Sleep variability, health-related practices, and inflammatory markers in a community dwelling sample of older adults

Do Sleep Problems Exacerbate the Mental Health Consequences of Discrimination Among Adults?

OBJECTIVE

An emerging literature suggests that sleep may play an important role in moderating the association between discrimination and mental health problems among adolescents. However, few if any studies have considered this topic among adults. Addressing this knowledge gap, the current study examined multiple sleep parameters as moderating variables in the association between discrimination and mental health problems among adults.

METHODS

Participants were 874 adults residing in small towns and semirural contexts within the Southeastern region of the United States ( Mage = 41 years, SD = 7; 57% female; 31% Black, 69% White; 52% income-to-needs < 2). Sleep duration and night-to-night variability in duration were assessed using wrist actigraphy. Established self-report measures were used to assess global sleep problems, experiences of discrimination, and mental health problems (anxiety, depression, and externalizing symptoms).

RESULTS

Experiences of discrimination were associated with more depression, anxiety, and externalizing problems. Two out of three sleep parameters were found to moderate the effects of discrimination on mental health. The association between discrimination and externalizing problems (but not anxiety or depression) was attenuated among those with less night-to-night variability in sleep duration. The associations between discrimination and anxiety and externalizing problems (but not depression) were attenuated among those with fewer global sleep problems. Less variability in sleep duration and fewer global sleep problems were also directly associated with lower levels of depression, anxiety, and externalizing problems.

CONCLUSIONS

Greater consistency in sleep duration from night-to-night, and fewer overall sleep problems appear to mitigate risk of mental health problems among adults, particularly in contexts where discrimination is prevalent.

Greater sleep variability is associated with higher systemic inflammation in type 2 diabetes

Sleep irregularity and variability have been shown to be detrimental to cardiometabolic health. The present pilot study explored if higher day-to-day sleep irregularity and variability were associated with systemic inflammation, as assessed by high-sensitivity C-reactive protein, in type 2 diabetes. Thirty-five patients with type 2 diabetes (mean age 54.3 years, 54.3% female) who were not shift-workers participated. The presence of diabetic retinopathy was determined. The standard deviation of sleep duration and sleep midpoint across all recorded nights were used to quantify sleep variability and regularity, respectively, assessed by 14-day actigraphy. The presence and severity of sleep apnea were assessed using an overnight home monitor. Low-density lipoprotein, haemoglobin A1C and high-sensitivity C-reactive protein were collected. Multiple regression analysis using natural-log-transformed values was performed to establish an independent association between sleep variability and high-sensitivity C-reactive protein. Twenty-two (62.9%) patients had diabetic retinopathy. The median (interquartile range) of high-sensitivity C-reactive protein was 2.4 (1.4, 4.6) mg L-1. Higher sleep variability was significantly associated with higher high-sensitivity C-reactive protein (r = 0.342, p = 0.044), as was haemoglobin A1C (r = 0.431, p = 0.010) and low-density lipoprotein (r = 0.379, p = 0.025), but not sleep regularity, sleep apnea severity or diabetic retinopathy. Multiple regression analysis showed that higher sleep variability (B = 0.907, p = 0.038) and higher HbA1c (B = 1.519, p = 0.035), but not low-density lipoprotein, contributed to higher high-sensitivity C-reactive protein. In conclusion, higher sleep variability in patients with type 2 diabetes who were not shift-workers was independently associated with higher systemic inflammation, conferring increased cardiovascular risk. Whether sleep interventions to reduce sleep variability can reduce systemic inflammation and improve cardiometabolic health should be investigated.

Objective and Subjective Intraindividual Variability in Sleep: Predisposing Factors and Health Consequences

OBJECTIVE

We investigated the factors that predispose or precipitate greater intraindividual variability (IIV) in sleep. We further examined the potential consequences of IIV on overall sleep quality and health outcomes, including whether these relationships were found in both self-reported and actigraphy-measured sleep IIV.

METHODS

In Study 1, 699 US adults completed a Sleep Intra-Individual Variability Questionnaire and self-reported psychosocial, sleep quality, and health outcomes. In Study 2, 100 university students wore actigraphy and completed psychosocial, sleep, and health surveys at multiple timepoints.

RESULTS

In cross-sectional analyses that controlled for mean sleep duration, predisposing/precipitating factors to greater IIV were being an underrepresented racial/ethnic minority (Study 1: F = 13.95, p < .001; Study 2: F = 7.03, p = .009), having greater stress (Study 2: r values ≥ 0.32, p values ≤ .002) or trait vulnerability to stress (Study 1: r values ≥ 0.15, p values < .001), and showing poorer time management (Study 1: r values ≤ -0.12, p values ≤ .004; Study 2: r values ≤ -0.23, p values ≤ .028). In addition, both studies showed that greater sleep IIV was associated with decreased overall sleep quality, independent of mean sleep duration (Study 1: r values ≥ 0.20, p values < .001; Study 2: r values ≥ 0.33, p values ≤ .001). Concordance across subjective and objective IIV measures was modest ( r values = 0.09-0.35) and similar to concordance observed for subjective-objective mean sleep duration measures.

CONCLUSION

Risk for irregular sleep patterns is increased in specific demographic groups and may be precipitated by, or contribute to, higher stress and time management inefficiencies. Irregular sleep may lead to poor sleep quality and adverse health outcomes, independent of mean sleep duration, underscoring the importance of addressing sleep consistency.

Multidimensional sleep health and diabetic retinopathy: Systematic review and meta-analysis

Diabetic retinopathy (DR) is one of the most prevalent microvascular diabetic complications. Poor sleep health and obstructive sleep apnea (OSA) are risk factors for diabetes and poor glycemic control. Recent studies have suggested associations between poor sleep health/OSA and DR. Furthermore, there have been suggestions of melatonin dysregulation in the context of DR. We conducted a systematic review and meta-analysis exploring the associations between multidimensional sleep health (duration, satisfaction, efficiency, timing/regularity and alertness), OSA and melatonin with DR. Forty-two studies were included. Long, but not short sleep, was significantly associated with DR, OR 1.41 (95%CI 1.21, 1.64). Poor sleep satisfaction was also significantly associated with DR, OR 2.04 (1.41, 2.94). Sleep efficiency and alertness were not associated with DR, while the evidence on timing/regularity was scant. Having OSA was significantly associated with having DR, OR 1.34 (1.07, 1.69). Further, those with DR had significantly lower melatonin/melatonin metabolite levels than those without DR, standardized mean difference -0.94 (-1.44, -0.44). We explored whether treating OSA with continuous positive airway pressure (CPAP) led to improvement in DR (five studies). The results were mixed among studies, but potential benefits were observed in some. This review highlights the association between poor multidimensional sleep health and DR.

Observational study to understand the effect of timing and regularity on sleep metrics and cardiorespiratory parameters using data from a smart bed

Sleep regularity and chronotype can affect health, performance, and overall well-being. This observational study examines how sleep regularity and chronotype affect sleep quality and cardiorespiratory metrics. Data was collected from 1 January 2019 through 30 December 2019 from over 330 000 Sleep Number smart bed users across the United States who opted into this at-home study. A pressure signal from the smart bed reflected bed presence, movements, heart rate (HR), and breathing rate (BR). Participants (mean age: 55.69 years [SD: 14.0]; 51.2% female) were categorized by chronotype (16.8% early; 62.2% intermediate, 20.9% late) and regularity of sleep timing. Participants who were regular sleepers (66.1%) experienced higher percent restful sleep and lower mean HR and BR compared to the 4.8% categorized as irregular sleepers. Regular early-chronotype participants displayed better sleep and cardiorespiratory parameters compared to those with regular late-chronotypes. Significant variations were noted in sleep duration (Cohen's d = 1.54 and 0.88, respectively) and restful sleep (Cohen's d = 1.46 and 0.82, respectively) between early and late chronotypes, particularly within regular and irregular sleep patterns. This study highlights how sleep regularity and chronotype influence sleep quality and cardiorespiratory metrics. Irrespective of chronotype, sleep regularity demonstrated a substantial effect. Further research is necessary to confirm these findings.

Day-to-day deviations in sleep parameters and biological aging: Findings from the NHANES 2011-2014

OBJECTIVES

The majority of the previous research has focused on the impact of average sleep parameters on longevity. In this study, we aimed to investigate the associations of day-to-day deviations in sleep parameters with biological ages among 6052 adults participating in the 2011-2014 waves of the US National Health and Nutrition Examination Survey.

METHODS

Sleep parameters, including sleep duration, efficiency, midpoint, and day-to-day deviations in sleep parameters, including standard deviation of sleep duration (sleep variability), standard deviation of sleep midpoint (sleep irregularity), catch-up sleep, and social jetlag, were obtained from 4 to 7 days of 24-h accelerometer recording. We used physiological data to compute measurements of biological aging according to 3 published algorithms: PhenoAge, Klemera-Doubal method Biological Age, and homeostatic dysregulation.

RESULTS

After adjustment of multiple covariates, we observed that all parameters of day-to-day deviations in sleep were significantly associated with biological aging with larger sleep variability, larger sleep irregularity, more catch-up sleep, and more social jetlag linked with more advanced biological aging. The significant associations of sleep irregularity, catch-up sleep, and social jetlag with biological aging indices remained even after adjustment for sleep duration, efficiency, and midpoint.

CONCLUSION

In this study, we found that day-to-day deviations in sleep parameters are independently associated with biological aging in US general population. Since day-to-day deviation in sleep is a modifiable behavioral factor, our finding suggests that intervention aiming at increasing regularity in sleep patterns may be a novel approach for extending a healthy life span.

