Circadian Rest-activity Rhythm Research Articles

Associations between accelerometer-measured circadian rest-activity rhythm, brain structural and genetic mechanisms, and dementia.

Knowledge of how circadian rhythm influences brain health remains limited. We aimed to investigate the associations of accelerometer-measured circadian rest-activity rhythm (CRAR) with incident dementia, cognitive dysfunction, and structural brain abnormalities in the general population and underlying biological mechanisms. Fifty-seven thousand five hundred and two participants aged over 60 years with accelerometer data were included to investigate the association of CRAR with incidental dementia. Non-parametric CRAR parameters were utilized, including activity level during active periods of the day (M10), activity level during rest periods of the day (L5), and the relative difference between the M10 and L5 (relative amplitude, RA). Associations of CRAR with cognitive dysfunction and brain structure were studied in a subset of participants. Neuroimaging-transcriptomics analysis was utilized to identify the underlying molecular mechanisms. Over 6.86 (4.94-8.78) years of follow-up, 494 participants developed dementia. The risk of incident dementia was associated with decreasing M10 (hazard ratio [HR] 1.45; 95% conference interval [CI], 1.28-1.64) and RA (HR 1.37; 95% CI, 1.28-1.64), increasing L5 (HR 1.14, 95% CI 1.07-1.21) and advanced L5 onset time (HR 1.12; 95% CI, 1.02-1.23). The detrimental associations were exacerbated by APOE ε4 status and age (>65 years). Decreased RA was associated with lower processing speed (Beta -0.04; SE 0.011), predominantly mediated by abnormalities in subcortical regions and white matter microstructure. The genes underlying CRAR-related brain regional structure variation were enriched for synaptic function. Our study underscores the potential of intervention targeting at maintaining a healthy CRAR pattern to prevent dementia risk.

0001 Circadian Rest-Activity Rhythm Patterns and Physical Performance in Community-Dwelling Older Men

0001 Circadian Rest-Activity Rhythm Patterns and Physical Performance in Community-Dwelling Older Men

Sleep and Circadian Health of Critical Survivors: A 12-Month Follow-Up Study.

To investigate the sleep and circadian health of critical survivors 12 months after hospital discharge and to evaluate a possible effect of the severity of the disease within this context. Observational, prospective study. Single-center study. Two hundred sixty patients admitted to the ICU due to severe acute respiratory syndrome coronavirus 2 infection. None. The cohort was composed of 260 patients (69.2% males), with a median (quartile 1-quartile 3) age of 61.5 years (52.0-67.0 yr). The median length of ICU stay was 11.0 days (6.00-21.8 d), where 56.2% of the patients required invasive mechanical ventilation (IMV). The Pittsburgh Sleep Quality Index (PSQI) revealed that 43.1% of the cohort presented poor sleep quality 12 months after hospital discharge. Actigraphy data indicated an influence of the disease severity on the fragmentation of the circadian rest-activity rhythm at the 3- and 6-month follow-ups, which was no longer significant in the long term. Still, the length of the ICU stay and the duration of IMV predicted a higher fragmentation of the rhythm at the 12-month follow-up with effect sizes (95% CI) of 0.248 (0.078-0.418) and 0.182 (0.005-0.359), respectively. Relevant associations between the PSQI and the Hospital Anxiety and Depression Scale (rho = 0.55, anxiety; rho = 0.5, depression) as well as between the fragmentation of the rhythm and the diffusing lung capacity for carbon monoxide (rho = -0.35) were observed at this time point. Our findings reveal a great prevalence of critical survivors presenting poor sleep quality 12 months after hospital discharge. Actigraphy data indicated the persistence of circadian alterations and a possible impact of the disease severity on the fragmentation of the circadian rest-activity rhythm, which was attenuated at the 12-month follow-up. This altogether highlights the relevance of considering the sleep and circadian health of critical survivors in the long term.

