Rest-activity rhythm in breast cancer survivors: an update based on non-parametric indices

ABSTRACT

Recently we evaluated by actigraphy the rest-activity circadian rhythm (RAR) in breast cancer (BC) survivors at 5 years from primary diagnosis, as well as in a control group with similar age and body mass index (BMI). RAR, analyzed by Cosinor method, resulted significantly different in BC survivors compared to healthy subjects: BC survivors showed lower values of MESOR and Amplitude (A), while acrophase (φ) was similar in the two groups.

Now, using non-parametric methods we have detected Interdaily Stability (IS), Intradaily Variability (IV), nocturnal activity (L5), and daily activity (M10) on the same sample of previous study: 15 BC survivors at 5 years from the primary diagnosis (mean age = 56.7 ± 6.6 yrs; mean BMI = 24.5 ± 3.8 Kg/m²) and 13 healthy controls (mean age = 54.4 ± 7.2 yrs; mean BMI = 25.2 ± 2.8 Kg/m²).

The non-parametric indices showed that in BC-group IV was significantly higher than in Ctrl-group (0.86 vs. 0.65 a.u. in BC and Ctrl, respectively; p <.01), while L5 (11.27 vs. 34.41 a.c. in BC and Ctrl, respectively; p <.0001) and M10 (326.82 vs. 428.07 a.c. in BC and Ctrl, respectively; p <.01) were significantly lower compared to Ctrl-group.

The data suggest that BC patients need constant clinical assessment of RAR characteristics along the years following the primary diagnosis. The analysis of RAR in all its components, parametric and non-parametric, is important to detect alterations in the sleep-wake cycle and can be useful for developing new strategies for health protection, such as structured and tailored physical activity programs, to improve circadian activity level in order to raise the quality of life in BC survivors.     

Athletes’ rest-activity circadian rhythm differs in accordance with the sport discipline

The correct expression of circadian rhythmicity is crucial for the body homeostasis. The rest-activity circadian rhythms (RARs) are involved in the control of the sleep-wake cycle and altered RARs could lead to a compromised health status. Many studies focused on examining sleep behavior and circadian rhythms in physically active subjects or athletes but, unexpectedly, no data on RARs are available. Therefore, we studied the existence of the RAR in athletes and the possible difference in RAR’s characteristics among sport disciplines. The study had a prospective observational design and RARs were recorded for five consecutive training days through actigraphy (Actiwatch 2 actigraph; Philips Respironics, OR, USA) in 43 athletes (mean age: 25.6 ± 3.2 years). Athletes competed in three different disciplines and had different training schedules and competition levels: professional triathletes (N = 10; 6 females and 4 males) had 2 morning (08:30–12:00) and 1 afternoon (15:00–17:00) training sessions, professional volleyball players (N = 19; 12 females and 7 males) used to train once in the morning (09:00–11:30) and once in the afternoon (15:00–18:00), and non-professional soccer players (N = 14; all males) trained always late in the evening (20:30–22:30). To determine the existence of RARs, the activity counts (A.C.) data were analyzed using the single and the population mean cosinor method; a one-way analysis of variance (ANOVA) followed by the Tukey–Kramer post-hoc test was used for the comparison of RAR characteristics among soccer, volleyball and triathlon athletes. Partial eta squared (?_p²) was used to determine the magnitude of the effect for significant outcomes (α = 0.05) in ANOVA. The presence of a significant RAR both for each of the 43 athletes (p < 0.001) and for the three categories of athletes (p < 0.001) was observed. RARs differed among sport disciplines: the Midline Estimating Statistic of Rhythm (MESOR) was significantly higher in triathletes (mean: 347 A.C. with 95% Confidence Interval [CI]: 314–379) compared to both volleyball (mean: 188 A.C. with 95% CI: 173–203; p < 0.001) and soccer players (mean: 289 A.C. with 95% CI: 267–312; p < 0.01) with ?_p² = 0.72. Amplitude (A) values showed the same significant trend of MESOR data (ANOVA: p < 0.001; ?_p² = 0.65) while the acrophase (Φ) occurred at 18:28 for soccer players, significantly later than triathlon (15:20 h; p < 0.001) and volleyball players (16:24 h; p < 0.001) (ANOVA: p < 0.001; ?p2 = 0.84). The higher training duration and intensity reached by triathlon athletes in the morning sessions caused a phase advance of their RAR’s acrophase Φ and higher MESOR and A amplitude compared to volleyball players and triathletes. Therefore, different sport disciplines require different training schedules, training loads and intensities that translate into different RARs. Strength coaches and medical staff of professional teams should strongly consider actigraphy as a practical and powerful tool to monitor RARs, sleep behavior, and the activity levels of their athletes; highlighting potential circadian disruptions through actigraphy could be helpful to prevent musculoskeletal injuries.     

