). The acoustic stimulation took place every evening between 20:00 and 21:00?h for 30?min over a period of 2 weeks. The cortisol values and activity–rest behavior of the neonates were determined during the first 3 weeks of life on the 1st, 7th and 14th day. Actigraphic monitoring was used to record the activity pattern continuously over 24?h and a validated algorithm for neonates was used to estimate sleep and wakefulness. The saliva samples were obtained 10?min before and 10?min after the acoustic interventions for the study groups. Additionally, saliva samples were obtained from the control group seven times over a 24-h period (20:00, 21:00, 01:00, 05:00, 08:00, 13:00 and 17:00?h). The cortisol data were analyzed by fast Fourier transformation to assess periodic characteristics and frequencies. Hierarchical linear modeling was further performed for the statistical analysis. Results: The cortisol rhythm analysis indicated a circadian rhythm pattern for only one premature infant, all others of the neonates showed no circadian or ultradian rhythm in cortisol. Cortisol level of the premature neonates was significantly higher during the first day of the study period at night-time (median: 17.1?nmol/L, IQR?=?9.7–24.4?nmol/L) than on days 7 (median: 9.6?nmol/L, IQR?=?4.7–14.6?nmol/L; Tukey-HSD, z?=?4.12, p?<?0.001) and 14 (IQR?=?5.8–13.7?nmol/L; Tukey-HSD, z?=?2.89, p?<?0.05). No significant effect of acoustic stimulation was observed on the cortisol concentration and sleep–wake behavior. The activity–sleep rhythm of preterm neonates was dominated by ultradian rhythm patterns with a prominent period length of 4?h (30.5%). Activity frequencies of neonates were also significantly higher overnight on the first study day (mean: 329?±?185.1?U) than of night seven (mean: 260.2?±?132.4?U; Tukey-HSD, z?=?2.50, p?<?0.05). Quiet-activity patterns increased, whereas high-activity patterns decreased during the observation period. Average sleep time increased significantly during the study time from day 1 to day 7 (Tukey-HSD, z?=?2.51, p?<?0.05). In conclusion, premature infants showed higher cortisol levels – without a circadian rhythmicity – and higher activity frequencies in the first days after birth which may reflect an adaptation process of neonates after birth. Cortisol concentrations and the activity patterns were not influenced by music interventions.     

Associations of chronotype with social jetlag and behavioral problems in preschool children

The timing, duration, and intensity of sleep are determined by the interaction between a sleep-wake-dependent homeostatic process and a sleep-wake-independent, intrinsic, clock-like circadian process. Chronotype represents individual differences in diurnal preferences, which are not only genetically determined but also influenced by social and environmental factors. Thus, the discrepancy between biological and social clocks, so-called “social jetlag”, occurs. Chronotype, social jetlag, and the links between chronotype and behavioral problems are well documented in adults and adolescents. However, such studies on young children are limited. We conducted a survey of sleep and health for preschool children attending kindergarten or childcare centers in Wako, Okayama and Kurashiki cities, Japan, between May and July 2012. A total of 654 children aged 4–6 years (342 boys and 312 girls, with an average age of 4.7 years) were assessed using the Children’s ChronoType Questionnaire and the Strength and Difficulties Questionnaire. Morning (M)-type, neither (N)-type and evening (E)-type accounted for 36.2%, 54.0% and 9.8% of the participants, respectively. The weekday-to-weekend differences in midsleep time – originally proposed as the concept of social jetlag – were 11, 25 and 35?min for M-, N- and E-types, respectively. There was a negative correlation between chronotype and sleep period during weekdays (p?<?0.001) and a positive correlation on weekends (p?<?0.001). The weekday-to-weekend difference in sleep period was 0.5?h for E-types, whereas there was no difference for M-types. Binomial logistic regression analyses were used to examine the links between chronotype and behavioral problems, adjusted for participants’ sex, age, childcare programs and locations. Chronotype was significantly associated with hyperactivity/inattention: N-type (adjusted OR?=?1.74, 95% CI?=?1.03–2.95, p?<?0.05) and E-type (adjusted OR?=?2.47, 95% CI?=?1.18–5.20, p?<?0.05). E-type was significantly associated with conduct problems (adjusted OR?=?2.11, 95% CI?=?1.03–4.31, p?<?0.05) and peer problems (adjusted OR?=?2.75, 95% CI?=?1.18–6.44, p?<?0.05). The results suggest that E-type children are vulnerable to higher social jetlag and more behavioral problems. The immature adjustment function of their endogenous circadian pacemakers may not be able to correct a small but significant social jetlag to synchronize with their social clocks. Furthermore, guidance based on chronobiological evidence is required for parents, teachers and health professionals to help children achieve optimal sleep and reduce behavioral problems.     