The importance of sleep regularity: a consensus statement of the National Sleep Foundation sleep timing and variability panel

OBJECTIVE

To develop and present consensus findings of the National Sleep Foundation sleep timing and variability panel regarding the impact of sleep timing variability on health and performance.

METHODS

The National Sleep Foundation assembled a panel of sleep and circadian experts to evaluate the scientific evidence and conduct a formal consensus and voting procedure. A systematic literature review was conducted using the NIH National Library of Medicine PubMed database, and panelists voted on the appropriateness of 3 questions using a modified Delphi RAND/UCLA Appropriateness Method with 2 rounds of voting.

RESULTS

The literature search and panel review identified 63 full text publications to inform consensus voting. Panelists achieved consensus on each question: (1) is daily regularity in sleep timing important for (a) health or (b) performance? and (2) when sleep is of insufficient duration during the week (or work days), is catch-up sleep on weekends (or non-work days) important for health? Based on the evidence currently available, panelists agreed to an affirmative response to all 3 questions.

CONCLUSIONS

Consistency of sleep onset and offset timing is important for health, safety, and performance. Nonetheless, when insufficient sleep is obtained during the week/work days, weekend/non-work day catch-up sleep may be beneficial.

A National Survey of U.S. Adolescent Sleep Duration, Timing, and Social Jetlag During the COVID-19 Pandemic

OBJECTIVES

To assess changes in duration, timing, and social jetlag in adolescent sleep during the COVID-19 pandemic and evaluate the impact of mood, physical activity, and social interactions on sleep.

STUDY DESIGN

An online survey queried adolescents' sleep before (through retrospective report) and during the initial phase of COVID-19 in May 2020. Adolescents (N = 3,494), 13-19 years old, in the United States (U.S.) answered questions about their current and retrospective (prior to COVID-19) sleep, chronotype, mood, and physical and social activities. Linear regression models were fit for time in bed, reported bed and wake times, and social jetlag during COVID-19, accounting for pre-COVID-19 values.

RESULTS

Total reported time in bed (a proxy for sleep duration) increased on weekdays by an average of 1.3 ± 1.8 hours (p < .001) during COVID-19, compared to retrospective report of time in bed prior to COVID-19. During COVID-19, 81.3% of adolescents reported spending 8 hours or more in bed on weekdays compared to only 53.5% prior to COVID-19. On weekdays, bedtimes were delayed on average by 2.5 hours and wake times by 3.8 hours during COVID-19 compared to prior to COVID-19. On weekends, bedtimes were delayed on average by 1.6 hours and waketimes by 1.5 hours (all p's < 0.001). Social jetlag of >2 hours decreased to 6.3% during COVID-19 compared to 52.1% prior to COVID-19. Anxiety and depression symptoms and a decline in physical activity during COVID-19 were associated with delayed bed and wake times during COVID-19.

CONCLUSIONS

During COVID-19, adolescents reported spending more time in bed, with most adolescents reporting 8 hours of sleep opportunity and more consistent sleep schedules. As schools return to in-person learning, additional research should examine how sleep schedules may change due to school start times and what lessons can be learned from changes that occurred during COVID-19 that promote favorable adolescent sleep.

The Mediating Role of Depression in Association Between Total Sleep Time and Instrumental Activities of Daily Living in China

Objectives: This study aims to investigate the mediating role of depression and the moderating effect of gender in the relationship between total sleep time (TST) and instrumental activities of daily living (IADL) in middle-aged and elderly people (aged 45 or above).

Methods: The data used in this study is from the China Health and Retirement Longitudinal Study (CHARLS), including a total of 10,460 respondents. Associations between TST, IADL, depression, and gender were analyzed using logistic regression and Karlson, Holm, and Breen (KHB) methods.

Results: Short (OR = 1.42, 95% CI = 1.28–1.58 of ≤6 h) and long TST (OR = 1.16, 95% CI = 1.02–1.32 of 8–9 h; OR = 1.35, 95% CI = 1.19–1.54 of &gt;9 h) were both associated with IADL. The mediation effect analyses observed that depression explained 64.80% of the total effect of short TST (≤6 h) and IADL, but was insignificant in long TST (8–9 h and &gt;9 h). Meanwhile, gender has moderating effects on the mediation effect model.

Conclusion: The study suggests that health interventions that focused on the dimensions of TST and depression are crucial for preventing functional disability while accounting for gender differences.

Sleep Irregularity and Subclinical Markers of Cardiovascular Disease: The Multi-Ethnic Study of Atherosclerosis

Background Sleep irregularity has been linked to incident cardiovascular disease. Less is known about associations of sleep regularity with atherosclerosis. We examined cross-sectional associations of actigraphy-assessed sleep duration and sleep timing regularity with subclinical atherosclerosis in the community-based MESA (Multi-Ethnic Study of Atherosclerosis). Methods and Results MESA Sleep Ancillary Study participants (N=2032; mean age, 68.6±9.2 years; 37.9% White) completed 7-day wrist actigraphy. Participants underwent assessments of coronary artery calcium, carotid plaque presence, carotid intima-media thickness, and the ankle-brachial index. Sleep regularity was quantified by the 7-day with-in person SD of sleep duration and sleep onset timing. Relative risk regression models were used to calculate prevalence ratios and 95% CIs. Models are adjusted for demographics, cardiovascular disease risk factors, and other objectively assessed sleep characteristics including obstructive sleep apnea, sleep duration, and sleep fragmentation. After adjustment, compared with participants with more regular sleep durations (SD ≤60 minutes), participants with greater sleep duration irregularity (SD >120 minutes) were more likely to have high coronary artery calcium burden (>300; prevalence ratio, 1.33 [95% CI, 1.03-1.71]) and abnormal ankle-brachial index (<0.9; prevalence ratio, 1.75 [95% CI, 1.03-2.95]). Compared with participants with more regular sleep timing (SD ≤30 minutes), participants with irregular sleep timing (SD >90 minutes) were more likely to have high coronary artery calcium burden (prevalence ratio, 1.39 [95% CI, 1.07-1.82]). Associations persisted after adjustment for cardiovascular disease risk factors and average sleep duration, obstructive sleep apnea, and sleep fragmentation. Conclusions Sleep irregularity, particularly sleep duration irregularity, was associated with several measures of subclinical atherosclerosis. Sleep regularity may be a modifiable target for reducing atherosclerosis risk. Future investigation into cardiovascular risk reduction interventions targeting sleep irregularity may be warranted.

Association of Interleukin-6 and Interleukin-8 with Cognitive Decline in an Asian Memory Clinic Population

BACKGROUND

Neuroinflammation has been postulated to play an important role in cognitive impairment, cognitive decline, and dementia. Inflammatory biomarkers such as interleukin-6 (IL-6) and IL-8 are found to be associated with the neuro-inflammatory process and worse cognitive function. However, it is unknown whether these interleukins are associated with long-term cognitive function.

OBJECTIVE

To investigate the association of baseline IL-6 and IL-8 with cognitive function at baseline as well as its association with cognitive decline over five-year follow-up.

METHODS

387 patients were recruited from an ongoing memory clinic-based study who underwent comprehensive physical, medical, neuropsychological and blood assessments together with brain MRI. IL-6 and IL-8 were measured using LUMINEX assays. The National Institute of Neurological Disorders and Stroke-Canadian Stroke Network neuropsychological battery was used to assess cognitive decline across multiple domains.

RESULTS

Among the 387 (mean age = 72.9 years and 53.7% males) participants, 322 had at least two follow-up assessments and were included in the longitudinal analysis. Negative linear trend associations were found between tertiles of IL-8 with baseline global cognition (p-trend< 0.001), attention (p-trend = 0.005), executive function (p-trend< 0.001), and visuospatial function (p-trend = 0.002) domains. No association was found between baseline IL-8 and cognitive decline. IL-6 was not associated with both baseline and follow-up cognition.

CONCLUSION

IL-8 was associated with worse cognition especially in attention, executive function, and visuospatial function, suggesting the role of neuroinflammation in cognitive impairment. Hence, blood inflammatory biomarkers may be useful indicators in identifying patients at risk of cognitive impairment and warrant consideration for inclusion in treatment trials.

Irregular sleep and cardiometabolic risk: Clinical evidence and mechanisms

Sleep regularity is an essential part of the multidimensional sleep health framework. The phenomenon of irregular sleep patterns is widespread in contemporary lifestyles. This review synthesizes clinical evidence to summarize the measures of sleep regularity and discusses the role of different sleep regularity indicators in developing cardiometabolic diseases (coronary heart disease, hypertension, obesity, and diabetes). Existing literature has proposed several measurements to assess sleep regularity, mainly including the standard deviation (SD) of sleep duration and timing, sleep regularity index (SRI), interdaily stability (IS), and social jetlag (SJL). Evidence on associations between sleep variability and cardiometabolic diseases varies depending on the measure used to characterize variability in sleep. Current studies have identified a robust association between SRI and cardiometabolic diseases. In comparison, the association between other metrics of sleep regularity and cardiometabolic diseases was mixed. Meanwhile, the associations of sleep variability with cardiometabolic diseases differ across the population. SD of sleep characteristics or IS may be more consistently associated with HbA1c in patients with diabetes compared with the general population. The association between SJL and hypertension for patients with diabetes was more accordant than in the general population. Interestingly, the age-stratified association between SJL and metabolic factors was observed in the present studies. Furthermore, the relevant literature was reviewed to generalize the potential mechanisms through which irregular sleep increases cardiometabolic risk, including circadian dysfunction, inflammation, autonomic dysfunction, hypothalamic-pituitary-adrenal (HPA) axis disorder, and gut dysbiosis. Health-related practitioners should give more attention to the role of sleep regularity on human cardiometabolic in the future.

