A novel approach using actigraphy to quantify the level of disruption of sleep by in-home polysomnography: the MrOS Sleep Study: Sleep disruption by polysomnography

Validation of a Textile-Based Wearable Measuring Electrocardiogram and Breathing Frequency for Sleep Apnea Monitoring

Sleep apnea (SA) is a prevalent disorder characterized by recurrent events of nocturnal apnea. Polysomnography (PSG) represents the gold standard for SA diagnosis. This laboratory-based procedure is complex and costly, and less cumbersome wearable devices have been proposed for SA detection and monitoring. A novel textile multi-sensor monitoring belt recording electrocardiogram (ECG) and breathing frequency (BF) measured by thorax excursion was developed and tested in a sleep laboratory for validation purposes. The aim of the current study was to evaluate the diagnostic performance of ECG-derived heart rate variability and BF-derived breathing rate variability and their combination for the detection of sleep apnea in a population of patients with a suspicion of SA. Fifty-one patients with a suspicion of SA were recruited in the sleep laboratory of the Cantonal Hospital St. Gallen. Patients were equipped with the monitoring belt and underwent a single overnight laboratory-based PSG. In addition, some patients further tested the monitoring belt at home. The ECG and BF signals from the belt were compared to PSG signals using the Bland-Altman methodology. Heart rate and breathing rate variability analyses were performed. Features derived from these analyses were used to build a support vector machine (SVM) classifier for the prediction of SA severity. Model performance was assessed using receiver operating characteristics (ROC) curves. Patients included 35 males and 16 females with a median age of 49 years (range: 21 to 65) and a median apnea-hypopnea index (AHI) of 33 (IQR: 16 to 58). Belt-derived data provided ECG and BF signals with a low bias and in good agreement with PSG-derived signals. The combined ECG and BF signals improved the classification accuracy for SA (area under the ROC curve: 0.98; sensitivity and specificity greater than 90%) compared to single parameter classification based on either ECG or BF alone. This novel wearable device combining ECG and BF provided accurate signals in good agreement with the gold standard PSG. Due to its unobtrusive nature, it is potentially interesting for multi-night assessments and home-based patient follow-up.

Self-reported sleepiness associates with greater brain and cortical volume and lower prevalence of ischemic covert brain infarcts in a community sample

STUDY OBJECTIVES

We evaluated if self-reported sleepiness was associated with neuroimaging markers of brain aging and ischemic damage in a large community-based sample.

METHODS

Participants from the Framingham Heart Study Offspring cohort (n = 468, 62.5 ± 8.7 years old, 49.6%M) free of dementia, stroke, and neurological diseases, completed sleep questionnaires and polysomnography followed by magnetic resonance imaging (MRI), 3 years later on average. We used linear and logistic regression models to evaluate the associations between Epworth Sleepiness Scale (ESS) scores and total brain, cortical and subcortical gray matter, and white matter hyperintensities volumes, and the presence of covert brain infarcts.

RESULTS

Higher sleepiness scores were associated with larger total brain volume, greater cortical gray matter volume, and a lower prevalence of covert brain infarcts, even when adjusting for a large array of potential confounders, including demographics, sleep profiles and disorders, organic health diseases, and proxies for daytime cognitive and physical activities. Interactions indicated that more sleepiness was associated with larger cortical gray matter volume in men only and in APOE ε4 noncarriers, whereas a trend for smaller cortical gray matter volume was observed in carriers. In longitudinal analyses, those with stable excessive daytime sleepiness over time had greater total brain and cortical gray matter volumes, whereas baseline sleepiness scores were not associated with subsequent atrophy or cognitive decline.

CONCLUSION

Our findings suggest that sleepiness is not necessarily a marker of poor brain health when not explained by diseases or sleep debt and sleep disorders. Rather, sleepiness could be a marker of preserved sleep-regulatory processes and brain health in some cases.

Neural mechanism of the relationship between sleep efficiency and clinical improvement in major depressive disorder: A longitudinal functional magnetic resonance imaging study

BACKGROUND

Antidepressants represent the most common treatment of choice for major depressive disorder (MDD). In this study, we aimed to explore the status-related changes (acute vs. remitted status) in brain function in patients with MDD.