SLEEP PATTERNS IN HIGH SCHOOL AND UNIVERSITY STUDENTS: A LONGITUDINAL STUDY

We performed a longitudinal study to investigate whether changes in social zeitgebers and age alter sleep patterns in students during the transition from high school to university. Actimetry was performed on 24 high-school students (mean age?±?SD: 18.4?±?0.9 yrs; 12 females) for two weeks. Recordings were repeated in the same subjects 5 yrs later when they were university students. The sleep period duration and its center, the mid-sleep time, and total sleep time were estimated by actimetry. Actigraphic total sleep time was similar when in high school and at the university on school days (6.31?±?0.47 vs. 6.45?±?0.80?h, p?=?ns) and longer on leisure days by 1.10?±?1.10?h (p?<?0.0001 vs. school days) when in high school, but not at the university. Compared to the high school situation, the mid-sleep time was delayed when at the university on school days (03∶11?±?0.6 vs. 03∶55?±?0.7?h, p?<?0.0001), but not on leisure days. Individual mid-sleep times on school and leisure days when in high school were significantly correlated with the corresponding values 5 yrs later when at the university (r?=?0.58 and r?=?0.55, p?<?0.05, respectively). The large differences in total sleep time between school and leisure days when students attended high school and the delayed mid-sleep time on school days when students attended university are consistent with a circadian phase shift due to changes in class schedules, other zeitgebers, and lifestyle preferences. Age-related changes may also have occurred, although some individuality of the sleep pattern was maintained during the 5 yr study span. These findings have important implications for optimizing school and work schedules in students of different age and level of education. (Author correspondence: pneubloc@usz.uzh.ch)     

Stability and Fragmentation of the Activity Rhythm Across the Sleep-Wake Cycle: The Importance of Age,Lifestyle, and Mental Health

The rhythms of activity across the 24-h sleep-wake cycle, determined in part by the circadian clock, change with aging. Few large-scale studies measured the activity rhythm objectively in the general population. The present population-based study in middle-aged and elderly persons evaluated how activity rhythms change with age, and additionally investigated sociodemographics, mental health, lifestyle, and sleep characteristics as determinants of rhythms of activity. Activity rhythms were measured objectively with actigraphy. Recordings of at least 96?h (138?±?14?h, mean?±?SD) were collected from 1734 people (age: 62?±?9.4?yrs) participating in the Rotterdam Study. Activity rhythms were quantified by calculating interdaily stability, i.e., the stability of the rhythm over days, and intradaily variability, i.e., the fragmentation of the rhythm relative to its 24-h amplitude. We assessed age, gender, presence of a partner, employment, cognitive functioning, depressive symptoms, body mass index (BMI), coffee use, alcohol use, and smoking as determinants. The results indicate that older age is associated with a more stable 24-h activity profile (β?=?0.07, p?=?0.02), but also with a more fragmented distribution of periods of activity and inactivity (β?=?0.20, p?<?0.001). Having more depressive symptoms was related to less stable (β?=??0.07, p?=?0.005) and more fragmented (β?=?0.10, p?<?0.001) rhythms. A high BMI and smoking were also associated with less stable rhythms (BMI: β?=??0.11, p?<?0.001; smoking: β?=??0.11, p?<?0.001) and more fragmented rhythms (BMI: β?=?0.09, p?<?0.001; smoking: β?=?0.11, p?<?0.001). We conclude that with older age the 24-h activity rhythm becomes more rigid, whereas the ability to maintain either an active or inactive state for a longer period of time is compromised. Both characteristics appear to be important for major health issues in old age.     