Subjective and objective sleep among air ambulance personnel

ABSTRACT

The present study aimed to investigate the effects of shift work on sleep among pilots and Helicopter Emergency Medical Service crew members (HCM) in the Norwegian Air Ambulance. Sleep was assessed by diaries and actigraphy during a workweek (24 h duty for 7 consecutive days) in the winter season and a workweek during the summer season in pilots and HCM (N = 50). Additionally, differences in sleep were studied between the week before work, the workweek, and the week after work in both seasons. Results indicated that bedtime was later (p <.001) and time spent in bed (p <.05) was shorter during the summer, compared to the winter, season. The workers delayed the sleep period in the workweek, compared to the week before (winter: p <.001, summer: p <.001) and the week after (winter: p <.05-.001, summer: p <.001). They spent more time in bed during the workweek, compared to the week before (winter: p <.001, summer: p <.01) and after (winter: p <.001, summer: p =.37). Further, the workers had longer wake after sleep onset during the workweek, compared to the week before (winter: p <.001, summer: p <.01) and the week after (winter: p <.01, summer: p <.01). Finally, the workers had lower sleep efficiency during the workweek recorded by actigraphy compared to the week before (winter: p <.01, summer: p <.001) and the week after (winter: p <.01, summer: p <.001). According to the sleep diaries the total sleep time was 7:17 h in the winter and 7:03 h in the summer season. Overall, the sleep was somewhat affected during the workweek, with delayed sleep period, longer wake after sleep onset, and lower sleep efficiency compared to when off work. However, the workers spent more time in bed during the workweek compared to the weeks off, and they obtained over 7 h of sleep in both workweeks. Our findings suggest that the pilots and the HCM sleep well during the workweek, although it affected their sleep to some extent.     

Variations in rest-activity rhythm are associated with clinically measured disease severity in Parkinson’s disease

ABSTRACT

The continuous, longitudinal nature of accelerometry monitoring is well-suited to capturing the regular 24-hour oscillations in human activity across the day, the cumulative effect of our circadian rhythm and behavior. Disruption of the circadian rhythm in turn disrupts rest-activity rhythms. Although circadian disruption is a major feature of Parkinson’s disease (PD), rest-activity rhythms and their relationship with disease severity have not been well characterized in PD. 13 PD participants (Hoehn & Yahr Stage [H&Y] 1–3) wore a Philips Actiwatch Spectrum PRO continuously for two separate weeks. Rest-activity rhythms were quantified by fitting an oscillating 24-hour cosinor model to each participant-day of activity data. One-way ANOVAs adjusted for demographics revealed significant variation in the amount (MESOR, F = 12.76, p < .01), range (Amplitude, F = 9.62, p < .01), and timing (Acrophase, F = 2.7, p = .05) of activity across H&Y Stages. Those with higher H&Y Stages were significantly more likely to be active later in the day, where-as those who shifted between H&Y Stages during the study were significantly more active than those who did not change H&Y Stage. Being active later in the day was also significantly associated with higher scores on the Movement Disorder Society’s Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) Section III (motor symptom severity, p = .02), Section II (self-reported impact of motor symptoms on daily living, p = .01), and Total Score (p = .01) in an adjusted linear regression model; significant associations between MDS-UPDRS scores and activity levels were observed only in the unadjusted model. These findings demonstrate that continuous actigraphy is capable of detecting rest-activity disruption in PD, and provides preliminary evidence that rest-activity rhythms are associated with motor symptom severity and H&Y Stage.     