Real-world Digital Biomarkers Index Circadian Rest-activity Rhythms in Persons Taking Dopaminergic Medications for Parkinson’s Disease (P11-3.007)

Real-world Digital Biomarkers Index Circadian Rest-activity Rhythms in Persons Taking Dopaminergic Medications for Parkinson’s Disease (P11-3.007)

Circadian rest-activity rhythms associated with affect and cognition in stroke survivors: An ambulatory assessment study

Circadian rest-activity rhythms associated with affect and cognition in stroke survivors: An ambulatory assessment study

Associations of Circadian Rest-Activity Rhythms With Affect and Cognition in Community-Dwelling Stroke Survivors: An Ambulatory Assessment Study

Background Rest-activity rhythm (RAR) is a modifiable behavioral factor associated with affect and cognition. Identifying RAR characteristics associated with affect and cognition among stroke survivors provides insight into preventing poststroke affective and cognitive impairment. Objective To examine the associations of RAR characteristics with affect and cognition among community-dwelling stroke survivors. Methods Forty participants with mild stroke (mean age = 52.8; 42.5% female; 55% White) reported their affect and cognitive complaints using ecological momentary assessment and wore an accelerometer for 7 consecutive days and completed the National Institutes of Health Toolbox Cognition Battery. RAR characteristics were extracted using parametric and non-parametric approaches. Multivariable linear regressions were used to identify RAR characteristics associated with affect and cognition. Results Later onset of rest (B = 0.45; P = .008) and activity (B = 0.36; P = .041) were positively associated with depressed affect. These associations were reversed for cheerful effect (rest onset: B = −0.42; P = .017; activity onset: B = −0.39; P = .033). Cheerful affect was also positively associated with relative amplitude (ie, distinctions in activity levels between rest and activity; B = .39; P = .030). Intra-daily variability (ie, RAR fragmentation; B = 0.35; P = .042) and later onset of activity (B = .36; P = .048) were positively associated with cognitive complaints. Less erratic RAR was positively associated with fluid cognition (B = 0.29; P = .036); RAR fragmentation was positively associated with crystallized cognition (B = 0.39; P = .015). Conclusions We identified RAR correlates of affect and cognition among stroke survivors, highlighting the value of managing RAR and sleep in stroke rehabilitation. Future studies should test whether advancing the onset of rest and activity, promoting a regular active lifestyle, and improving rest and sleep in the nighttime protect stroke survivors from affective and cognitive impairment.

Individual-specific change points in circadian rest-activity rhythm and sleep in individuals tapering their antidepressant medication: an actigraphy study

Group-level studies showed associations between depressive symptoms and circadian rhythm elements, though whether these associations replicate at the within-person level remains unclear. We investigated whether changes in circadian rhythm elements (namely, rest-activity rhythm, physical activity, and sleep) occur close to depressive symptom transitions and whether there are differences in the amount and direction of circadian rhythm changes in individuals with and without transitions. We used 4 months of actigraphy data from 34 remitted individuals tapering antidepressants (20 with and 14 without depressive symptom transitions) to assess circadian rhythm variables. Within-person kernel change point analyses were used to detect change points (CPs) and their timing in circadian rhythm variables. In 69% of individuals experiencing transitions, CPs were detected near the time of the transition. No-transition participants had an average of 0.64 CPs per individual, which could not be attributed to other known events, compared to those with transitions, who averaged 1 CP per individual. The direction of change varied between individuals, although some variables showed clear patterns in one direction. Results supported the hypothesis that CPs in circadian rhythm occurred more frequently close to transitions in depression. However, a larger sample is needed to understand which circadian rhythm variables change for whom, and more single-subject research to untangle the meaning of the large individual differences.

Sleep, Mental Health, and Cognition Across Diverse Adult Populations

Abstract Sleep is often impaired in late life, raising concerns about the effect of poor sleep on mental and cognitive health in aging individuals. This symposium brings together five rigorous studies that show how poor sleep may be an under-recognized risk factor for mental health and cognitive outcomes in the second half of life. Specifically, this symposium showcases data from a variety of study cohorts (including Midlife in the United Study, Einstein Aging Study, and Study of Muscle, Mobility, and Aging), using diverse indicators of subjective and objective sleep. Paper 1 focuses on healthcare workers (HCWs), a group critical for the delivery of quality patient care, and examines both individual and joint associations of poor sleep and pain with mental health in HCWs vs. non-HCWs. Paper 2 investigates the association between EEG-measured sleep and depressive symptoms in older adults. Paper 3 explores the relationship between intra-individual variability of sleep and mild cognitive impairment (MCI) and identifies gender differences in these associations. Paper 4 establishes the associations of actigraphy-measured sleep and circadian rest-activity rhythms with multiple domains of cognition in older adults. Paper 5 examines the effect of latent dose/duration patterns of common sleep medications on development of Alzheimer’s disease and related dementias. The discussant, Dr. Adam Spira, will integrate key findings from these studies, discuss their contributions to the literature, and consider opportunities for future research. This is a Sleep, Circadian Rhythms and Aging Interest Group Sponsored Symposium. This is a collaborative symposium between the Alzheimer’s Disease and Related Dementias, Geroscience, and Health Behavior Change Interest Groups.