The impact of training schedules on the sleep and fatigue of elite athletes

In any sport, successful performance requires a planned approach to training and recovery. While sleep is recognized as an essential component of this approach, the amount and quality of sleep routinely obtained by elite athletes has not been systematically evaluated. Data were collected from 70 nationally ranked athletes from seven different sports. Athletes wore wrist activity monitors and completed self-report sleep/training diaries for 2 weeks during normal training. The athletes also recorded their fatigue level prior to each training session using a 7-point scale. On average, the athletes spent 08:18?±?01:12?h in bed, fell asleep at 23:06?±?01:12?h, woke at 6:48?±?01:30?h and obtained 06:30?±?01:24?h of sleep per night. There was a marked difference in the athletes’ sleep/wake behaviour on training days and rest days. Linear mixed model analyses revealed that on nights prior to training days, time spent in bed was significantly shorter (p?=?0.001), sleep onset and offset times were significantly earlier (p?<?0.001) and the amount of sleep obtained was significantly less (p?=?0.001), than on nights prior to rest days. Moreover, there was a significant effect of sleep duration on pre-training fatigue levels (p?≤?0.01). Specifically, shorter sleep durations were associated with higher levels of pre-training fatigue. Taken together, these findings suggest that the amount of sleep an elite athlete obtains is dictated by their training schedule. In particular, early morning starts reduce sleep duration and increase pre-training fatigue levels. When designing schedules, coaches should be aware of the implications of the timing of training sessions for sleep and fatigue. In cases where early morning starts are unavoidable, countermeasures for minimizing sleep loss – such as strategic napping during the day and correct sleep hygiene practices at night – should be considered.     

The difference between in bed and out of bed activity as a behavioral marker of cancer patients: A comparative actigraphic study

The current study was conducted to provide normative data on actigraphic dichotomy index (I?<?O) (the percentage of in bed activity counts that are less than the median of out of bed counts) in healthy population and to assess whether the I?<?O could be an effective index in discriminating the circadian motor activity of cancer patients from healthy controls. In this retrospective study, we recovered 408 actigraphic records from two databases: healthy controls (n?=?182; 79 males; mean age 38.7?±?12.6) and patients with metastatic colorectal cancer (n?=?226; 149 males; mean age 58.4?±?11.4). Beside the usual actigraphic sleep parameters (time in bed, sleep onset latency, total sleep time, wake after sleep onset, sleep efficiency, number of awakenings, and mean motor activity), we also computed the dichotomy index and number of actigraphic wake parameters, namely, diurnal motor activity, diurnal total sleep time, number of sleep episodes, and the mean duration of the longest diurnal sleep episode. Using the Youden index, we calculated the cut off value that performed the best for I?<?O and actigraphic wake parameters. Finally, we created Receiver Operator Characteristic curves to test the efficacy of each actigraphic parameter to discriminate cancer patient from healthy controls. Mean I?<?O was 99.5% (SD, 0.48%) in the healthy group, as compared to 96.6% (SD, 3.6%) in the cancer group (p?<?0.0001). Important age-related effects appeared unlikely after performing both the main analysis with age as a covariate, and a subset analysis in 104 subjects matched for age and sex. In the main analysis, all actigraphic parameters, except total sleep time, significantly differentiated the two groups of participants. However, the I?<?O was the one that clearly performed best. Here, we provide the first large dataset on I?<?O in healthy subjects, we confirm the relevance of this circadian index for discriminating advanced stage colorectal cancer patients from healthy subjects, and we lay the grounds for further investigations of this circadian index in patients with other chronic diseases.     

An observational study on disturbed peripheral circadian rhythms in hemodialysis patients