Racial/ethnic variations in inflammatory markers: exploring the role of sleep duration and sleep efficiency

Individuals from minoritized racial/ethnic groups have higher levels of circulating inflammatory markers. However, the mechanisms underlying these differences remain understudied. The objective of this study was to examine racial/ethnic variations in multiple markers of inflammation and whether impaired sleep contributes to these racial/ethnic differences. Nurses from two regional hospitals in Texas (n = 377; 71.62% White; 6.90% Black; 11.14% Hispanic, 10.34% Asian; mean age = 39.46; 91.78% female) completed seven days of sleep diaries and actigraphy to assess mean and variability in total sleep time (TST) and sleep efficiency (SE). On day 7, blood was drawn to assess 4 inflammatory markers: C-reactive protein (CRP), Interleukin-6 (IL-6), Interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α). Results from regression models showed differences in inflammatory markers by race/ethnicity, adjusting for age and gender. The associations between sleep parameters and inflammatory markers also varied by race/ethnicity. Among White nurses, lower mean and greater variability in actigraphy-determined TST and greater variability in diary-determined TST were associated with higher levels of IL-6. Among Black nurses, lower mean diary-determined SE was associated with higher levels of IL-6 and IL-1β. Among Hispanic nurses, greater diary-determined mean TST was associated with higher CRP. Among Asian nurses, greater intraindividual variability in actigraphy-determined SE was associated with lower CRP. Among nurses, we did not find racial/ethnic disparities in levels of inflammation. However, analyses revealed differential relationships between sleep and inflammatory markers by race/ethnicity. Results highlight the importance of using a within-group approach to understand predictors of inflammatory markers.

Characterizing Patterns of Nurses' Daily Sleep Health: a Latent Profile Analysis

BACKGROUND

Nursing is a demanding occupation characterized by dramatic sleep disruptions. Yet most studies on nurses' sleep treat sleep disturbances as a homogenous construct and do not use daily measures to address recall biases. Using person-centered analyses, we examined heterogeneity in nurses' daily sleep patterns in relation to psychological and physical health.

METHODS

Nurses (N = 392; 92% female, mean age = 39.54 years) completed 14 daily sleep diaries to assess sleep duration, efficiency, quality, and nightmare severity, as well as measures of psychological functioning and a blood draw to assess inflammatory markers interleukin-6 (IL-6) and C-reactive protein (CRP). Using recommended fit indices and a 3-step approach, latent profile analysis was used to identify the best-fitting class solution.

RESULTS

The best-fitting solution suggested three classes: (1) "Poor Overall Sleep" (11.2%), (2) "Nightmares Only" (8.4%), (3) "Good Overall Sleep" (80.4%). Compared to nurses in the Good Overall Sleep class, nurses in the Poor Overall Sleep or Nightmares Only classes were more likely to be shift workers and had greater stress, PTSD symptoms, depression, anxiety, and insomnia severity. In multivariate models, every one-unit increase in insomnia severity and IL-6 was associated with a 33% and a 21% increase in the odds of being in the Poor Overall Sleep compared to the Good Overall Sleep class, respectively.

CONCLUSION

Nurses with more severe and diverse sleep disturbances experience worse health and may be in greatest need of sleep-related and other clinical interventions.

Sleep-onset time variability and sleep characteristics on weekday and weekend nights in patients with COPD

Objective:

To evaluate sleep-onset time variability, as well as sleep characteristics on weekday and weekend nights, in individuals with moderate-to-severe COPD.

Methods:

Sleep was objectively assessed by an activity/sleep monitor for seven consecutive nights in individuals with COPD. For analysis, individuals were divided into two groups according to sleep-onset time variability results, characterized by intrasubject standard deviation of sleep-onset time (SOT_V) ≥ 60 min or < 60 min.

Results:

The sample comprised 55 individuals (28 males; mean age = 66 ± 8 years; and median FEV₁ % of predicted = 55 [38-62]). When compared with the SOT_V<60min group (n = 24), the SOT_V≥60min group (n = 31) presented shorter total sleep time (5.1 ± 1.3 h vs. 6.0 ± 1.3 h; p = 0.006), lower sleep efficiency (73 ± 12% vs. 65 ± 13%; p = 0.030), longer wake time after sleep onset (155 ± 66 min vs. 115 ± 52 min; p = 0.023), longer duration of wake bouts (19 [16-28] min vs. 16 [13-22] min; p = 0.025), and higher number of steps at night (143 [104-213] vs. 80 [59-135]; p = 0.002). In general, sleep characteristics were poor regardless of the day of the week, the only significant difference being that the participants woke up about 30 min later on weekends than on weekdays (p = 0.013).

Conclusions:

Sleep-onset time varied over 1 h in a standard week in the majority of individuals with COPD in this sample, and a more irregular sleep onset indicated poor sleep quality both on weekdays and weekends. Sleep hygiene guidance could benefit these individuals if it is integrated with their health care.

Sleep disruption induces activation of inflammation and heightens risk for infectious disease: Role of impairments in thermoregulation and elevated ambient temperature

Thermoregulation and sleep are tightly coordinated, with evidence that impairments in thermoregulation as well as increases in ambient temperature increase the risk of sleep disturbance. As a period of rest and low demand for metabolic resources, sleep functions to support host responses to prior immunological challenges. In addition by priming the innate immune response, sleep prepares the body for injury or infection which might occur the following day. However when sleep is disrupted, this phasic organization between nocturnal sleep and the immune system becomes misaligned, cellular and genomic markers of inflammation are activated, and increases of proinflammatory cytokines shift from the nighttime to the day. Moreover, when sleep disturbance is perpetuated due to thermal factors such as elevated ambient temperature, the beneficial crosstalk between sleep and immune system becomes further imbalanced. Elevations in proinflammatory cytokines have reciprocal effects and induce sleep fragmentation with decreases in sleep efficiency, decreases in deep sleep, and increases in rapid eye movement sleep, further fomenting inflammation and inflammatory disease risk. Under these conditions, sleep disturbance has additional potent effects to decrease adaptive immune response, impair vaccine responses, and increase vulnerability to infectious disease. Behavioral interventions effectively treat insomnia and reverse systemic and cellular inflammation. Further, insomnia treatment redirects the misaligned inflammatory- and adaptive immune transcriptional profiles with the potential to mitigate risk of inflammation-related cardiovascular, neurodegenerative, and mental health diseases, as well as susceptibility to infectious disease.

Sleep optimization to improve glycemic control in adults with type 1 diabetes: study protocol for a randomized controlled parallel intervention trial

BACKGROUND

Despite improvements in treatment regimens and technology, less than 20% of adults with type 1 diabetes (T1D) achieve glycemic targets. Sleep is increasingly recognized as a potentially modifiable target for improving glycemic control. Diabetes distress, poor self-management behaviors, and reduced quality of life have also been linked to sleep variability and insufficient sleep duration. A significant gap of knowledge exists regarding interventions to improve sleep and the effects of sleep optimization on glycemic control in T1D. The purpose of this study is to determine the efficacy of a T1D-specific sleep optimization intervention (Sleep-Opt) on the primary outcomes of sleep variability, sleep duration, and glycemic control (A1C); other glycemic parameters (glycemic variability, time-in-range [TIR]); diabetes distress; self-management behaviors; quality of life; and other patient-reported outcomes in adults with T1D and habitual increased sleep variability or short sleep duration.

METHODS

A randomized controlled parallel-arm study will be employed in 120 adults (aged 18 to 65 years) with T1D. Participants will be screened for habitual sleep variability (> 1 h/week) or insufficient sleep duration (< 6.5 h per night). Eligible subjects will be randomized to the Sleep-Opt intervention group or healthy living attention control group for 12 weeks. A 1-week run-in period is planned, with baseline measures of sleep by actigraphy (sleep variability and duration), glycemia (A1C and related glycemic measures: glycemic variability and TIR using continuous glucose monitoring), and other secondary outcomes: diabetes distress, self-management behaviors, quality of life, and additional patient-reported outcomes. Sleep-Opt is a technology-assisted behavioral sleep intervention that we recently developed that leverages the rapidly increasing public interest in sleep tracking. Our behavioral intervention employs four elements: a wearable sleep tracker, didactic content, an interactive smartphone application, and brief telephone counseling. The attention control group will participate in a healthy living information program. Baseline measures will be repeated at midpoint, program completion, and post-program (weeks 6, 12, and 24, respectively) to determine differences between the two groups and sustainability of the intervention.

DISCUSSION

A better understanding of strategies to improve sleep in persons with T1D has the potential to be an important component of diabetes.

TRIAL REGISTRATION

Clinical Trial Registration: NCT04506151 .

The Effects of Objective Push-type Sleep Feedback on Habitual Sleep Behavior and Momentary Symptoms in Daily Life: Mobile Health Intervention Trial using a Healthcare IoT System (Preprint)

Background

Sleep is beneficial for physical and mental health. Several mobile and wearable sleep-tracking devices have been developed, and personalized sleep feedback is the most common functionality among these devices. To date, no study has implemented an objective push-type feedback message and investigated the characteristics of habitual sleep behavior and diurnal symptoms when receiving sleep feedback.