Effects of environmental enrichment on activity and lameness in commercial broiler production

The aim of this pilot study was to investigate the effects of commercially applied environmental enrichments on behavior and lameness in broilers. Two consecutive flocks of broilers were observed at 16 days and 30 days of age to investigate differences between enriched (peat, bales of lucerne hay, and elevated platforms) and control birds with regards to behavioral activities and lameness. More running (p < .001), worm running (p = .006), play fighting (p = .015), dust bathing (p = .009), and ground pecking while standing (p < .001) were observed at 16 days than at 30 days. Across both ages, enriched birds showed more wing flapping (p = .016), wing stretching (p = .002), body shaking (p = .002), ground scratching (p < .001), and ground pecking while standing (p < .001) and lying (p = .003) compared with control birds. Even when no enrichments were close, enriched birds showed more body shaking (p = .008) and ground pecking while standing (p < 0.001) and lying (p = .010) than birds in comparable locations in control pens. There was a tendency for a lower gait score (i.e., reduced lameness) with the enriched treatment (p = .077). In conclusion, enriched birds showed higher levels of several activities compared with control birds, and demonstrated higher levels in areas where no enrichments were present.     

Effect of Adopters' Lifestyles and Animal-Care Knowledge on Their Expectations Prior to Companion-Animal Guardianship

Human expectations can greatly affect the human–companion animal relationship, sometimes putting nonhuman animals at risk for relinquishment. At 20 animal shelters in Southern Ontario, Canada, potential adopters (N = 234) completed a questionnaire regarding their lifestyle, companion animal-care knowledge, and preadoption expectations of their adopted companion animals. Linear mixed models were used to assess the associations of adopters' lifestyles and companion animal-care knowledge with their expectations for animal behavior, the human–companion animal relationship, and the effort required in companion-animal guardianship. Dog adopters had higher expectations than cat adopters for their companion animal's behavior (p < .001), the human–companion animal relationship (p < .001), and the effort required in companion-animal guardianship (p < .001). Adopters' human relationship statuses were also associated with expectations for the human–companion animal relationship (p = .002). As adopters' companion animal-care knowledge increased, so did their expectations for the effort required in companion-animal guardianship (p < .001). An understanding of adopters' expectations prior to adoption will help animal shelters better match, educate, and prepare adopters for their lives with companion animals.     

Differences in workday sleep fragmentation,rest-activity cycle,sleep quality,and activity level among nurses working different shifts