The quality of life of hemodialysis (HD) patients is hampered by reduced nocturnal sleep quality and excessive daytime sleepiness. In addition to the sleep/wake cycle, levels of circadian biomarkers (e.g. melatonin) are disturbed in end-stage renal disease (ESRD). This suggests impaired circadian clock performance in HD patients, but the underlying mechanism is unknown. In this observational study, diurnal rhythms of sleep, serum melatonin and cortisol concentrations and clock gene mRNA expression are compared between HD patients (n?=?9) and healthy control subjects (n?=?9). In addition, the presence of circulating factors that might affect circadian rhythmicity is tested in vitro with cell culture experiments. Reduced sleep quality (median sleep onset latency [interquartile range] of 23.9 [17.3]?min for patients versus 5.0 [10] minutes for controls, p?<?0.01; mean (± SD) sleep efficiency 70.2?±?8.1% versus 82.9?±?10.9%, p?=?0.02 and mean awake minutes after sleep onset 104.8?±?27.9 versus 54.6?±?41.6 minutes, p?= 0.01) and increased daytime sleepiness (mean Epworth Sleepiness Score of 10.0?±?4.8 versus 3.9?±?2.0, p?<?0.01) were confirmed in HD patients. Reduced nocturnal melatonin concentrations (1 AM: 98.1 [122.9] pmol/L versus 12.5 [44.2] pmol/L, p?= 0.019; 5 AM: 114.0 [131.6] pmol/L versus 11.8 [86.8] pmol/L, p?= 0.031) and affected circadian control of cortisol rhythm and circadian expression of the clock gene REV-ERBα were found. HD patient serum had a higher capacity to synchronize cells in vitro, suggesting an accumulated level of clock resetting compounds in HD patients. These compounds were not cleared by hemodialysis treatment or related to frequently used medications. In conclusion, the abovementioned results strongly suggest a disturbance in circadian timekeeping in peripheral tissues of HD patients. Accumulation of clock resetting compounds possibly contributes to this. Future studies are needed for a better mechanistic understanding of the interaction between renal failure and perturbation of the circadian clock.     

THERMOREGULATORY EFFECT IN HUMANS OF SUPPRESSED ENDOGENOUS MELATONIN BY PRE-SLEEP BRIGHT-LIGHT EXPOSURE IN A COLD ENVIRONMENT

This study investigated the physiological function of suppressed melatonin through thermoregulation in a cold environment. Interactions between thermoregulation directly affected by exposure to a cold environment and indirectly affected by endogenous melatonin suppression by bright-light exposure were examined. Ten male subjects were exposed to two different illumination intensities (30 and 5000 lux) for 4.5?h, and two different ambient temperatures (15 and 27°C) for 2?h before sleep under dark and thermoneutral conditions. Salivary melatonin level was suppressed by bright light (p?<?0.001), although the ambient temperature condition had no significant effect on melatonin. During sleep, significant effects of pre-sleep exposure to a cold ambient temperature (p?<?0.001) and bright light (p?<?0.01) on rectal temperature (T_re) were observed. Pre-sleep, bright-light exposure led to an attenuated fall in T_re during sleep. Moreover, T_re dropped more precipitously after cold exposure than thermoneutral conditions (cold: ?0.54?±?0.07°C/h; thermoneutral: ?0.16?±?0.03°C/h; p?<?0.001). Pre-sleep, bright-light exposure delayed the nadir time of T_re under thermoneutral conditions (p?<?0.05), while cold exposure masked the circadian rhythm with a precipitous decrease in T_re. A significant correlation between the T_re nadir and melatonin level (r?=??0.774, p?<?0.05) indicated that inter-individual differences with higher melatonin levels lead to a reduction in T_re after cold exposure. These results suggest that suppressed endogenous melatonin inhibits the downregulation of the body temperature set-point during sleep. (Author correspondence: ishibasi@design.kyushu-u.ac.jp)     

Wrist actimetry circadian rhythm as a robust predictor of colorectal cancer patients survival

The disruption of the circadian timing system (CTS), which rhythmically controls cellular metabolism and proliferation, accelerated experimental cancer progression. A measure of CTS function in cancer patients could thus provide novel prediction information for outcomes, and help to identify novel specific therapies. The rest-activity circadian rhythm is a reliable and non-invasive CTS biomarker, which was monitored using a wrist watch accelerometer for 2 days in 436 patients with metastatic colorectal cancer. The relative percentage of activity in-bed versus out-of-bed (I?<?O) constituted the tested CTS measure, whose prognostic value for overall survival (OS) and progression-free survival (PFS) was determined in a pooled analysis of three patient cohorts with different treatment exposures. Median OS was 21.6 months [17.8–25.5] for patients with I?<?O above the median value of 97.5% as compared to 11.9 months [10.4–13.3] for those with a lower I?<?O (Log-rank p?<?0.001). Multivariate analyses retained continuous I?<?O as a joint predictor of both OS and PFS, with respective hazard ratios (HR) of 0.954 (p?<?0.001) and 0.970 (p?<?0.001) for each 1% increase in I?<?O. HRs had similar values in all the patient subgroups tested. The circadian physiology biomarker I?<?O constitutes a robust and independent quantitative predictor of cancer patient outcomes, that can be easily and cost-effectively measured during daily living. Interventional studies involving 24-h schedules of clock-targeted drugs, light intensity, exercise and/or meals are needed for testing the relevance of circadian synchronization for the survival of patients with disrupted rhythms.     