METHODS

Regular antidepressant medications (an average of 7 months after the initial visit, remitted status) were received by 48 patients with MDD. All the patients underwent MRI and polysomnography examinations as well as clinical assessment at each visit.

RESULTS

We found that baseline fractional amplitude of low-frequency fluctuations (fALFF) of right superior parietal gyrus (SPG) and middle frontal gyrus could predict depression and anxiety symptoms improvement from acute to remitted status in patients with MDD, respectively. Moreover, we found a significant positive correlation between the fALFF of right SPG and baseline sleep efficiency (SE) in patients with MDD. Further mediation analysis revealed that the fALFF of right SPG mediated the relationship between baseline SE and depressive symptom improvement.

CONCLUSION

Apart from highlighting the fALFF as a potential prognostic indicator to predict and track disease progression in patients with MDD, these findings might provide a neural mechanism basis for improving sleep quality of patients with MDD and thus promoting the recovery of clinical symptoms, as well as provide a practical basis for clinical interventions in patients with MDD with sleep disorders.

Requirements and Architecture of a Cloud Based Insomnia Therapy and Diagnosis Platform: A Smart Cities Approach

Insomnia is the most common sleep disorder worldwide. Its effects generate economic costs in the millions but could be effectively reduced using digitally provisioned cognitive behavioural therapy. However, traditional acquisition and maintenance of the necessary technical infrastructure requires high financial and personnel expenses. Sleep analysis is still mostly done in artificial settings in clinical environments. Nevertheless, innovative IT infrastructure, such as mHealth and cloud service solutions for home monitoring, are available and allow context-aware service provision following the Smart Cities paradigm. This paper aims to conceptualise a digital, cloud-based platform with context-aware data storage that supports diagnosis and therapy of non-organic insomnia. In a first step, requirements needed for a remote diagnosis, therapy, and monitoring system are identified. Then, the software architecture is drafted based on the above mentioned requirements. Lastly, an implementation concept of the software architecture is proposed through selecting and combining eleven cloud computing services. This paper shows how treatment and diagnosis of a common medical issue could be supported effectively and cost-efficiently by utilising state-of-the-art technology. The paper demonstrates the relevance of context-aware data collection and disease understanding as well as the requirements regarding health service provision in a Smart Cities context. In contrast to existing systems, we provide a cloud-based and requirement-driven reference architecture. The applied methodology can be used for the development, design, and evaluation of other remote and context-aware diagnosis and therapy systems. Considerations of additional aspects regarding cost, methods for data analytics as well as general data security and safety are discussed.

Association of Depressive Symptoms with Sleep Disturbance: A Co-twin Control Study

BACKGROUND

Few studies have comprehensively evaluated the association of depression with sleep disturbance using a controlled twin study design.

PURPOSE

To cross-sectionally evaluate the association of depression with both objective and subjective sleep disturbance.

METHODS

We studied 246 members of the Vietnam Era Twin Registry. We measured depressive symptoms using the Beck Depression Inventory-II (BDI) and assessed major depression using structured clinical interviews. Twins underwent one-night polysomnography and 7-day actigraphy to derive measures of objective sleep and completed the Pittsburgh Sleep Quality Index for subjective sleep. Multivariable mixed-effects models were used to examine the association.

RESULTS

Twins were all male, mostly white (97%), with a mean (SD) age of 68 (2). The mean (SD) BDI was 5.9 (6.3), and 49 (20%) met the criteria for major depression. For polysomnography, each 5-unit higher BDI, within-pair, was significantly associated with 19.7 min longer rapid eye movement (REM) sleep latency, and 1.1% shorter REM sleep after multivariable adjustment. BDI was not associated with sleep architecture or sleep-disordered breathing. For actigraphy, a higher BDI, within-pair, was significantly associated with lower sleep efficiency, more fragmentation and higher variability in sleep duration. BDI was associated with almost all dimensions of self-reported sleep disturbance. Results did not differ by zygosity, and remained consistent using major depression instead of BDI and were independent of the presence of comorbid posttraumatic stress disorder and antidepressant use.

CONCLUSIONS

Depression is associated with REM sleep disruption in lab and sleep fragmentation and sleep variability at home, but not with sleep architecture or sleep-disordered breathing.