OBJECTIVE SLEEP AND CIRCADIAN REST–ACTIVITY RHYTHMS AND MULTIPLE DOMAINS OF COGNITIVE FUNCTION IN OLDER ADULTS

Abstract Evidence suggests that sleep and circadian rest-activity rhythms (RAR) play a key role in dementia and Alzheimer Disease (AD) pathology. Studies with objective measures of sleep and RAR and multiple domains of cognition remain limited. We studied 820 older adults enrolled in the Study of Muscle, Mobility and Aging (SOMMA). Actigraphs were worn for one week, and processed for sleep-wake measures including total sleep time (TST) and sleep efficiency (SE); and parametric (acrophase, pseudo-F) and non-parametric (interdaily stability [IS], intradaily variability [IV], and relative amplitude [RA]) 24-hour RAR variables. Cognitive assessments included global cognition (the Montreal Cognitive Assessment), executive function (Trails B test), memory (California Verbal Learning Test-short form; and psychomotor performance (Digit-Symbol Coding Test). Adjusting for age, sex, clinic site and education, we examined adjusted mean cognitive test scores by categories of sleep and RAR exposures. Mean age was 76 years, 58% were female, and 15% were non-white. Higher RA, reflecting a more robust 24-hour RAR, was associated with better cognition on all tests (p for trend <0.05). Reduced SE was related to lower cognitive function (psychomotor performance, global cognition, memory; p<.05). There were no associations with TST and any cognitive measures examined. SE and RAR were variably associated with both global and specific domains of cognition in older men and women. The RA in particular was strongly related to multiple domains of cognition related to AD, and may be useful in identifying individuals at risk. Additional analyses will explore sex differences and longitudinal associations.

SOCIAL PARTICIPATION, LONELINESS, AND CIRCADIAN RHYTHMS OF MIDDLE-AGED AND OLDER ADULTS IN TAIWAN

Abstract Loneliness among middle-aged and older adults is a growing public health concern in the aging society. While social participation is known as a protective factor against loneliness, not all older adults enjoy social participation. The purpose of this study is to investigate the social participation and loneliness characteristics in communities and their association with the demographic data, health-related variables, objective sleep parameters and rest-activity circadian rhythms with a sample of 242 Taiwan community-dwelling middle-aged and older adults aged 45 to 89 years. Loneliness and social participation levels were grouped in different clusters via Two-Step Cluster Analysis. Subsequently, Chi-square test and ANOVA were performed to identify the differences between clusters with relevant variables. Results showed that five social participation-loneliness clusters were grouped: Average(40.1%), Active-Lonely(3.8%), Not Active-Lonely(13.1%),Active -Not Lonely(5.9%),Not Active -Not Lonely(37.1%). Age, employment status, property management, self-perceived health, depression, life satisfaction and relative amplitude were related to clusters. The Active-Not Lonely cluster was older, had a higher retirement percentage, and higher life satisfaction. Compared with the Not Active-Lonely cluster, the Not Active -Not Lonely cluster had more power to manage their property, felt healthier and less depressive. The Active-Lonely cluster had a high percentage of unemployment and felt unhealthier. The Not Active-Lonely cluster had the lowest relative amplitude, which meant they had weaker rest-activity circadian rhythms. Objective sleep parameters were no difference between each cluster. These findings provide the potential benefits of developing appropriate social care programs to reduce loneliness for middle-aged and older adults via objective data.