Objective

We conducted a mobile health intervention trial to examine whether sending objective push-type sleep feedback changes the self-reported mood, physical symptoms, and sleep behavior of Japanese office workers.

Methods

In total, 31 office workers (mean age 42.3, SD 7.9 years; male-to-female ratio 21:10) participated in a 2-arm intervention trial from November 30 to December 19, 2020. The participants were instructed to indicate their momentary mood and physical symptoms (depressive mood, anxiety, stress, sleepiness, fatigue, and neck and shoulder stiffness) 5 times a day using a smartphone app. In addition, daily work performance was rated once a day after work. They were randomly assigned to either a feedback or control group, wherein they did or did not receive messages about their sleep status on the app every morning, respectively. All participants wore activity monitors on their nondominant wrists, through which objective sleep data were registered on the web on a server. On the basis of the estimated sleep data on the server, personalized sleep feedback messages were generated and sent to the participants in the feedback group using the app. These processes were fully automated.

Results

Using hierarchical statistical models, we examined the differences in the statistical properties of sleep variables (sleep duration and midpoint of sleep) and daily work performance over the trial period. Group differences in the diurnal slopes for mood and physical symptoms were examined using a linear mixed effect model. We found a significant group difference among within-individual residuals at the midpoint of sleep (expected a posteriori for the difference: −15, 95% credible interval −26 to −4 min), suggesting more stable sleep timing in the feedback group. However, there were no significant group differences in daily work performance. We also found significant group differences in the diurnal slopes for sleepiness (P<.001), fatigue (P=.002), and neck and shoulder stiffness (P<.001), which was largely due to better scores in the feedback group at wake-up time relative to those in the control group.

Conclusions

This is the first mobile health study to demonstrate that objective push-type sleep feedback improves sleep timing of and physical symptoms in healthy office workers. Future research should incorporate specific behavioral instructions intended to improve sleep habits and examine the effectiveness of these instructions.

The brain structure and genetic mechanisms underlying the nonlinear association between sleep duration, cognition and mental health

Sleep duration, psychiatric disorders and dementias are closely interconnected in older adults. However, the underlying genetic mechanisms and brain structural changes are unknown. Using data from the UK Biobank for participants primarily of European ancestry aged 38-73 years, including 94% white people, we identified a nonlinear association between sleep, with approximately 7 h as the optimal sleep duration, and genetic and cognitive factors, brain structure, and mental health as key measures. The brain regions most significantly underlying this interconnection included the precentral cortex, the lateral orbitofrontal cortex and the hippocampus. Longitudinal analysis revealed that both insufficient and excessive sleep duration were significantly associated with a decline in cognition on follow up. Furthermore, mediation analysis and structural equation modeling identified a unified model incorporating polygenic risk score (PRS), sleep, brain structure, cognition and mental health. This indicates that possible genetic mechanisms and brain structural changes may underlie the nonlinear relationship between sleep duration and cognition and mental health.

Efficacy and safety of tuina for senile insomnia: A protocol for systematic review and meta-analysis

BACKGROUND

Insomnia is a common diseases of the elderly, tuina is a widely used treatment. At present, there is a lack of supportive evidence on efficacy and safety of tuina for senile insomnia. The purpose of this systematic review is to assess the effectiveness and safety of tuina therapy in the treatment of senile insomnia.

METHODS

Literature on tuina for senile insomnia in the PubMed, EMBASE, Web of Science, Cochrane, China National Knowledge Infrastructure Database, Wanfang, Chinese Scientific and Journal Database, Japanese medical database, Korean Robotics Institute Summer Scholars, and Thai-Journal Citation Index Center will be conducted to search from the creation of these databases. We will search the databases from the beginning to January 2022. The primary outcome was the Pittsburgh Sleep Quality Index score, and the secondary outcomes included clinical efficacy and safety. RevMan 5.4.1 will be used for the meta-analysis.

RESULTS

This study aimed to will prove the effectiveness and safety of tuina therapy for the treatment of insomnia in the elderly.

CONCLUSION

This study provides up-to-date evidence of the effectiveness and safety of tuina for the treatment of senile insomnia.

INPLASY REGISTRATION NUMBER

INPLASY2021110063.

ETHICS AND COMMUNICATION

This systematic review will evaluate the effectiveness and safety of massage therapy for insomnia in the elderly population. As all the included data have been published, systematic reviews do not require ethical approval.

Science Forum: Sex differences and sex bias in human circadian and sleep physiology research

Growing evidence shows that sex differences impact many facets of human biology. Here we review and discuss the impact of sex on human circadian and sleep physiology, and we uncover a data gap in the field investigating the non-visual effects of light in humans. A virtual workshop on the biomedical implications of sex differences in sleep and circadian physiology then led to the following imperatives for future research: (1) design research to be inclusive and accessible, (2) implement recruitment strategies that lead to a sex-balanced sample, (3) use data visualization to grasp the effect of sex, (4) implement statistical analyses that include sex as a factor and/or perform group analyses by sex, where possible, (5) make participant-level data open and available to facilitate future meta-analytic efforts.

Intraindividual variability in sleep among people with insomnia and its relationship with sleep, health and lifestyle factors: an exploratory study

OBJECTIVE

To explore associations between intraindividual variability (IIV) in sleep patterns and sleep problems, lifestyle factors, and mental and physical health in individuals with chronic insomnia.

METHODS

Cross-sectional study of 1720 adults with chronic insomnia (67.8% female, mean age = 44.5) who completed online self-report questionnaires and kept a sleep diary (for at least 10 out of 14 days). Linear regression analyses examined IIV in sleep patterns as independent variables, and sleep problems, lifestyle factors, and mental and physical health outcomes as dependent variables. Analysis of each sleep variable was separately adjusted for the mean value of the corresponding variable and for selected background factors.

RESULTS

IIV in sleep variables was significantly and positively associated with scores on the Insomnia Severity Index (ISI), dysfunctional beliefs and attitudes about sleep (DBAS-16), the Chalder Fatigue Scale (CFQ), body mass index (BMI) and alcohol consumption (AUDIT-C) at study entry. The association between IIV and mental health outcomes (ie the Hospital Anxiety and Depression Scale [HADS] and subjectively reported mental health status [SF-12 Mental health]) were not significant. IIV was associated with higher (ie more positively rated) mean level of sleep quality.

CONCLUSION

IIV of sleep patterns may be a useful construct for understanding subjective experiences of sleep problems, fatigue and health in people with chronic insomnia. Our findings support notions suggesting that IIV offers additional insights beyond those offered by studying mean values alone; however, discordant findings regarding sleep quality highlight the need for further studies to examine the consequences of IIV.

A Brewed Awakening: Neuropsychiatric Effects of Caffeine in Older Adults

This article provides a current review of the literature examining caffeine use in older adults. Caffeine use is prevalent among older adults; thus, providers need to be aware of the prevalence and diagnostic criteria of caffeine use disorder versus nonproblematic use. The relationship between caffeine and various neuropsychiatric disorders, including Parkinson's disease, Alzheimer's disease, insomnia, and late-life depression, is reviewed. The neurobiological effects of caffeine are described, along with clinically relevant interactions between caffeine and common psychotropic medications.

Suicidal ideation and suicide attempts: associations with sleep duration, insomnia, and inflammation

BACKGROUND

Sleep disturbance has been consistently identified as an independent contributor to suicide risk. Inflammation has emerged as a potential mechanism linked to both sleep disturbance and suicide risk. This study tested associations between sleep duration, insomnia, and inflammation on suicidal ideation (SI) and history of a suicide attempt (SA).

METHODS

Participants included 2329 adults with current or remitted depression and/or anxiety enrolled in the Netherlands Study of Depression and Anxiety. Sleep duration, insomnia, past week SI, and SA were assessed with self-report measures. Plasma levels of C-reactive protein, interleukin-6, and tumor necrosis factor-α were obtained.

RESULTS

Short sleep duration (⩽6 h) compared to normal sleep duration (7-9 h) was associated with reporting a prior SA, adjusting for covariates [adjusted odds ratio (AOR) 1.68, 95% CI 1.13-2.51]. A higher likelihood of SI during the past week was observed for participants with long sleep duration (⩾10 h) compared to normal sleep duration (AOR 2.22, 95% CI 1.02-4.82), more insomnia symptoms (AOR 1.44, 95% CI 1.14-1.83), and higher IL-6 (AOR 1.31, 95% CI 1.02-1.68). Mediation analyses indicated that the association between long sleep duration and SI was partially explained by IL-6 (AOR 1.02, 95% CI 1.00-1.05).

CONCLUSIONS

These findings from a large sample of adults with depression and/or anxiety provide evidence that both short and long sleep duration, insomnia symptoms, and IL-6 are associated with the indicators of suicide risk. Furthermore, the association between long sleep duration and SI may operate through IL-6.

The Sleep Regularity Questionnaire: development and initial validation

BACKGROUND/OBJECTIVE

Sleep is a critically important behavior which influences diverse aspects of health, functioning, and longevity. An increasing literature suggests the importance of sleep regularity, also referred to as sleep inconsistency, sleep variability, or intraindividual variability in sleep. Given there is no brief, subjective measure of sleep regularity, the purpose of this study was to develop the Sleep Regularity Questionnaire (SRQ) and to begin the process of examining its psychometric properties using a construct-validation approach.

PARTICIPANTS/METHODS

In an online study of sleep and health, participants (n = 3249; M_age (SD) = 42.77 (16.73); 48.5% female; 77.3% white) completed the in-development SRQ, as well as the Insomnia Severity Index and the Pittsburgh Sleep Quality Index.