The relationship between sleep efficiency and clinical symptoms is mediated by brain function in major depressive disorder

BACKGROUND

Sleep disturbance is a common and key symptom that affects most of patients with major depressive disorder (MDD). However, neural substrates underlying sleep disturbance and their clinical relevance in depression remain unclear.

METHODS

Ninety-six MDD patients underwent resting-state functional MRI. Fractional amplitude of low-frequency fluctuation (fALFF) and resting-state functional connectivity (rsFC) were used to measure brain function. Overnight polysomnography was performed to objectively measure sleep efficiency (SE), which was used to classify patients into normal sleep efficiency (NSE) and low sleep efficiency (LSE) groups. Between-group differences in fALFF and rsFC were examined using two-sample t-tests. Moreover, correlation and mediation analyses were conducted to test for potential associations between SE, brain functional changes, and clinical variables.

RESULTS

LSE group showed decreased fALFF in right cuneus, thalamus, and middle temporal gyrus compared to NSE group. MDD patients with low SE also exhibited lower rsFC of right cuneus to right lateral temporal cortex, which was associated with more severe depression and anxiety symptoms. More importantly, mediation analyses revealed that the relationships between SE and severity of depression and anxiety symptoms were significantly mediated by the altered rsFC. In addition, these low SE-related brain functional alterations were not affected by antidepressant medication and were independent of structural changes.

LIMITATIONS

The lack of healthy controls because of "first-night effect".

CONCLUSION

These findings not only may expand existing knowledge about neuropathology of sleep disturbance in depression, but also may inform real-world clinical practice by improving depression and anxiety symptoms through sleep regulation.

Classification of Sleep Apnea Severity by Electrocardiogram Monitoring Using a Novel Wearable Device

Sleep apnea (SA) is a prevalent disorder diagnosed by polysomnography (PSG) based on the number of apnea–hypopnea events per hour of sleep (apnea–hypopnea index, AHI). PSG is expensive and technically complex; therefore, its use is rather limited to the initial diagnostic phase and simpler devices are required for long-term follow-up. The validity of single-parameter wearable devices for the assessment of sleep apnea severity is still debated. In this context, a wearable electrocardiogram (ECG) acquisition system (ECG belt) was developed and its suitability for the classification of sleep apnea severity was investigated using heart rate variability analysis with or without data pre-filtering. Several classification algorithms were compared and support vector machine was preferred due to its simplicity and overall performance. Whole-night ECG signals from 241 patients with a suspicion of sleep apnea were recorded using both the ECG belt and patched ECG during PSG recordings. 65% of patients had an obstructive sleep apnea and the median AHI was 21 [IQR: 7–40] h−1. The classification accuracy obtained from the ECG belt (accuracy: 72%, sensitivity: 70%, specificity: 74%) was comparable to the patched ECG (accuracy: 74%, sensitivity: 88%, specificity: 61%). The highest classification accuracy was obtained for the discrimination between individuals with no or mild SA vs. moderate to severe SA. In conclusion, the ECG belt provided signals comparable to patched ECG and could be used for the assessment of sleep apnea severity, especially during follow-up.

Sleep and stress before and after duty across residency years under 2017 ACGME hours

INTRODUCTION

Residents may differentially experience high stress and poor sleep across multiple post-graduate years (PGYs), negatively affecting safety. This study characterized sleep and stress among medical and surgical residents across multiple PGYs and at specific times surrounding duty.

METHOD

Thirty-two medical and surgical residents (M_age = 28.6 years; 56% male) across PGYs 1-5 participated in 3 appointments (immediately before duty, after duty, and on an off day) providing 96 data points. Sleep, stress, and occupational fatigue were measured by both self-report and objectively (actigraphy, salivary coritsol).

RESULTS

Residents averaged 7 h of actigraphy-estimated sleep per night but varied ±3 h day-to-day. Residents reported clinically poor sleep quality. Life stress decreased by PGY-2. All residents averaged elevated life stress values. Poor sleep quality did not differ among PGY cohorts.

DISCUSSION

Poor sleep quality is similar between early residency cohorts (PGY-1) and later residency cohorts (PGY-3+). Persistent fatigue is highest in later residency cohorts. Even the most experienced residents may struggle with persisting fatigue. Current hour policies may have shortcomings in addressing this risk.