ABSTRACT

Schedule changes associated with rotating shifts can interfere with the circadian rhythms of nurses and thereby affect their sleep duration, sleep quality, work efficiency, and work performance. The objectives of this study was to investigate differences in workday sleep fragmentation, rest-activity cycle, sleep quality, and activity level among nurses working different shifts. After filling out a basic information questionnaire and completing the Pittsburgh Sleep Quality Index (PSQI) questionnaire, participants were asked to wear an actigraph and keep sleep records for seven consecutive days. Data pertaining to wake after sleep onset (WASO), 24-hour autocorrelation coefficient (r24), and daytime activity mean was collected in order to investigate workday sleep fragmentation, rest-activity cycle, and daytime activity level. We obtained complete questionnaires and data from 191 nurses. Day- and evening-shift nurses had more regular workday rest-activity cycles than did night-shift nurses (F = 51.26, p < .001). After controlling for r24 coefficients, we determined that nurses who experienced greater workday sleep fragmentation had higher PSQI scores (β = .18, p = .008). After controlling for WASO times, we determined that nurses who had more regular rest-activity cycles on workdays had lower PSQI scores (β = – .16, p = .036). After controlling for shift type and WASO times, we determined that nurses with higher PSQI scores displayed lower activity levels (β = – .21, p = .015) and those with higher r24 coefficients displayed higher activity levels (β = .18, p = .040) on workdays. We then examined the causal path relationships. Among the shifts, only the day-shift nurses had a higher r24 (β = ?.59, p < .001) than did the night-shift nurses; WASO exerted a significant impact on PSQI scores (β = .20, p = .002); r24 had a significant and negative influence on PSQI scores (β = ?.38, p < .001), and PSQI scores significantly and negatively influenced workday activity levels (β = ?.20, p = .006). This study determined that day- and evening-shift nurses enjoyed more regular and consistent rest-activity cycles than did night-shift nurses; nurses with greater workday sleep fragmentation and/or more irregular rest-activity cycles experienced poorer sleep quality; and nurses suffering from poorer sleep quality displayed lower daytime activity levels on workdays.     

Altering meal timing to improve cognitive performance during simulated nightshifts

ABSTRACT

Altering meal timing could improve cognition, alertness, and thus safety during the nightshift. This study investigated the differential impact of consuming a meal, snack, or not eating during the nightshift on cognitive performance (ANZCTR12615001107516). 39 healthy participants (59% male, age mean±SD: 24.5 ± 5.0y) completed a 7-day laboratory study and underwent four simulated nightshifts. Participants were randomly allocated to: Meal at Night (MN; n= 12), Snack at Night (SN; n = 13) or No Eating at Night (NE; n = 14). At 00:30 h, MN consumed a meal and SN consumed a snack (30% and 10% of 24 h energy intake respectively). NE did not eat during the nightshift. Macronutrient intake was constant across conditions. At 20:00 h, 22:30 h, 01:30 h, and 04:00 h, participants completed the 3-min Psychomotor Vigilance Task (PVT-B), 40-min driving simulator, post-drive PVT-B, subjective sleepiness scale, 2-choice Reaction Time task, and Running Memory task. Objective sleep was recorded for each of the day sleeps using Actigraphy and for the third day sleep, Polysomnography was used. Performance was compared between conditions using mixed model analyses. Significant two-way interactions were found. At 04:00 h, SN displayed increased time spent in the safe zone (p < .001; percentage of time spent within 10 km/h of the speed limit and 0.8 m of lane center), and decreases in speed variability (p < .001), lane variability (p < .001), post-drive PVT-B lapses (defined as RT > 355 ms; p < .001), and reaction time on the 2-choice reaction time task (p < .001) and running memory task (p < .001) compared to MN and NE. MN reported greater subjective sleepiness at 04:00 h (p < .001) compared to SN and NE. There was no difference in objective sleep between eating conditions. Eating a large meal during the nightshift impairs cognitive performance and sleepiness above the effects of time of night alone. For improved performance, shiftworkers should opt for a snack at night.     

Population-level study links short-wavelength nighttime illumination with breast cancer incidence in a major metropolitan area