A biological age biomarker based on circadian rest‐activity rhythms and risk of dementia

AbstractBackgroundCircadian function is altered with aging, leading to changes in the ∼24‐h rhythms of behavior and physiology. Based on circadian rest‐activity rhythms (CRAR), we previously constructed a biological age biomarker to characterize the aging profile of circadian function—circadian age (CircAge)—in older adults (>65 years) and showed its association with risk of Alzheimer’s dementia. Here, we constructed CircAge in middle‐to‐older‐aged adults and tested whether it predicts all‐cause dementia.MethodParticipants from the UK Biobank with valid actigraphy data were studied (n = ∼97,000; 42‐78 years old). We developed a machine‐learning‐based regression model with 23 CRAR features derived from actigraphy (using cosinor, nonparametric, uniform‐phase‐empirical‐mode‐decomposition, and detrended‐fluctuation analyses). The fitting target was chronological age (ChrAge), and the prediction output was defined as CircAge. Model parameters were optimized using cross validation on 47,234 participants not performing shift work and without mental/behavioral or nervous system diseases. The optimized model was applied to all dementia‐free participants with valid CRAR (n = 80,805) to obtain their CircAge.ResultCircAge was 1.03±0.01 years older per one‐year older in ChrAge that explained ∼25% of the variance of CircAge (p<0.0001). Male sex, European ethnicity, or having mental/behavioral/nervous system diseases were associated with a greater CircAge (all p<0.0001). We compared CircAge of current shift workers (n = 6,389) with that of matched non‐shift workers to examine whether CircAge captures CRAR perturbations and found that CircAge of current shift workers was 1.1±0.2 years greater (p<0.0001) than non‐shift workers. We then associated the difference between CircAge and ChrAge (DCC, = CircAge‐ChrAge) to incident all‐cause dementia using a Cox proportional hazards model adjusting for ChrAge, sex, ethnic groups, mental/behavioral diseases, and nervous system diseases. Results showed that greater DCC predicted higher adjusted risk of all‐cause dementia (n = 451): each decade higher DCC corresponding to a 1.10‐fold higher risk (95% CI: 1.02‐1.18; p = 0.009).ConclusionCRAR patterns can be translated into a biological aging biomarker for circadian function (CircAge), and greater CircAge than ChrAge is independently associated with risk of dementia in middle‐to‐older‐aged adults. Future studies are warranted to examine the use of CircAge (and/or in combination with other risk markers) for identifying at‐risk individuals in a clinical setting.

Rest-activity circadian rhythm in hospitalized older adults with mild cognitive impairment in Korea and its relationship with salivary alpha amylase: an exploratory study

Purpose: This study aimed to evaluate the rest-activity circadian rhythm (RAR) using data obtained from wearable actigraph devices in hospitalized older adults with mild cognitive impairment (MCI), and to investigate its relationship with salivary alpha amylase (sAA).Methods: This secondary data analysis used data from the Hospitalized Older Adults’ Cognition and Physical Activity Study. Actigraph data for 3-4 days were analyzed for RAR. RAR indices such as interdaily stability (IS), intradaily variability (IV), activity level during the most active 10-hour period and during the most least active 5-hour period, and relative amplitude (RA) were calculated. Data on sAA collected in the morning and general characteristics, including body mass index (BMI), were analyzed. Results: Data from 92 hospitalized older adults with MCI were analyzed. The IS, IV, RA were 0.23, 0.73, 0.88, respectively. The average level of sAA was 77.02 U/mL, and a higher level of sAA was significantly associated with better IS and RA in the regression analysis, while age, BMI, and cognitive level were not. BMI showed positive correlations with IS and RA. Conclusion: RAR in the hospitalized older adults with MCI was attenuated, showing especially low IS, which implies they failed to maintain regular and repetitive 24-hour RAR. Increased sAA and BMI were associated with robust RAR. Nurses need to pay attention to maintain robust RAR in hospitalized older adults with MCI, and strategies should be developed to improve their RAR.

Mediation and Dose-Response Relationship Among Physical Activity, Daylight Exposure, and Rest-Activity Circadian Rhythm in Patients With Esophageal and Gastric Cancer.