RESULTS

An exploratory factor analysis followed by a confirmatory factor analysis revealed a two factor structure, represented by circadian regularity and sleep continuity regularity, with good model fit indices (X² = 50.9, df = 7, p < 0.001; RMSEA = 0.06; CFI = 0.99; NFI = 0.99; IFI = 0.99; TLI = 0.98). Test-retest reliability, as well as concurrent, convergent and incremental validity were examined, with promising results.

CONCLUSIONS

Preliminary psychometrics suggest that the SRQ is a valid and stable instrument for the assessment of sleep regularity in adults that is related to, but distinct from, other established sleep constructs. Future research will benefit from assessing the validity of the SRQ in various clinical samples and how it compares to measures of sleep regularity calculated from prospective daily assessments.

Gender differences in nighttime sleep patterns and variability across the adult lifespan: a global-scale wearables study

STUDY OBJECTIVES

Previous research on sleep patterns across the lifespan have largely been limited to self-report measures and constrained to certain geographic regions. Using a global sleep dataset of in situ observations from wearable activity trackers, we examine how sleep duration, timing, misalignment, and variability develop with age and vary by gender and BMI for nonshift workers.

METHODS

We analyze 11.14 million nights from 69,650 adult nonshift workers aged 19-67 from 47 countries. We use mixed effects models to examine age-related trends in naturalistic sleep patterns and assess gender and BMI differences in these trends while controlling for user and country-level variation.

RESULTS

Our results confirm that sleep duration decreases, the prevalence of nighttime awakenings increases, while sleep onset and offset advance to become earlier with age. Although men tend to sleep less than women across the lifespan, nighttime awakenings are more prevalent for women, with the greatest disparity found from early to middle adulthood, a life stage associated with child-rearing. Sleep onset and duration variability are nearly fixed across the lifespan with higher values on weekends than weekdays. Sleep offset variability declines relatively rapidly through early adulthood until age 35-39, then plateaus on weekdays, but continues to decrease on weekends. The weekend-weekday contrast in sleep patterns changes as people age with small to negligible differences between genders.

CONCLUSIONS

A massive dataset generated by pervasive consumer wearable devices confirms age-related changes in sleep and affirms that there are both persistent and life-stage dependent differences in sleep patterns between genders.

Measuring sleep regularity: Theoretical properties and practical usage of existing metrics

STUDY OBJECTIVES

Sleep regularity predicts many health-related outcomes. Currently, however, there is no systematic approach to measuring sleep regularity. Traditionally, metrics have assessed deviations in sleep patterns from an individual's average. Traditional metrics include intra-individual standard deviation (StDev), Interdaily Stability (IS), and Social Jet Lag (SJL). Two metrics were recently proposed that instead measure variability between consecutive days: Composite Phase Deviation (CPD) and Sleep Regularity Index (SRI). Using large-scale simulations, we investigated the theoretical properties of these five metrics.

METHODS

Multiple sleep-wake patterns were systematically simulated, including variability in daily sleep timing and/or duration. Average estimates and 95% confidence intervals were calculated for six scenarios that affect measurement of sleep regularity: 'scrambling' the order of days; daily vs. weekly variation; naps; awakenings; 'all-nighters'; and length of study.

RESULTS

SJL measured weekly but not daily changes. Scrambling did not affect StDev or IS, but did affect CPD and SRI; these metrics, therefore, measure sleep regularity on multi-day and day-to-day timescales, respectively. StDev and CPD did not capture sleep fragmentation. IS and SRI behaved similarly in response to naps and awakenings but differed markedly for all-nighters. StDev and IS required over a week of sleep-wake data for unbiased estimates, whereas CPD and SRI required larger sample sizes to detect group differences.

CONCLUSIONS

Deciding which sleep regularity metric is most appropriate for a given study depends on a combination of the type of data gathered, the study length and sample size, and which aspects of sleep regularity are most pertinent to the research question.

Links between objective sleep and sleep variability measures and inflammatory markers in adults with bipolar disorder

Premature mortality and increased physical comorbidity associated with bipolar disorder (BD) may be related to accelerated biological aging. Sleep disturbances and inflammation may be key mechanisms underlying accelerated aging in adults with BD. To our knowledge, these relationships have not been examined rigorously. This cross-sectional study included 50 adults with BD and 73 age- and sex-comparable non-psychiatric comparison (NC) subjects, age 26-65 years. Participants were assessed with wrist-worn actigraphy for total sleep time (TST), percent sleep (PS), and bed/wake times for 7 consecutive nights as well as completing scales for subjective sleep quality. Within-individual variability in sleep measures included intra-individual standard deviation (iSD) and atypicality of one evening's sleep. Blood-based inflammatory biomarkers included interleukin (IL)-6, C-reactive protein (CRP), and tumor necrosis factor-alpha (TNF-α). Linear regression analyses tested relationships of mean and iSD sleep variables with inflammatory marker levels; time-lagged analyses tested the influence of the previous evening's sleep on inflammation. BD participants had worse subjective sleep quality, as well as greater TST iSD and wake time iSD compared to the NC group. In all participants, higher TST iSD and lower mean PS were associated with higher IL-6 levels (p = 0.04, η_p² = 0.042; p = 0.05, η_p² = 0.039, respectively). Lower mean PS was associated with higher CRP levels (p = 0.05, η_p² = 0.039). Atypicality of the previous night's TST predicted next day IL-6 levels (p = 0.05, η_p² = 0.04). All of these relationships were present in both BD and NC groups and remained significant even after controlling for sleep medications. Overall, sleep measures and their variability may influence inflammatory markers in all adults. Thus, sleep may be linked to the inflammatory processes believed to underlie accelerated aging in BD.

Rest-activity rhythms in emerging adults: implications for cardiometabolic health

Emerging adulthood (18-25 years) represents a window of opportunity to modify the trajectory of cardiometabolic disease risk into older adulthood. Not known is the extent to which rest-activity rhythms (RAR) may be related to biomarkers of cardiometabolic health in this population. In this cross-sectional, observational study, 52 healthy emerging adults wore wrist accelerometers (14 consecutive days; 24 h/day) for assessment of nonparametric RAR metrics, including interdaily stability (IS; day-to-day RAR consistency), intradaily variability (IV; within-day RAR fragmentation), and relative amplitude (RA; robustness of RAR), as well as autocorrelation (correlation of rest/activity levels at 24-h lag-times). Cardiometabolic biomarkers, including body mass index (BMI), body fat percentage, blood pressure (BP), fasting lipids, glucose, and C-reactive protein (CRP) were assessed. Additional measures including physical activity, sleep duration, and habitual caffeine and alcohol consumption were also evaluated. A series of multivariable regression models of cardiometabolic biomarkers were used to quantify associations with RAR metrics. On average, participants were 20 ± 1 years of age (21 males, 31 females), non-obese, and non-hypertensive. All were nonsmokers and free of major diseases or conditions. In separate models, which adjusted for sex, BMI, moderate-vigorous physical activity, sleep duration, caffeine, and alcohol consumption, IS was inversely associated with total cholesterol (p ≤ 0.01) and non-HDL cholesterol (p < .05), IV was positively associated with CRP (p < .05), and autocorrelation was inversely associated with total cholesterol (p < .05) and CRP (p < .05). Conversely, associations between RA and cardiometabolic biomarkers were nonsignificant after adjustment for BMI, alcohol, and caffeine consumption. In conclusion, RAR metrics, namely, a higher IS, lower IV, and higher autocorrelation, emerged as novel biomarkers associated with more favorable indices of cardiometabolic health in this sample of apparently healthy emerging adults.

Linking discrimination and sleep with biomarker profiles: An investigation in the MIDUS study

Self-reported experiences of discrimination and sleep dysfunction have both been shown to adversely impact biological functioning; however, few studies have examined how they are jointly associated with health. The current study draws from two samples of the Midlife in the United States (MIDUS) data (n ​= ​617 participants; 59.8% female; 72.3% White and 27.7% African American; Age: Mean ​= ​52.6, SD ​= ​12.22) to identify profiles of sleep (duration, variability, onset latency, wake after sleep onset, naps) and discrimination (everyday, lifetime, impact). Associations with latent profiles of biomarkers of inflammation (CRP, fibrinogen, IL-6) and endocrine stress (cortisol, epinephrine, norepinephrine) were examined. Three profiles were identified for sleep/discrimination (good, fair, poor) and for biomarkers (average, high inflammation, high neuroendocrine). Chi-square analyses indicated that adults in the good sleep/low discrimination profile were more likely to be in the average biomarker profile but less likely to be in the high inflammation profile. Adults in the fair sleep/moderate discrimination risk profile were more likely to be in the high inflammation profile. Adults in the poor sleep/high discrimination risk profile were less likely to be in the average biomarker profile but more likely to be in the high inflammation profile. The current study identified configurations of sleep and discrimination among midlife adults which were associated with profiles of biological risk. The findings provide implications for identifying individuals who may be at increased risk of developing stress-related tertiary outcomes of morbidity and disease.

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Evidence for distinct profiles of sleep/discrimination among Black and White adults.

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Riskier sleep/discrimination profiles are associated with riskier biomarker profiles.

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Black adults were more likely to be in the riskier sleep and biomarker profiles.

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Study links sleep and discrimination to inflammatory and endocrine biomarkers.