ABSTRACT

Several population-level studies revealed a positive association between breast cancer (BC) incidence and artificial light at night (ALAN) exposure. However, the effect of short-wavelength illumination, implicated by laboratory research and small-scale cohort studies as the main driving force behind BC–ALAN association, has not been supported by any population-level study carried out to date. We investigated a possible link between BC and ALAN of different subspectra using a multi-spectral year-2011 satellite image, taken from the International Space Station, and superimposing it with year-2013 BC incidence data available for the Great Haifa Metropolitan Area in Israel. The analysis was performed using both ordinary least square (OLS) and spatial dependency models, controlling for socioeconomic and locational attributes of the study area. The study revealed strong associations between BC and blue and green light subspectra (B = 0.336 ± 0.001 and B = 0.335 ± 0.002, respectively; p < 0.01), compared to a somewhat weaker effect for the red subspectrum (B = 0.056 ± 0.001; p < 0.01). However, spatial dependency models, controlling for spatial autocorrelation of regression residuals, confirmed only a positive association between BC incidence and short-wavelength (blue) ALAN subspectrum (z = 2.462, p < 0.05) while reporting insignificant associations between BC and either green (z = 1.425, p > 0.1) or red (z = ?0.604, p > 0.1) subspectra. The obtained result is in line with the results of laboratory- and small-scale cohort studies linking short-wavelength nighttime illumination with circadian disruption and melatonin suppression. The detected effect of blue lights on BC incidence may help to develop informed illumination policies aimed at minimizing the adverse health effects of ALAN exposure on human health.     

Rest-activity rhythms characteristics and seasonal changes in seasonal affective disorder

ABSTRACT

Identifying objectively measurable seasonal changes in 24-h activity patterns (rest-activity rhythms or RARs) that occur in seasonal affective disorder (SAD) could help guide research and practice towards new monitoring tools or prevention targets. We quantified RARs from actigraphy data using non-parametric and extended cosine based approaches, then compared RARs between people with SAD and healthy controls in the summer (n = 70) and winter seasons (n = 84). We also characterized the within-person seasonal RAR changes that occurred in the SAD (n = 19) and control (n = 26) participants who contributed repeated measures. Only controls had significant winter increases in RAR fragmentation (intra-daily variability; in controls mean winter-summer changes (log scale) = 0.05, 0.21 standard deviation, p = 0.03). In SAD participants only, estimated evening settling times (down-mesor) were an average of 30 min earlier in the winter compared with the summer (1-h standard deviation, p = 0.045). These RAR characteristics correlated with greater fatigue (Spearman r = 0.36) but not depression symptom severity. Additional research is needed to ascertain why healthy controls, but not people with SAD, appear to have increased RAR fragmentation in the winter. People with SAD lacked this increase in RAR fragmentation, and instead had earlier evening setting in the winter. Prospective and intervention studies with greater temporal resolution are warranted to ascertain how these seasonal behavioral differences relate to fatigue pathophysiology in SAD. Future research is needed to determine whether extending the winter active period, even in relatively fragmented bouts, could help reduce the fatigue symptoms common in SAD.     

A Cross-Sectional Epidemiological Study of Prevalence and Severity of Bit-Induced Oral Trauma in Polo Ponies and Race Horses

Bit and bridle accessories improperly fitted in ridden horses can cause oral trauma such as bone spurs, commissure ulceration, and tongue lacerations. This study was used to identify, grade, and compare the types of oral traumas commonly found within polo ponies and race horses. Injuries were assessed visually and by palpation on the tongue, lips’ commissures, and interdental space. A total of 50 polo ponies and 50 race horses were sampled in the South of England. A Poisson model was successfully fitted to the data (p < .001), and the variables of discipline (p < .001), injury type (p < .001), and age (p < .001) were significant. Race horses with snaffle bits were predisposed to significantly higher severities and prevalence of oral trauma than were polo ponies in gag bits. Only polo ponies were observed with tongue trauma. Race horses had higher severities of injuries in the commissures and bone spurs. Positive correlations were found between age and/or time in sport and induced biting injuries. Polo ponies had been playing longer before the occurrence of injuries.     