Physical activity and daylight exposure predict rest-activity circadian rhythm (RACR) in patients with cancer. However, whether daylight exposure mediates the relationship between physical activity and RACR and the optimal amounts of physical activity and daylight that benefit RACR remain unclear. This study investigated the mediating role of daylight exposure and determined the dose-response relationship among daylight exposure, physical activity, and RACR in patients with cancer. This cross-sectional exploratory study recruited 319 patients with esophageal and gastric cancer from 2 surgery outpatient departments in Taiwan. Daylight exposure (>500 lux), physical activity (up activity mean), and RACR (midline estimating statistic of rhythm) were measured through actigraphy. Regression was performed, and the receiver operating characteristic curve was plotted. Daylight exposure (>500 lux) partially mediated the relationship between physical activity (up activity mean) and RACR (midline estimating statistic of rhythm). The optimal cutoffs for discriminating between satisfactory and poor RACR were 187.43 counts/min for physical activity (sensitivity, 90.3%; specificity, 84.4%) and 35.71 min/d for daylight exposure (sensitivity, 55.9%; specificity, 78.2%). Participants who engaged in physical activity were more likely to receive daylight exposure and experience improved RACR. The optimal level of daylight exposure and frequency of physical activity that can improve RACR in patients with esophageal and gastric cancer are 36 min/d and 187 counts/min, respectively. Healthcare professionals should encourage patients to engage in exercise or physical activity during the daytime to improve their circadian rhythm.

Circadian disturbances and frailty risk in older adults

Frailty is characterized by diminished resilience to stressor events. It is associated with adverse future health outcomes and impedes healthy aging. The circadian system orchestrates ~24-h rhythms in bodily functions in synchrony with the day-night cycle, and disturbed circadian regulation plays an important role in many age-related health consequences. We investigated prospective associations of circadian disturbances with incident frailty in over 1000 older adults who had been followed annually for up to 16 years. We found that decreased rhythm strength, reduced stability, or increased variation were associated with a higher risk of incident frailty and faster progress of frailty over time. Perturbed circadian rest-activity rhythms may be an early sign or risk factor for frailty in older adults.

Role of age, menopausal status, and symptoms in midlife women: Examination of sleep patterns and rest-activity circadian rhythms

BackgroundMidlife women experience menopausal transition at different ages with a variety of symptoms. This study aimed to identify the effects of age, menopausal status, and symptoms in women on their actigraphy-based sleep patterns and circadian rhythms. MethodsA total of 87 women aged 45–60 from the community and a gynecology clinic in Taiwan who had their sleep and circadian rhythms recorded with a 7-day actigraphy were analyzed. Multiple linear regression was used to estimate the association of age, menopausal status, and symptoms with sleep parameters and circadian rhythms. ResultsA sleep efficiency below 85 % was observed in 46.0 % of women, and those with severe somatic-vegetative or psychological symptoms tended to have problems with sleep latency (β = 0.22 and β = 0.42, respectively) and efficiency (β = −0.26 and β = −0.36, respectively). Women with more severe urogenital symptoms only experienced significantly longer sleep latency (β = 0.33). There was a weak correlation between circadian rhythms and symptoms. Additionally, perimenopausal (β = 0.30 and β = 0.35, respectively) and late postmenopausal (β = 0.67 and β = 0.59, respectively) women had higher relative amplitude and stability in circadian rhythms than premenopausal women. Age had no significant effect on sleep parameters or circadian rhythms. ConclusionsPremenopausal women had the most unstable day-to-day rhythms compared to their peri- and postmenopausal counterparts. Women with higher somatic-vegetative, psychological, and urogenital symptoms showed greater sleep problems. Psychological symptoms (e.g., depression, irritability, anxiety, exhaustion) were the strongest predictors for all sleep parameters. The mechanisms underlying these associations warrant investigation.