Sleep and Inflammation During Adolescents' Transition to Young Adulthood

PURPOSE

This study investigated the extent to which multiple sleep dimensions are associated with inflammation during adolescents' transition to young adulthood, a developmental period when sleep difficulties and systemic inflammation levels are on the rise. Additionally, the moderating roles of socioeconomic status (SES) and ethnicity were explored.

METHODS

A total of 350 Asian American, Latino, and European American youth participated at two-year intervals in wave 1 (n = 316, M_age = 16.40), wave 2 (n = 248 including 34 new participants to refresh the sample, M_age = 18.31), and wave 3 (n = 180, M_age = 20.29). Sleep duration (weekday and weekend) and variability in duration (nightly and weekday/weekend) were obtained from eight nights of wrist actigraphy. Subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index. Levels of C-reactive protein (CRP), a biomarker of systemic inflammation, were assayed from dried blood spots obtained from finger pricks.

RESULTS

Multilevel models demonstrated that greater weekday/weekend sleep variability and worse sleep quality were associated with higher CRP; shorter weekend duration was associated with higher CRP only at younger ages. Shorter weekday duration was associated with higher CRP only among high-SES youth, whereas greater nightly variability was associated with higher CRP only among European American youth.

CONCLUSIONS

Aspects of poor sleep may contribute to the rise of CRP during adolescents' transition to young adulthood, especially in earlier years. In addition, some sleep-CRP associations may vary as a function of youth's SES and ethnicity.

Sleep Inconsistency and Markers of Inflammation

Objective: Poor sleep is associated with higher levels of inflammatory biomarkers. Conventionally, higher average time awake, lower average time asleep, and lower sleep efficiency define poor sleep. Recent research suggests that, in addition to average sleep, sleep inconsistency is an important indicator of sleep dysfunction. The current study sought to extend our knowledge of the relationship between sleep and inflammation through an examination of sleep inconsistency and inflammatory biomarkers. Methods: Secondary analyses of the Survey of Midlife in the United States (MIDUS) sleep study were conducted. Five hundred thirty-three individuals completed nightly sleep diaries, actigraphy, and underwent a blood draw for the inflammatory biomarkers C-reactive protein, interleukin-6, and fibrinogen. Sleep inconsistency was derived from 7 consecutive nights of assessment and was operationalized as nightly fluctuations in the following variables: terminal wakefulness, number of awakenings, time in bed, sleep onset latency, and wake after sleep onset. Structural equation modeling was used to examine the influence of a latent average sleep and a latent sleep inconsistency variable on a latent inflammation variable. Models were subsequently adjusted for age, sex, BMI, health, and medication. Stratified models by sex were also analyzed. Results: The average sleep model would not converge. The sleep inconsistency model fit the data well. A significant positive association between the latent factors sleep inconsistency and inflammation was observed (β = 10.18, SE = 4.40, p = 0.021), suggesting inconsistent sleep is associated with higher levels of inflammatory biomarkers. When stratified by sex, the association between the latent sleep inconsistency factor and inflammation was significant for women (β = 1.93, SE = 0.82, p = 0.018), but not men (β = 0.20, SE = 0.35, p = 0.566). The association between sleep inconsistency and inflammation weakened following multivariate adjustment (β = 6.23, SE = 3.71, p = 0.093). Conclusions: Inconsistent sleep may be an associated feature of inflammatory dysfunction, especially in women. Future studies should build upon this preliminary work and examine these associations longitudinally and through treatment trials.

Intraindividual Variability in Sleep and Levels of Systemic Inflammation in Nurses

OBJECTIVE

Disturbed sleep is common among nurses and is associated with morbidity and mortality. Inflammation may be one mechanism linking sleep and disease. However, most studies rely on retrospective questionnaires to assess sleep, which fail to account for night-to-night fluctuations in sleep across time (i.e., intraindividual variability [IIV]). We examined prospective associations between mean and IIV in sleep with inflammation markers in nurses.

METHODS

Participants were 392 nurses (mean age = 39.54 years, 92% female, 23% night-shift working) who completed 7 days of sleep diaries and actigraphy to assess mean and IIV in total sleep time and sleep efficiency. Blood was drawn on day 7 to assess inflammation markers C-reactive protein, interleukin (IL)-6, tumor necrosis factor α, and IL-1β.

RESULTS

Greater IIV in total sleep time-measured via both actigraphy and sleep diary-was associated with higher IL-6 (actigraphy: b = 0.05, p = .046, sr = 0.01; diary: b = 0.04, p = .030, sr = 0.01) and IL-1β (actigraphy: b = 0.12, p = .008, sr = 0.02; diary: b = 0.09, p = .025, sr = 0.01), but not C-reactive protein or tumor necrosis factor α. IIV in actigraphy- and sleep diary-determined sleep efficiency was not associated with inflammation biomarkers, nor were any mean sleep variables. Shift work did not moderate any associations.

CONCLUSIONS

Nurses with more variable sleep durations had elevated levels of inflammation, which may increase risk for development of inflammatory-related diseases. Research should investigate how sleep regularization may change levels of inflammation and improve health.

Sleep disturbances in bereavement: A systematic review

Severe, persistent and disabling grief occurs among a sizable minority experiencing bereavement, with diagnostic manuals newly including complicated grief (CG) disorders. Sleep disturbances/disorders have been established as worsening affective and stress-related conditions. However, the role of sleep difficulties in bereavement and CG has not received similar scientific attention. We therefore conducted a systematic review with narrative syntheses on this topic to clarify the role of sleep in bereavement (PROSPERO: CRD42018093145). We searched PubMed, Web of Science and PsychInfo for peer-reviewed English-language articles including (at least one) bereaved sample and sleep disturbance measure. We identified 85 articles on 12.294 participants. We answered seven pre-defined research questions demonstrating: high prevalence of sleep disturbances in bereavement; positive associations of grief intensity with sleep difficulties; preliminary indications of risk factors of post-loss sleep disturbance; higher prevalence of sleep disturbances in CG, enhanced by psychiatric comorbidity (i.e., depression); and initial evidence of causal relationships between (complicated) grief and sleep. Grief therapy partly improves sleep difficulties, yet no intervention studies have specifically targeted sleep problems in bereaved persons. Causal relationships between sleep and grief require further examination in intensive longitudinal investigations, including randomized trials, thereby clarifying whether treating sleep problems enhances CG treatment effects.

Sleep Disturbance in Early Pregnancy, but Not Inflammatory Cytokines, May Increase Risk for Adverse Pregnancy Outcomes

BACKGROUND

It is unclear whether subjective or objective measures of sleep during pregnancy are more pertinent to pregnancy outcomes. Moreover, it is unclear as to whether subjective indices (i.e., those likely influenced by psychological thoughts and emotions) are more likely than objective measures to modify inflammatory cytokines.

METHOD

Subjective and objective measures of sleep were collected from 166 pregnant women. Sleep data, both aggregate and variability measures, from diary and actigraphy, were ascertained for three 2-week periods during early gestation (10-20 weeks). A fasting morning blood sample was assayed for the cytokines (IL-6, IFN-γ, and TNF-α). Sleep, stress, and depression questionnaires were also collected. Repeated measures ANOVAs, regression models, and independent t tests were used to analyze the data.

RESULTS

Diary-assessed total sleep time (p < .05) and actigraphy-assessed sleep latency (p = .05) were negatively associated with gestational age. Variability in actigraphy-assessed sleep latency (p < .01) was negatively associated with infant weight. None of the cytokines was associated with any of the outcomes. t tests revealed that those with a complication were older (p < .05) and had higher pre-pregnancy BMI (p < .05), higher self-reported stress (p < .05), and lower IFN-γ (p < .05).

CONCLUSION

Findings suggest that longer and more variable sleep latency, as well as shorter sleep duration, is associated with shorter gestational age or a lower birth weight infant. Overall, the findings suggest that among a low-risk, healthy sample of pregnant women, sleep disturbance does not pose a substantial risk for adverse delivery outcomes.

Intraindividual variability in sleep and comorbid medical and mental health conditions

STUDY OBJECTIVES

Intraindividual variability (IIV) in sleep may be a risk factor for disease above the influence of mean sleep. Associations between IIV in sleep and risk for a comprehensive set of common medical and mental health conditions have not been assessed in a representative sample.

METHODS

This study examined mean and IIV in total sleep time (TST), sleep quality (SQ), sleep efficiency (SE), and circadian midpoint (CM) in 771 adults recruited for an epidemiological study. Participants completed 14 days of sleep diaries to assess TST, SQ, SE, and CM, after which they reported on medical conditions and mental health symptoms. Data were analyzed using logistic regression, and models controlled for gender, body mass index, age, and race.

RESULTS

Lower mean TST, SQ, and SE were related to increased odds of having gastrointestinal problems, depression, and anxiety. IIV in TST was related to increased odds of having neurological, breathing, and gastrointestinal problems, as well as pain and depression; all results held controlling for mean sleep and adjusting for false discovery rate. IIV in SQ and SE was not associated with odds of having any medical or mental health conditions after adjusting for false discovery rate, nor was IIV in CM or mean CM.

CONCLUSIONS

Confirming previous research, mean TST, SQ, and SE are related to risk for gastrointestinal problems, depression, and anxiety. IIV in TST may be a unique facet of disturbed sleep that is associated with increased risk for a diverse cluster of medical and mental health conditions.

Variability in Sleep Patterns: an Emerging Risk Factor for Hypertension

PURPOSE OF REVIEW

In this review, we summarize recent epidemiological data (2014-2019) that examine the association of sleep variability with blood pressure (BP), discuss potential underlying mechanisms, and highlight future research directions.