Effects of shift work on attention deficit,hyperactivity, and impulsivity,and their relationship with chronotype

There is growing evidence that shift-work schedules cause severe disturbances to circadian rhythms and the sleep–wakefulness cycle, and that these changes in turn lead to cognitive and behavioral problems. The objective of this study is to explore the relationships between biological rhythm differences (chronotype) and impulsive behaviors and attention-deficit hyperactivity symptoms in shift workers. Seventy-nine nurses working in the daytime and 127 nurses working on night shifts were evaluated with the Barratt Impulsiveness Scale, Adult Attention Deficit Hyperactivity Disorder Self-Report Scale (ASRS), and Morningness–Eveningness questionnaire for identifying circadian preference. It was found that shift workers had more attention deficit (p < .05) and impulsivity (p < .01) when compared with daytime workers. Morning-type workers reported lower hyperactivity and ASRS total scores than evening- and intermediate-type workers. The mean impulsivity score of evening-type workers was higher than both the other groups (p < .05). It has been shown that attention deficit, hyperactivity, and impulsivity levels that appear as a result of working shifts might change in accordance with the individual’s chronotype. It might, therefore, be desirable to evaluate an individual’s chronotype to establish suitability for working shifts.     

Rhythmic changes in Fabry disease: Inversion and non-oscillatory pattern in 6-sulfatoxymelatonin daily profile

Fabry disease is a progressive disease characterized by an enzymatic deficiency of acid alpha-galactosidase and glycosphingolipids storage within the lysosomes. The disease has two phenotypes: classic and nonclassic. Excessive daytime sleepiness is a common sign reported by patients and can be caused by a circadian rhythm sleep disorder. Activity and rest cycle, variation of body temperature and melatonin biosynthesis are known rhythmicity markers. In the face of these evidences, our goal was to evaluate the rhythmic profile in Fabry’s disease patients using rhythmicity markers. For this purpose, we recruited 17 patients diagnosed with Fabry disease (11 classic and 6 nonclassic variant) that answered the Epworth Sleepiness Scale and the Morningness–Eveningness questionnaire adapted from Horne and Ostberg; recorded activity and body temperature rhythms by an actigraphy during at least 10 days and collected urine to assess 6-sulfatoxymelatonin excretion load during the day (from the second urine in the morning until 7 p.m.) and night (starting from 7 p.m. until the first urine in the morning of the following day). We observed that control subjects presented higher excretion load of 6-sulfatoxymelatonin during the night (p < 0.05, d = 7.8), as expected. Patients with the nonclassic variant presented an inversion on 6-sulfatoxymelatonin daily profile (p < 0.05, d = 3.8) and there was no difference between the day and night profile of classic variant patients when compared to the other two groups. Patients with the classic variant also presented temperature period greater than 24 hours (p < 0.05, d = 2.0). Therefore, we came to the conclusion that there is an alteration in the circadian rhythms in Fabry disease patients, evidenced by modifications in the 6-sulfatoxymelatonin daily profile and in the body temperature rhythm period.     

Circadian rhythm gene expression and daily melatonin levels vary in athletes and sedentary males

The circadian rhythm is a 24-h cycle in which cells control metabolic and physiological processes throughout the day. In this study, we compared the expression patterns of major circadian rhythm-related genes: from blood of Bmal1, Ror-α, Cry1, Per2, Per1, and Nr1d1. In addition, changes in patterns of melatonin levels were observed in 16 subjects, eight males rugby players and eight males who did not exercise regularly. Blood was collected at 6:00, 10:00, 18:00, and 22:00. Bmal1, Ror-α, Cry1, Per2 (p < 0.001), Per1 (p < 0.01), and Nr1d1 (p < 0.05) genes related to circadian rhythm was higher in rugby players than in sedentary males. However, melatonin levels were higher in sedentary males than in rugby players (p < 0.05). These results indicate that long-term exercise in athletes can increase the expression of genes related to circadian rhythm and these may have an effect on daily melatonin levels as well.     