54 Sleep and Circadian Rhythms in Premanifest Huntington’s disease: Relationship with Cognition

Objective:Huntington’s disease (HD) is a neurodegenerative disease characterised by motor, psychiatric and cognitive decline. Currently, no treatments have been identified in HD for slowing down cognitive decline or improving cognitive function. We are interested in identifying potentially modifiable factors in HD that can be targeted to improve or maintain cognitive function. Sleep and circadian disruption stand out as possible modifiable targets because sleep and circadian symptoms are common in HD, and such disruptions are known to impact cognition in the general population. Despite some emerging evidence that sleep quality correlates with cognition in manifest HD, whether these same relationships exist in the premanifest period is unknown. Further, whether circadian rhythms relate to cognition in premanifest HD remains open. Therefore, we aimed to determine whether sleep and circadian parameters relate to cognitive performance in premanifest HD.Participants and Methods:To date, we have recruited 27 premanifest HD participants to a two-week remote sleep study. During the study, participants wore an Actiwatch-2 and completed a sleep diary for 14 consecutive days to assess their sleep and rest-activity patterns. Participants also completed online sleep and mood questionnaires and a cognitive assessment using videoconference. We calculated Pearson correlations to examine whether cognitive performance relates to subjective sleep quality, objective sleep parameters and circadian rest-activity rhythms. Thus far, we have analysed data from 15 female participants with premanifest HD (Mage = 43.20, SD = 11.58).Results:Preliminary results indicate that measures of subjective sleep quality, insomnia severity, daytime sleepiness, and fatigue severity in premanifest HD do not correlate with cognitive performance. Increases in objectively measured sleep efficiency, however, strongly correlated with better performance on the Hopkins-Verbal Learning Test-Revised (HVLT-R) immediate (r = 0.562, p < 0.05) and delayed recall trials (r = 0.597, p < 0.05) and the Trail Making Test Part B (TMT-B; r = 0.550, p < 0.05). More time spent awake (i.e., wake after sleep onset) was strongly linked to reduced performance on the TMT-B (r = -0.542, p < 0.05) and Symbol Digit Modalities Test (r = -0.556, p < 0.05). Further, increases in total sleep time were associated with better performance on the HVLT-R immediate (r = 0.682, p < 0.05) and delayed recall trial (r = 0.616, p < 0.05). For our circadian parameters, less fragmented day-today rest-activity rhythms (i.e., higher intra-daily variability) strongly correlated with higher scores on the HVLT-R immediate (r = 0.768, p < 0.001) delayed recall trials (r = 0.7276, p < 0.05) and TMT-B (r = 0.516, p < 0.05), whereas consistent and stable day-to-day rest-activity rhythms (i.e., higher inter-daily stability) was associated with poorer performance on ERT (r = -0.587, p < 0.05).Conclusions:Preliminary results suggest that fragmented sleep, sleep inefficiency, reduced total sleep time, rest-activity rhythm stability and fragmentation relate to poorer cognitive performance in people with premanifest HD. Should analysis of our whole sample confirm these preliminary findings, targeting sleep in HD (e.g., through sleep hygiene and/or psychoeducation) may be a useful strategy to improve or maintain cognition.

Association between Acute Respiratory Distress Syndrome Due to COVID-19 and Long-Term Sleep and Circadian Sleep-Wake Disorders.

Current studies agree on the impact of sleep and circadian rest-activity rhythm alterations in acute respiratory distress syndrome (ARDS) survivors. However, research on the duration of this impact is scarce. In this study, we evaluate the impact of ARDS on the sleep and circadian rest-activity rhythm of COVID-19 survivors twelve months after hospital discharge. This is a prospective study including COVID-19 survivors with and without ARDS during hospitalization. Data was collected four and twelve months after hospital discharge. The interventions included one-week wrist actigraphy and a home sleep apnea test (HSAT), and evaluations were conducted according to the Pittsburgh sleep quality index (PSQI), Epworth sleepiness scale (ESS), and insomnia severity index (ISI). Fifty-two patients were evaluated (ARDS = 31 and non-ARDS = 21); they had a median age of 49.0 [39.0;57.2] years and 53.8% were male. After twelve months, 91.3% presented poor sleep quality, 58.7% presented insomnia, 50% presented daytime somnolence, and 37% presented comorbid insomnia and obstructive sleep apnea (COMISA). No significant improvement was observed in relation to sleep or the circadian rest-activity rhythm between four and twelve months. A tendency of poor sleep quality, insomnia, daytime somnolence, and COMISA was observed. Finally, there was no significant impact on the circadian rest-activity rhythm between four and twelve months or between the groups.

Blue light exposure-dependent improvement in robustness of circadian rest-activity rhythm in aged rats.