Circadian Phase,Sleepiness, and Light Exposure Assessment in Night Workers With and Without Shift Work Disorder

Most night workers are unable to adjust their circadian rhythms to the atypical hours of sleep and wake. Between 10% and 30% of shiftworkers report symptoms of excessive sleepiness and/or insomnia consistent with a diagnosis of shift work disorder (SWD). Difficulties in attaining appropriate shifts in circadian phase, in response to night work, may explain why some individuals develop SWD. In the present study, it was hypothesized that disturbances of sleep and wakefulness in shiftworkers are related to the degree of mismatch between their endogenous circadian rhythms and the night-work schedule of sleep during the day and wake activities at night. Five asymptomatic night workers (ANWs) (3 females; [mean?±?SD] age: 39.2?±?12.5 yrs; mean yrs on shift?=?9.3) and five night workers meeting diagnostic criteria (International Classification of Sleep Disorders [ICSD]-2) for SWD (3 females; age: 35.6?±?8.6 yrs; mean years on shift?=?8.4) participated. All participants were admitted to the sleep center at 16:00?h, where they stayed in a dim light (<10 lux) private room for the study period of 25 consecutive hours. Saliva samples for melatonin assessment were collected at 30-min intervals. Circadian phase was determined from circadian rhythms of salivary melatonin onset (dim light melatonin onset, DLMO) calculated for each individual melatonin profile. Objective sleepiness was assessed using the multiple sleep latency test (MSLT; 13 trials, 2-h intervals starting at 17:00?h). A Mann-Whitney U test was used for evaluation of differences between groups. The DLMO in ANW group was 04:42?±?3.25?h, whereas in the SWD group it was 20:42?±?2.21?h (z = 2.4; p?<?.05). Sleep did not differ between groups, except the SWD group showed an earlier bedtime on off days from work relative to that in ANW group. The MSLT corresponding to night work time (01:00–09:00?h) was significantly shorter (3.6?±?.90?min: [M?±?SEM]) in the SWD group compared with that in ANW group (6.8?±?.93?min). DLMO was significantly correlated with insomnia severity (r = ?.68; p < .03), indicating that the workers with more severe insomnia symptoms had an earlier timing of DLMO. Finally, SWD subjects were exposed to more morning light (between 05:00 and 11:00?h) as than ANW ones (798 vs. 180 lux [M?±?SD], respectively z?=??1.7; p?<?.05). These data provide evidence of an internal physiological delay of the circadian pacemaker in asymptomatic night-shift workers. In contrast, individuals with SWD maintain a circadian phase position similar to day workers, leading to a mismatch/conflict between their endogenous rhythms and their sleep-wake schedule. (Author correspondence: vgumeny1@hfhs.org)     

Sleep,Sleepiness, and Neurobehavioral Performance While on Watch in a Simulated 4 Hours on/8 Hours off Maritime Watch System