RECENT FINDINGS

Higher standard deviations of sleep duration and sleep-onset timing were not related to BP. However, a higher Sleep Regularity Index score was associated with lower odds of hypertension. Studies on social jetlag, a prevalent form of sleep variability, reported null associations. In contrast, lower interdaily stability in circadian rest-activity rhythms, a measure of invariability in sleep-wake cycles between days and synchronization to light and dark cycles, was associated with higher BP and greater hypertension odds, particularly among non-shift workers. Sleep variability is consistently associated with risk factors for hypertension. Evidence on sleep variability and BP is limited and varies depending on the measure used to characterize day-to-day variability in sleep. Studies that identify and utilize a standard definition of sleep variability, incorporate a 24-h ambulatory BP monitoring, and ensure coinciding timing of sleep and BP measurements are necessary to disentangle these relationships.

Do Physical Activity, Caloric Intake, and Sleep Vary Together Day to Day? Exploration of Intraindividual Variability in 3 Key Health Behaviors

BACKGROUND

Little is known about how daily fluctuations in health behaviors relate to chronic disease risk. The goal of this study was to examine whether variability in physical activity, caloric intake, and sleep is related to body composition (body mass index and body fat percentage).

METHODS

Healthy adults (N = 103; 64% female) were monitored for 7 days to assess physical activity (SenseWear Armband), caloric intake (daily food diaries), and sleep duration and timing (Actiwatch Spectrum). Data were analyzed using correlations (between- and within-subjects correlations) and regression.

RESULTS

The results demonstrated that variabilities in physical activity, caloric intake, and sleep were unrelated. Caloric intake and sleep variability were unrelated to body composition. At greater levels of physical activity variability, any level of physical activity was protective for body composition.

CONCLUSIONS

These results suggest that among healthy adults, variabilities in health behaviors may be independent of each other, and physical activity variability may be more strongly related to body composition among those who are less active.

Multidimensional Sleep and Mortality in Older Adults: A Machine-Learning Comparison With Other Risk Factors

BACKGROUND

Sleep characteristics related to duration, timing, continuity, and sleepiness are associated with mortality in older adults, but rarely considered in health recommendations. We applied machine learning to: (i) establish the predictive ability of a multidimensional self-reported sleep domain for all-cause and cardiovascular mortality in older adults relative to other established risk factors and (ii) to identify which sleep characteristics are most predictive.

METHODS

The analytic sample includes N = 8,668 older adults (54% female) aged 65-99 years with self-reported sleep characterization and longitudinal follow-up (≤15.5 years), aggregated from three epidemiological cohorts. We used variable importance (VIMP) metrics from a random survival forest to rank the predictive abilities of 47 measures and domains to which they belong. VIMPs > 0 indicate predictive variables/domains.

RESULTS

Multidimensional sleep was a significant predictor of all-cause (VIMP [99.9% confidence interval {CI}] = 0.94 [0.60, 1.29]) and cardiovascular (1.98 [1.31, 2.64]) mortality. For all-cause mortality, it ranked below that of the sociodemographic (3.94 [3.02, 4.87]), physical health (3.79 [3.01, 4.57]), and medication (1.33 [0.94, 1.73]) domains but above that of the health behaviors domain (0.22 [0.06, 0.38]). The domains were ranked similarly for cardiovascular mortality. The most predictive individual sleep characteristics across outcomes were time in bed, hours spent napping, and wake-up time.

CONCLUSION

Multidimensional sleep is an important predictor of mortality that should be considered among other more routinely used predictors. Future research should develop tools for measuring multidimensional sleep-especially those incorporating time in bed, napping, and timing-and test mechanistic pathways through which these characteristics relate to mortality.

A preliminary study of a composite sleep health score: associations with psychological distress, body mass index, and physical functioning in a low-income African American community

OBJECTIVES

Although multiple individual sleep measures (eg, sleep duration, satisfaction) have been linked to a wide range of physical and mental health conditions, scant research has examined how individual sleep dimensions may act independently or additively to influence health. The current study investigates associations of 5 sleep dimensions (duration, satisfaction, efficiency, timing, and regularity), analyzed separately and simultaneously, with psychological distress, body mass index, and physical functioning among a low-income, predominantly African American population.

DESIGN

We constructed a composite sleep health (SH) score from the sum of scores, representing "good' and "poor" ranges of 5 sleep measures (range 0-5).

SETTING

Two low-income, predominantly African American neighborhoods in Pittsburgh.

PARTICIPANTS

Participants included 738 community-dwelling adults (78% female and 98% black).

MEASUREMENTS

Actigraphy-based measures of sleep duration, regularity, timing, and efficiency, and self-reported sleep satisfaction. Outcomes included self-reported psychological distress, physical functioning, and measured body mass index (BMI).

RESULTS

Each 1-unit higher SH score was associated with 0.55-unit lower psychological distress score (range 0-24) and 2.23-unit higher physical functioning score. Participants with at least 2, 3, or 4 sleep dimensions in the "healthy" range, vs fewer, had lower psychological distress scores. Greater sleep satisfaction was associated with higher physical functioning, and longer sleep duration was associated with lower physical functioning. Neither the composite SH score nor any of the individual sleep dimensions were associated with BMI.

CONCLUSIONS

Assessing multiple sleep dimensions may provide a more comprehensive understanding of associations of sleep with psychological distress than assessing any single sleep dimension. Although no sleep measures were related to BMI in the current sample, analyses should be replicated in other samples to determine generalizability.

Insomnia and risk of mortality from all-cause, cardiovascular disease, and cancer: Systematic review and meta-analysis of prospective cohort studies

Growing evidence indicates that insomnia may be associated with mortality. However, these findings have been inconsistent. We systematically searched MEDLINE and EMBASE to identify prospective cohort studies that assessed the association between insomnia disorder/individual insomnia symptoms and the risk of mortality among adults aged ≥18 yrs. We addressed this association using summary hazard ratios (HRs) and 95% confidence intervals (CIs) calculated using random-effects meta-analysis, and the GRADE approach to rate the certainty of evidence. Twenty-nine cohorts including 1,598,628 individuals (55.3% men; mean age 63.7 yrs old) with a median follow-up duration of 10.5 yrs proved eligible. Difficulty falling asleep (DFA) and non-restorative sleep (NRS) were associated with an increased risk of all-cause mortality (DFA: HR = 1.13, 95%CI 1.03 to 1.23, p = 0.009, moderate certainty; NRS: HR = 1.23, 95%CI 1.07 to 1.42, p = 0.003, high certainty) and cardiovascular disease mortality (DFA: 1.20, 95%CI: 1.01, 1.43; p = 0.04, moderate certainty; NRS: HR = 1.48, 95%CI 1.06 to 2.06, p = 0.02, moderate certainty). Convincing associations between DFA and all-cause mortality were restricted to the mid to older-aged population (moderate credibility). Insomnia disorder, difficulty maintaining sleep, and early morning awakening proved to be unassociated with all-cause and cardiovascular disease mortality. No insomnia symptoms proved to be associated with cancer-related mortality.

Direct and indirect associations of cognitive reappraisal and suppression with disease biomarkers

OBJECTIVE

Habitual use of emotion regulation strategies may influence physical health. We examined whether the tendencies to employ cognitive reappraisal and suppression were associated with health biomarkers, and whether stress and sleep quality mediated these associations. Design & main outcome measures: Using data from the Biomarkers substudy (n = 1255) of the national Midlife in the U.S. Study, we tested the hypothesis that there would be indirect, but not direct, associations of cognitive reappraisal and suppression to biomarker indicators of multisystem physiological dysregulation, that is, allostatic load (AL). We computed the proportion of biomarkers in the highest risk quartile within seven biological systems, and summed these scores to compute AL. Associations with the biological systems were also examined separately.

RESULTS

Neither reappraisal nor suppression was directly associated with AL or biomarker function in the seven biological systems. Suppression was indirectly associated with higher AL and greater dysregulation in the inflammatory, metabolic, and hypothalamic-pituitary-adrenal systems via its relations to stress and sleep, p < 0.05. Reappraisal was indirectly associated with lower AL and less metabolic and inflammatory dysregulation, ps<0.05.

CONCLUSIONS

Suppression and reappraisal may have different downstream health effects via stress, sleep, and biomarker expression, suggesting malleable emotion regulation strategies may be an important intervention target.

The effect of moderate-intensity exercise on nightly variability in objectively measured sleep parameters among older women

Objective/Background: Exercise training has been demonstrated to beneficially influence mean-level measures of sleep; however, few studies have examined the impact of an exercise intervention on night-to-night variability in sleep. This study investigated whether four months of moderate-intensity exercise impacted night-to-night variability in sleep among older women. Methods: Participants (n = 49) were randomized to one of two moderate-intensity walking programs with different doses of energy expenditure: low-dose (n = 23: 8 kcal/kg of body weight per week) or high-dose (n = 26: 14 kcal/kg of body weight per week). Sleep parameters were assessed objectively via actigraphy at baseline, mid- (2 months), and postintervention (4 months). Nightly variability in each of the sleep parameters was calculated using the seven-day standard deviation (SD) and a coefficient of variation (SD/mean x 100%). Cardiorespiratory fitness (VO_2peak) was measured at baseline and postintervention using a graded treadmill test. Results: Both measures of nightly variability demonstrated a borderline to significantly lower amount of night-to-night variability in wake time after sleep onset (WASO) and number of awakenings at postintervention in comparison to baseline (p ≤ 0.05). Higher VO_2peak levels at baseline were associated with less time in bed and lower total sleep time variability throughout the exercise intervention (p < 0.05). Conclusion: Overall, participation in moderate-intensity exercise was observed to reduce the amount of nightly variability for WASO and number of awakenings over time in older women.