The aging effects on circadian rhythms have diverse implications including changes in the pattern of rhythmic expressions, such as a wide fragmentation of the rhythm of rest-activity and decrease in amplitude of activity regulated by the suprachiasmatic nucleus (SCN). The study of blue light on biological aspects has received great current interest due, among some aspects, to its positive effects on psychiatric disorders in humans. This study aims to evaluate the effect of blue light therapy on the SCN functional aspects, through the evaluation of the rest-activity rhythm, in aging rats. For this, 33 sixteen-months-old male Wistar rats underwent continuous records of locomotor activity and were exposed to periods of 6 hours of blue light during the first half of the light phase (Zeitgeber times 0-6) for 14 days. After this, the rats were maintained at 12h:12h light:dark cycle to check the long-term effect of blue light for 14 days. Blue light repeated exposure showed positive effects on the rhythmic variables of locomotor activity in aged rats, particularly the increase in amplitude, elevation of rhythmic robustness, phase advance in acrophase, and greater consolidation of the resting phase. This effect depends on the presence of daily blue light exposure. In conclusion, our results indicate that blue light is a reliable therapy to reduce circadian dysfunctions in aged rats, but other studies assessing how blue light modulates the neural components to modulate this response are still needed.

Sleep behavior and daily activity levels in people with metabolic syndrome: effect of 1 year of metformin treatment.

Impaired sleep and low daily activity levels increase the risk of developing metabolic syndrome (MS). Metformin (MET), an insulin sensitizer drug, is effective in regressing MS and has been recently studied as an adjuvant agent for managing sleep disorders. The present study aimed to assess whether 1,700 mg/day of MET treatment modifies sleep and daily activity levels in people with MS evaluated by Rest-Activity circadian Rhythm (RAR), which is the expression of 24 h of spontaneous activity parameters. A total of 133 subjects with MS, randomized into the MET (n = 65) or placebo (PLA, n = 68) group, underwent a clinical/anthropometric examination and carried out a continuous 7-day actigraphic monitoring to investigate sleep and RAR parameters at baseline and after 1 year of intervention. After 1 year of intervention, 105 subjects were analyzed. The MET group showed greater anthropometric and metabolic improvements compared with placebo, with a significant reduction in weight (p = 0.01), body mass index (p = 0.01), waist circumference (p = 0.03), and glucose (p < 0.001). With regard to sleep parameters, the MET group showed a significant increase in actual sleep time (p = 0.01) and sleep efficiency (p = 0.04) compared with placebo. There were no significant changes reported in the RAR parameters. Our study suggests that MET might be used as an adjuvant treatment for sleep disorders in people with MS.

Circadian rest-activity rhythms and cognitive decline and impairment in older Chinese adults: A multicohort study with prospective follow-up

BackgroundThe associations between rest-activity rhythms and cognitive health are inconclusive. The potential changes in rest-activity rhythms in older people with mild cognitive impairment (MCI) remains unclear. This study aimed to examine the association between rest-activity rhythms and cognitive health across different outcome measures in older Chinese people. MethodsA total of 710 community-dwelling participants (average age 81.1 ± 5.2 years) from two cohort studies. Wrist-worn accelerometer data was used to estimate the circadian rest-activity rhythms at baseline. Cognitive function was assessed and clinical diagnosis was made at baseline and follow-up. The two-way Analysis of Co-variance was used to compare the differences in rest-activity rhythms across participants with cognitively normal, MCI and Alzheimer's disease (AD). Logistic regression models were used to investigate the association between rest-activity rhythms and incidence of cognitive decline and impairment in a 4-year prospective follow-up of cognitively normal individuals. ResultsThere was a progressive trend of lower relative amplitude and higher activity level during the least active 5 h across participants with cognitively normal, MCI and Alzheimer's disease (AD). Among the cognitively normal participants, lower relative amplitude at baseline was associated with a greater risk of cognitive decline (per 1 SD decrease, odds ratio 1.66 [95 %CI 1.13–2.45]) and increased incidence of MCI or AD (per 1 SD decrease, 1.68 [1.12–2.50]). ConclusionsLower relative amplitude could potentially serve as a robust biomarker of cognitive decline and impairment. Further studies could evaluate the potential benefits of interventions associated with rest-activity relative amplitude to prevent or delay the progression of AD.