Seafarer sleepiness jeopardizes safety at sea and has been documented as a direct or contributing factor in many maritime accidents. This study investigates sleep, sleepiness, and neurobehavioral performance in a simulated 4?h on/8?h off watch system as well as the effects of a single free watch disturbance, simulating a condition of overtime work, resulting in 16?h of work in a row and a missed sleep opportunity. Thirty bridge officers (age 30?±?6 yrs; 29 men) participated in bridge simulator trials on an identical 1-wk voyage in the North Sea and English Channel. The three watch teams started respectively with the 00–04, the 04–08, and the 08–12 watches. Participants rated their sleepiness every hour (Karolinska Sleepiness Scale [KSS]) and carried out a 5-min psychomotor vigilance test (PVT) test at the start and end of every watch. Polysomnography (PSG) was recorded during 6 watches in the first and the second half of the week. KSS was higher during the first (mean?±?SD: 4.0?±?0.2) compared with the second (3.3?±?0.2) watch of the day (p?<?0.001). In addition, it increased with hours on watch (p?<?0.001), peaking at the end of watch (4.1?±?0.2). The free watch disturbance increased KSS profoundly (p?<?0.001): from 4.2?±?0.2 to 6.5?±?0.3. PVT reaction times were slower during the first (290?±?6?ms) compared with the second (280?±?6?ms) watch of the day (p?<?0.001) as well as at the end of the watch (289?±?6?ms) compared with the start (281?±?6?ms; p?=?0.001). The free watch disturbance increased reaction times (p?<?0.001) from 283?±?5 to 306?±?7?ms. Similar effects were observed for PVT lapses. One third of all participants slept during at least one of the PSG watches. Sleep on watch was most abundant in the team working 00–04 and it increased following the free watch disturbance. This study reveals that—within a 4?h on/8?h off shift system—subjective and objective sleepiness peak during the night and early morning watches, coinciding with a time frame in which relatively many maritime accidents occur. In addition, we showed that overtime work strongly increases sleepiness. Finally, a striking amount of participants fell asleep while on duty.     

The impact of a delayed sleep–wake schedule on depression is greater in women – A web-based cross-sectional study in Japanese young adults

Sleep-related problems, such as symptoms of insomnia, daytime sleepiness, shorter sleep duration, or a delayed sleep–wake schedule, are known to be risk factors for depression. In general, depression is more prevalent in women than in men, but sleep-related problems do not necessarily show similar gender predominance. Hence, it can be speculated that the impact of sleep-related problems on the development process of depression differs between genders; however, so far, few studies have focused on this issue. The aim of this study was to clarify gender differences in the rates of depression of people with the above sleep-related problems, and to examine gender differences in factors associated with depression in Japanese young adults. A web-based questionnaire survey comprising assessments of demographic variables, sleep-related variables (bed time, wake time, sleep onset latency, frequency of difficulty in initiating sleep and that in maintaining sleep, i.e. symptom components of insomnia, and daytime sleepiness), and the 12-item version of the Center for Epidemiologic Studies Depression Scale was administered to 2502 participants (males:females?=?1144:1358, age range?=?19–25 years). Female predominance in the rate of depression was observed only in subjects with a delayed sleep–wake schedule (χ²₍₁₎?=?15.44, p?<?0.001). In men, daytime sleepiness and difficulty in initiating sleep were significantly associated with depression (odds ratio [OR]?=?2.39, 95% confidence interval [CI]?=?[1.69, 3.39], p?<?0.001; OR?=?3.50, 95% CI?=?[2.29, 5.35], p?<?0.001, respectively), whereas in women, significant associations were found between depression and a delayed sleep–wake schedule (OR?=?1.75, 95% CI?=?[1.28, 2.39], p?<?0.001), daytime sleepiness (OR?=?2.13, 95% CI?=?[1.60, 2.85], p?<?0.001), and difficulty in initiating sleep (OR?=?4.37, 95% CI?=?[3.17, 6.03], p?<?0.001). These results indicate that in younger generations, the impact of a delayed sleep–wake schedule on the development of depression is greater in women; specifically, women are vulnerable to depression when they have an eveningness-type lifestyle, which is possibly attributable to the female-specific intrinsic earlier and shorter circadian rhythm. These results suggest the necessity of gender-based approaches to treating sleep-related problems for alleviating or preventing depressive symptoms in young adults.     

Light exposure at night is associated with subclinical carotid atherosclerosis in the general elderly population: The HEIJO-KYO cohort