More evening preference is positively associated with systemic inflammation in prediabetes and type 2 diabetes patients

Currently it is not known whether morningness-eveningness preference in non-night shift working population is associated with systemic inflammation. This study investigated the relationship between morningness-eveningness and systemic inflammation, as measured by high-sensitivity C-reactive protein (hs-CRP) in 163 non-night shift working patients with abnormal glucose tolerance (86 type 2 diabetes and 77 prediabetes). Morningness-eveningness was assessed by Composite Scale of Morningness, and participants were screened for Obstructive sleep apnea (OSA). Sleep duration, efficiency, and variability were obtained using actigraphy, and depressive symptoms and dietary patterns were also captured. Participants' mean age was 54.7 ± 10.4 years and median hs-CRP was 1.39 (interquartile range 0.82, 3.33) mg/L. More evening preference was significantly associated with higher natural log transformed (ln) hs-CRP (B = -0.051, p = 0.001). Diabetes status, glycemic control, OSA severity, sleep duration, caloric consumption and timing were not related to hs-CRP. After adjusting for age, sex, body mass index, depressive symptoms, sleep efficiency, sleep variability, percentage of daily caloric intake from protein, and statin use, more evening preference was independently associated with higher ln hs-CRP (B = -0.032, p = 0.014). In summary, in non-night shift working patients with abnormal glucose tolerance, more evening preference was independently associated with higher systemic inflammation. This finding underscore the importance of circadian regulation on cardiovascular health.

Intraindividual sleep variability and its association with insomnia identity and poor sleep

OBJECTIVE

Insomnia identity refers to the conviction that one has insomnia, which can occur independently of poor sleep. Night-to-night variability in sleep (termed intraindividual variability [IIV]) may contribute to insomnia identity yet remain undetected via conventional mean analyses. This study compared sleep IIV across four subgroups: noncomplaining good sleepers (NG), complaining poor sleepers (CP), complaining good sleepers (CG), and noncomplaining poor sleepers (NP).

METHODS

This study analyzed 14 days of sleep diary data from 723 adults. Participants were classified according to presence/absence of a sleep complaint and presence/absence of poor sleep. A 2 × 2 multivariate analysis of covariance (MANCOVA) was performed to explore differences on five measures of sleep IIV: intraindividual standard deviation in total sleep time (iSD TST), sleep onset latency (iSD SOL), wake after sleep onset (iSD WASO), number of nightly awakenings (iSD NWAK), and sleep efficiency (iSD SE).

RESULTS

MANCOVA revealed significant main effects of poor sleep, sleep complaint, and their interaction on sleep IIV. Poor sleepers exhibited greater IIV across all sleep parameters compared to good sleepers. Similarly, individuals with a sleep complaint exhibited greater IIV compared to individuals with no complaint. The interaction revealed that iSD SOL was significantly greater among CP than NP, and iSD NWAK was significantly greater among CG than NG.

CONCLUSIONS

Greater night-to-night variability in specific sleep parameters was present among complaining versus noncomplaining sleepers in good and poor sleep subgroups. These findings suggest certain aspects of sleep consistency may be salient for treatment-seeking individuals based on their quantitative sleep status.

Effects of active and latent H. pylori infection coupled with chronic alcohol ingestion on cytokine profiles and markers of oxidative balance in men seropositive for H. pylori CagA Ab: An observational study

This study aimed to explore the effects of active and latent Helicobacter pylori infection coupled with alcohol consumption on cytokine profiles and markers of oxidative balance in men seropositive for H. pylori CagA Ab.The 100 male subjects were divided into groups with active H. pylori infection and H. pylori CagA Ab coupled with chronic alcohol ingestion (group A, n = 38), latent H. pylori infection with H. pylori CagA Ab coupled with chronic alcohol ingestion (group B, n = 30), and latent H. pylori infection with H. pylori CagA Ab without chronic alcohol ingestion (group C, n = 32).No differences in serum levels of CRP, IL-10, ADP, E-selectin, MDA, or SOD were detected between the 3 groups or between any 2 groups (all P > .05). The serum IL-6 and TNF-α concentrations in groups A and B were significantly lower than those in group C (P = .004, P = .005, P = .009, and P = .023). However, there were no differences in serum IL-6 and TNF-α between group A and group B (all P > .05).In conclusion, active or latent H. pylori infection coupled with chronic alcohol ingestion may decrease certain cytokines, that is, IL-6 and TNF-α, in men with H. pylori CagA Ab seropositivity. However, there was no difference in the detected cytokine profile between active and latent H. pylori infection coupled with chronic alcohol ingestion, and no changes were detected in markers of oxidative balance in men with H. pylori CagA Ab.

Sleep Schedule Regularity Is Associated with Sleep Duration in Older Australian Adults: Implications for Improving the Sleep Health and Wellbeing of Our Aging Population

OBJECTIVES

The National Sleep Foundation (NSF) recommends 7 to 9 hours of sleep per night for adults ≥ 65 years of age. Sleep duration below 7h per night has been associated with negative health consequences, so enabling older adults to obtain at least 7 hours per night is important for health and wellbeing. However, little is known about behavioral factors that support sleep duration (≥ 7h/24h) in this group. Our aim was to determine factors associated with sleep duration in older adults, and evaluate the utility of sleep schedule regularity in particular, given the relationship between lifestyle regularity (of which sleep is an important component) and health in this population.

METHODS

A sample of 311 Australian adults (≥ 65 years old; 156 male, 155 female) completed a telephone survey assessing sleep history over the prior 24 hours, sleep schedule regularity, demographic and health factors as part of a larger study of the Australian population.

RESULTS

Sleep schedules with variability in bed and rise times of > 60 minutes were associated with increased odds of reporting sleep duration below 7 hours per night (< 7h/24h; OR = 2.38, CI = 1.26-4.48, p = .007). No other behaviors were associated with meeting sleep duration recommendations.

CONCLUSIONS

Sleep schedule regularity may be associated with sleep duration (≥ 7h/24h) in older adults.

CLINICAL IMPLICATIONS

Empowering older adults to maintain sleep schedule regularity may be a practical and efficacious strategy to support sleep durations that are in line with recommendations (≥ 7h/24h).

Commuting and Sleep: Results From the Hispanic Community Health Study/Study of Latinos Sueño Ancillary Study

INTRODUCTION

Commute time is associated with reduced sleep time, but previous studies have relied on self-reported sleep assessment. The present study investigated the relationships between commute time for employment and objective sleep patterns among non-shift working U.S. Hispanic/Latino adults.

METHODS

From 2010 to 2013, Hispanic/Latino employed, non-shift-working adults (n=760, aged 18-64 years) from the Sueño study, ancillary to the Hispanic Community Health Study/Study of Latinos, reported their total daily commute time to and from work, completed questionnaires on sleep and other health behaviors, and wore wrist actigraphs to record sleep duration, continuity, and variability for 1 week. Survey linear regression models of the actigraphic and self-reported sleep measures regressed on categorized commute time (short: 1-44 minutes; moderate: 45-89 minutes; long: ≥90 minutes) were built adjusting for relevant covariates. For associations that suggested a linear relationship, continuous commute time was modeled as the exposure. Moderation effects by age, sex, income, and depressive symptoms also were explored.

RESULTS

Commute time was linearly related to sleep duration on work days such that each additional hour of commute time conferred 15 minutes of sleep loss (p=0.01). Compared with short commutes, individuals with moderate commutes had greater sleep duration variability (p=0.04) and lower interdaily stability (p=0.046, a measure of sleep/wake schedule regularity). No significant associations were detected for self-reported sleep measures.

CONCLUSIONS

Commute time is significantly associated with actigraphy-measured sleep duration and regularity among Hispanic/Latino adults. Interventions to shorten commute times should be evaluated to help improve sleep habits in this minority population.

Impact of caregiving for older people and pro-inflammatory biomarkers among caregivers: a systematic review

INTRODUCTION

Evidence suggests that providing care for an older loved one may present a risk to the health of the caregiver. To understand the link between the psychosocial stress of caregiving and damage to the health of caregivers, numerous studies have assessed the presence of inflammatory biomarkers among caregivers. These biomarkers are measured to understand the relationships between the social stress of caregiving and the health of caregivers.

OBJECTIVE

To provide a complete summary of the current literature regarding the most clinically relevant pro-inflammatory biomarkers associated with caregiving.

METHODS

We searched articles in MEDLINE and EMBASE from January 1980 to 30 April 2016 for all studies that assessed biomarkers (cortisol, interleukin-6 and c-reactive protein) among caregivers of community-dwelling older persons. The quality of the selected studies was assessed by two reviewers using the STROBE or CONSORT checklist.

RESULTS

Twenty-four studies were included. Most of the studies were cross-sectional and focused on dementia caregiving. Increases in biomarkers were associated with problems such as disturbed sleep, burden or pain and caregiving characteristics, including daily stressors and the duration of caregiving. Cognitive-behavioural therapy and participation in leisure activities were associated with significantly lower levels of cortisol and IL-6, respectively.

DISCUSSION

We found little evidence concerning the association between caregiving status and biomarkers of stress and inflammation. We discuss potential sources of bias and suggest some directions for further research. This stress model can be expanded by taking into account the positive aspects of caregiving and the potential resources of caregivers.