The cyanobacterium Oscillatoria brevis β-carotene extract modulates alterations of biochemical and hematological circadian patterns in stress-induced rat

Managing stress can prevent serious health problems. The present study aimed to evaluate the possible protective effect of β-carotene (βC), as a natural cyanobacterial product, against stress-induced alterations in biochemical and hematological circadian patterns. Male albino rats were subjected to chronic unpredictable stress (CUS) for 21 days. Rats were randomly divided into four groups (20 rats/group), viz. control, CUS exposed, βC-treated, and βC-treated + CUS-exposed groups. Before CUS exposure, Oscillatoria brevis βC extract was administered (10 mg/kg), intraperitoneally. Blood samples were collected at four Zeitgeber times (ZT: 3, 9, 15 and 21), 5 rats/time point, to monitor circadian profiles of aspartate transferase (AST), alanine transferase (ALT), total protein (TP), glucose (Glu), urea, creatinine, lactate dehydrogenase (LDH), creatinine kinase-MB (CK-MB), hemoglobin (Hb), hematocrite (HCV), red blood cell (RBCs), and white blood cell counts (WBCs). Results revealed that these parameters expressed circadian patterns. CUS exposure significantly (p < 0.05) increased AST, ALT, Glu, urea, creatinine, LDH, CK-MB, and HCV. On the other hand, it significantly decreased Hb, RBCs, and WBCs (p < 0.05). Furthermore, under CUS-exposure the peak time (acrophase) of circadian rhythms of all parameters was variably shifted. On the other hand, βC administration modulated these alternations, where data analysis confirmed a significant decrease in AST, ALT, Glu, urea, creatinine, LDH, CK-MB, and HCV, however, a significant increase in TP, Hb, RBCs, and WBCs (p < 0.05) was observed. Taken together, it can be concluded that βC administration caused restoration of acrophase and level of these parameters thus regulating their circadian rhythms in CUS-induced rats.     

Instituting Dark-Colored Cover to Improve Central Space Use Within Guinea Pig Enclosure

Domestic guinea pigs (Cavia aperea f. porcellus) in laboratories have been shown to actively avoid the centers of their cages. This experiment tested a novel, dark-colored “shader” placed over the central portion of a cage. Based on the observed behavior of wild guinea pig species, it was hypothesized that utilization of the central portion of the cage would increase when the shader was present. Eleven male and 11 female albino, 3-week-old Hartley guinea pigs (Crl:HA) experienced the control and treatment conditions in a crossover study design. They spent more time in central cage sections when the shader was present and spent more time in and around the food hopper when the shader was absent (p < .001). Differences between sexes included increased inactivity in males versus females (p < .05) and a difference in time spent in a corner section of the cage (p < .001), likely associated with location in the room. We concluded that the presence of a shader increased utilization of cage space, which appeared to provide a similar increase in space utilization as structural enrichments.     

Preliminary report; Comparison of the circadian rest-activity rhythm of elderly Japanese community-dwellers according to sarcopenia status

ABSTRACT

We investigated in a preliminarily study the circadian rest-activity rhythm of elderly Japanese community-dwellers according to sarcopenia status based upon the 2019 updated classification criteria of the Asian Working Group for Sarcopenia. A total of 30 participants were recruited from a single rehabilitation center in northern Japan between July and November 2019. The rest-activity rhythm of those with and without sarcopenia was assessed for 7 consecutive 24 h spans by wrist actigraphy in free-living condition and gait performance in the clinic. As group phenomena, the circadian activity rhythm of the sarcopenia cohort (N = 11) was of significantly lower amplitude and more fragmented than the non-sarcopenia cohort (N = 19). The nonparametric circadian rest activity (RAR) parameters of intra-daily variability (IV), relative amplitude (RA), most active 10-h span (M10), and the least active 5-h span (L5), but not interdaily stability (IS), of the sarcopenia group, were all significantly worse than those of the non-sarcopenia group. Gait performance for the sarcopenia group correlated strongly with the fragmentation and altered amplitude of the RAR. These preliminary findings motivated future longitudinal investigation both to improve the detection of sarcopenia in community dwelling elderly and to inform novel preventive or rehabilitative strategies.     