Epidemiological and cellular biological studies indicate the influence of impaired circadian biological rhythmicity on atherosclerosis. Increased exposure to light at night (LAN) is common in modern life, and LAN exposure is the most important environmental cue for circadian misalignment. However, the association between LAN exposure and atherosclerosis has never been explored in humans. In this cross-sectional study, we measured nighttime light intensity in the bedroom along with the intima-media thickness (IMT) of the common carotid artery using ultrasonography in 700 elderly individuals (mean age 71.6 years). Averages of mean and maximal carotid IMT were 0.88?±?0.15?mm and 1.09?±?0.32?mm, respectively. Median intensity of LAN exposure was 0.74?lux (interquartile range, 0.08–3.34). Both mean and maximal carotid IMT significantly increased across quartiles of increasing LAN intensity (p for trend?=?0.002 and <0.001, respectively). After adjustment for confounding factors, including age, gender, body mass index, current smoking status, hypertension, diabetes, dyslipidemia, sleep medication, estimated glomerular filtration rate, nocturia, bedtime, duration in bed (scotoperiod), day length (photoperiod), urinary 6-sulfatoxymelatonin excretion and daytime and nighttime physical activity, multivariate linear regression models revealed significant associations of LAN exposure with carotid IMT measurements [mean: β, 0.032 (fourth versus first quartiles); 95% confidence intervals (CI), 0.002–0.061; p?=?0.037; maximal: β, 0.100 (fourth versus first quartiles); 95% CI, 0.034–0.165; p?=?0.003]. In conclusion, these results suggested that LAN exposure in home settings is significantly associated with subclinical carotid atherosclerosis in the general elderly population.     

Light Exposure Among Adolescents With Delayed Sleep Phase Disorder: A Prospective Cohort Study

The objective of this study was to compare light exposure and sleep parameters between adolescents with delayed sleep phase disorder (DSPD; n?=?16, 15.3?±?1.8 yrs) and unaffected controls (n?=?22, 13.7?±?2.4 yrs) using a prospective cohort design. Participants wore wrist actigraphs with photosensors for 14 days. Mean hourly lux levels from 20:00 to 05:00?h and 05:00 to 14:00?h were examined, in addition to the 9-h intervals prior to sleep onset and after sleep offset. Sleep parameters were compared separately, and were also included as covariates within models that analyzed associations with specified light intervals. Additional covariates included group and school night status. Adolescent delayed sleep phase subjects received more evening (p?<?.02, 22:00–02:00?h) and less morning (p?<?.05, 08:00–09:00?h and 10:00–12:00?h) light than controls, but had less pre-sleep exposure with adjustments for the time of sleep onset (p?<?.03, 5–7?h prior to onset hour). No differences were identified with respect to the sleep offset interval. Increased total sleep time and later sleep offset times were associated with decreased evening (p?<?.001 and p?=?.02, respectively) and morning (p?=?.01 and p?<?.001, respectively) light exposure, and later sleep onset times were associated with increased evening exposure (p?<?.001). Increased total sleep time also correlated with increased exposure during the 9?h before sleep onset (p?=?.01), and a later sleep onset time corresponded with decreased light exposure during the same interval (p?<?.001). Outcomes persisted regardless of school night status. In conclusion, light exposure interpretation requires adjustments for sleep timing among adolescents with DSPD. Pre- and post-sleep light exposures do not appear to contribute directly to phase delays. Sensitivity to morning light may be reduced among adolescents with DSPD. (Author correspondence: auger.raymond1@mayo.edu)     

Low proportions of folic acid deficiency after introduction of mandatory folic acid fortification in remote areas of northern Queensland,Australia: a secondary health data analysis

Abstract

Background: Australia implemented mandatory folic acid fortification of bread-making flour in 2009.

Objective: To assess the impact of folic acid fortification in remote vs. regional urban areas and Indigenous vs. non-Indigenous populations in northern Queensland.

Methods: Routinely collected data on folic acid measurements in remote areas and two regional urban centres in northern Queensland between 2004 and 2015 were analysed (n?=?13,929) dichotomously (folic deficient vs. non-deficient).

Results: Overall prevalence of folic acid deficiency was 3.2% (235/7282) in urban centres compared with 7.2% (480/6647) in remote areas (p?<?0.001), and 9.3% (393/4240) in the Indigenous population compared with 3.2% (273/8451) in the non-Indigenous population (p?<?0.001). Prevalence of folic acid deficiency dropped from 12.2% (n?=?481) in 2004–2008 to 1.5% (n?=?126) in 2010–2015 (p?<?0.001). This translates into a relative risk reduction (RRR) of 88%. RRR was 79% (7.2% vs. 1.5%) in urban centres, 91% (17.3% vs. 1.5%) in remote areas, 92% (20.5% vs. 1.6%) in the Indigenous population and 80% (7.4% vs. 1.5%) in the non-Indigenous population (p?<?0.001 for all).

Conclusions: Substantial declines of folic acid deficiency to low and comparable proportions in former high-risk populations indicate that mandatory folic acid fortification of flour has had a population-wide benefit in northern Queensland.     

Effect of exposure to evening light on sleep initiation in the elderly: A longitudinal analysis for repeated measurements in home settings

Epidemiologic data have demonstrated associations of sleep-onset insomnia with a variety of diseases, including depression, dementia, diabetes and cardiovascular diseases. Sleep initiation is controlled by the suprachiasmatic nucleus of the hypothalamus and endogenous melatonin, both of which are influenced by environmental light. Exposure to evening light is hypothesized to cause circadian phase delay and melatonin suppression before bedtime, resulting in circadian misalignment and sleep-onset insomnia; however, whether exposure to evening light disturbs sleep initiation in home settings remains unclear. In this longitudinal analysis of 192 elderly individuals (mean age: 69.9 years), we measured evening light exposure and sleep-onset latency for 4 days using a wrist actigraph incorporating a light meter and an accelerometer. Mixed-effect linear regression analysis for repeated measurements was used to evaluate the effect of evening light exposure on subsequent sleep-onset latency. The median intensity of evening light exposure and the median sleep-onset latency were 27.3?lux (interquartile range, 17.9–43.4) and 17?min (interquartile range, 7–33), respectively. Univariate models showed significant associations between sleep-onset latency and age, gender, daytime physical activity, in-bed time, day length and average intensity of evening and nighttime light exposures. In a multivariate model, log-transformed average intensity of evening light exposure was significantly associated with log-transformed sleep-onset latency independent of the former potential confounding factors (regression coefficient, 0.133; 95% CI, 0.020–0.247; p?=?0.021). Day length and nighttime light exposure were also significantly associated with log-transformed sleep-onset latency (p?=?0.001 and p?<?0.001, respectively). In conclusion, exposure to evening light in home setting prolongs subsequent sleep-onset latency in the elderly.     

Effects of Filtering Visual Short Wavelengths During Nocturnal Shiftwork on Sleep and Performance

Circadian phase resetting is sensitive to visual short wavelengths (450–480?nm). Selectively filtering this range of wavelengths may reduce circadian misalignment and sleep impairment during irregular light-dark schedules associated with shiftwork. We examined the effects of filtering short wavelengths (<480?nm) during night shifts on sleep and performance in nine nurses (five females and four males; mean age?±?SD: 31.3?±?4.6 yrs). Participants were randomized to receive filtered light (intervention) or standard indoor light (baseline) on night shifts. Nighttime sleep after two night shifts and daytime sleep in between two night shifts was assessed by polysomnography (PSG). In addition, salivary melatonin levels and alertness were assessed every 2?h on the first night shift of each study period and on the middle night of a run of three night shifts in each study period. Sleep and performance under baseline and intervention conditions were compared with daytime performance on the seventh day shift, and nighttime sleep following the seventh daytime shift (comparator). On the baseline night PSG, total sleep time (TST) (p?<?0.01) and sleep efficiency (p?=?0.01) were significantly decreased and intervening wake times (wake after sleep onset [WASO]) (p?=?0.04) were significantly increased in relation to the comparator night sleep. In contrast, under intervention, TST was increased by a mean of 40?min compared with baseline, WASO was reduced and sleep efficiency was increased to levels similar to the comparator night. Daytime sleep was significantly impaired under both baseline and intervention conditions. Salivary melatonin levels were significantly higher on the first (p?<?0.05) and middle (p?<?0.01) night shifts under intervention compared with baseline. Subjective sleepiness increased throughout the night under both conditions (p?<?0.01). However, reaction time and throughput on vigilance tests were similar to daytime performance under intervention but impaired under baseline on the first night shift. By the middle night shift, the difference in performance was no longer significant between day shift and either of the two night shift conditions, suggesting some adaptation to the night shift had occurred under baseline conditions. These results suggest that both daytime and nighttime sleep are adversely affected in rotating-shift workers and that filtering short wavelengths may be an approach to reduce sleep disruption and improve performance in rotating-shift workers. (Author correspondence: casper@lunenfeld.ca)