Psychophysical measure of visual luminance contrast during a daily rhythm

ABSTRACT

This study evaluated visual sensitivity to luminance contrast during a daily period. Twenty-eight young male adults (M = 24.85; SD = 2.4) with normal color vision and 20/20 visual acuity participated in this study. The circadian pattern was assessed using the Karolinska Sleepiness Scale (KSS), the Pittsburgh Sleep Quality Index (PSQI), and a sleep diary. To measure the luminance contrast, we used version 11.0 of the Metropsis software with sine-element frequency stimuli for spatial frequencies of 0.2, 0.6, 1, 3.1, 6.1, 8.8, 13.2, and 15.6 cycles per degree of visual angle (cpd). The stimuli were presented on a 19-inch color cathode ray tube (CRT) video monitor with a resolution of 1024 × 786 pixels, an update rate of 100 Hz, and a photopic luminance of 39.6 cd/m2. There was a significant difference in KSS on the weekdays [χ2₍₂₎ = 20.27; p = .001] and in the luminance contrast for frequencies of 13.2 cpd [χ2₍₂₎ = 8.27; p = .001] and 15.6 cpd [χ2₍₂₎ = 13.72; p = .041]. The results showed greater stability of the measurement during the afternoon and a reduction in the visual sensitivity in the high spatial frequencies during the night.     

Internal Desynchronization of Circadian Rhythms and Tolerance to Shift Work

Intolerance to shift work may result from individual susceptibility to an internal desynchronization. Some shift workers (SW) who show desynchronization of their circadian rhythms (e.g., sleep‐wake, body temperature, and grip strength of both hands) exhibit symptoms of SW intolerance, such as sleep alteration, persistent fatigue, sleep medication dependence, and mood disturbances, including depression. Existing time series data previously collected from 48 male Caucasian French SW were reanalyzed specifically to test the hypothesis that internal synchronization of circadian rhythms is associated with SW intolerance and symptoms. The entry of the subjects into the study was randomized. Three groups were formed thereafter: SW with good tolerance (n=14); SW with poor tolerance, as evident by medical complaints for at least one year (n=19); and former SW (n=15) with very poor tolerance and who had been discharged from night work for at 1.5 yr span but who were symptom‐free at the time of the study. Individual and longitudinal time series of selected variables (self‐recorded sleep‐wake data using a sleep log, self‐measured grip strength of both hands using a Colin Gentile dynamometer, and oral temperature using a clinical thermometer) were gathered for at least 15 days, including during one or two night shifts. Measurements were performed 4–5 times/24 h. Power spectra that quantify the prominent period (τ) and t‐test, chi square, and correlation coefficient were used as statistical tools. The mean (±SEM) age of SW with good tolerance was greater than that of SW with poor tolerance (44.9±2.1 yrs vs. 40.1±2.6 yrs, p<.001) and of former SW discharged from night work (very poor tolerance; 33.4±1.7, p<.001). The shift-work duration (yrs) was longer in SW with good than poor tolerance (19.9±2.2 yrs vs. 15.7±2.2; p<0.002) and former SW (10.7±1.2; p<.0001). The correlation between subject age and shift-work duration was stronger in tolerant SW (r=0.97, p<.0001) than in non‐tolerant SW (r=0.80, p<0.001) and greater than that of former SW (r=0.72, p<.01). The mean sleep‐wake rhythm τ was 24 h for all 48 subjects. The number of desynchronized circadian rhythms (τ differing from 24 h) was greater in non‐tolerant than in tolerant SW (chi square=38.9, p<.0001). In Former SW (i.e., 15 individuals assessed in follow‐up studies done 1.5 to 20 yrs after return to day work), both symptoms of intolerance and internal desynchronization were reduced or absent. The results suggest that non‐tolerant SW are particularly sensitive to the internal desynchronization of their circadian time organization.