Contactless recording of sleep apnea and periodic leg movements by nocturnal 3-D-video and subsequent visual perceptive computing

Contactless measurements during the night by a 3-D-camera are less time-consuming in comparison to polysomnography because they do not require sophisticated wiring. However, it is not clear what might be the diagnostic benefit and accuracy of this technology. We investigated 59 persons simultaneously by polysomnography and 3-D-camera and visual perceptive computing (19 patients with restless legs syndrome (RLS), 21 patients with obstructive sleep apnea (OSA), and 19 healthy volunteers). There was a significant correlation between the apnea hypopnea index (AHI) measured by polysomnography and respiratory events measured with the 3-D-camera in OSA patients (r = 0.823; p < 0.001). The receiver operating characteristic curve yielded a sensitivity of 90% for OSA with a specificity of 71.4%. In RLS patients 72.8% of leg movements confirmed by polysomnography could be detected by 3-D-video and a significant moderate correlation was found between PLM measured by polysomnography and by the 3-D-camera (RLS: r = 0.654; p = 0.004). In total, 95.4% of the sleep epochs were correctly classified by the machine learning approach, but only 32.5% of awake epochs. Further studies should investigate, if this technique might be an alternative to home sleep testing in persons with an increased pre-test probability for OSA.

Relation between ambulatory actigraphy and laboratory polysomnography in insomnia practice and research

Actigraphy is increasingly used in practice and research studies because of its relative low cost and decreased subject burden. How multiple nights of at-home actigraphy compare to one independent night of in-laboratory polysomnography (PSG) has not been examined in people with insomnia. Using event markers (MARK) to set time in bed (TIB) compared to automatic program analysis (AUTO) has not been systematically evaluated. Subjects (n = 30) meeting DSM-5 criteria for insomnia and in-laboratory PSG sleep efficiency (SE) of <85% were studied. Subjects were free of psychiatric, sleep or circadian disorders, other chronic conditions and medications that effect sleep. Subjects had an in-laboratory PSG, then were sent home for 7 nights with Philips Actiwatch Spectrum Plus. Data were analysed using Philips Actiware version 6. Using the mean of seven nights, TIB, total sleep time (TST), SE, sleep-onset latency (SOL) and wake after sleep onset (WASO) were examined. Compared to PSG, AUTO showed longer TIB and TST and less WASO. MARK only differed from PSG with decreased WASO. Differences between the PSG night and the following night at home were found, with better sleep on the first night home. Actigraphy in people with insomnia over seven nights is a valid indicator of sleep compared to an independent in-laboratory PSG. Event markers increased the validity of actigraphy, showing no difference in TIB, TST, SE and SOL. AUTO was representative of SE and SOL. Increased SE and TST without increased TIB suggests possible compensatory sleep the first at night home after in-laboratory PSG.

Single-use suvorexant for treating insomnia during overnight polysomnography in patients with suspected obstructive sleep apnea: a single-center experience

Purpose

Although patients with suspected obstructive sleep apnea (OSA) might suffer difficulty in falling asleep during overnight polysomnography (PSG), standard hypnotics to obtain sleep during PSG have not been established. The aim of this study was to investigate the safety and efficacy of a new hypnotic agent, suvorexant, a dual orexin receptor antagonist, for insomnia in suspected OSA patients during in-laboratory PSG.

Patients and methods

An observational study was conducted during PSG for 149 patients with suspected OSA who had no insomnia at home. Patients with difficulty in falling asleep during PSG were optionally permitted to take single-use suvorexant. Patients with residual severe insomnia (>1 hour) after taking suvorexant were permitted to take an add-on use zolpidem. Clinical data and sleep questionnaire results were analyzed between a no insomnia group (without hypnotics) and an insomnia group (treated with suvorexant).

Results

Among 84 patients who experienced insomnia during PSG and required hypnotics (the insomnia group; treated with suvorexant), 44 (52.4%) achieved sufficient subjective sleep with single-use of suvorexant, while the other 40 (47.6%) required suvorexant plus zolpidem. An apnea hypopnea index (AHI) of ≥5 was observed in 144 out of 149 patients with predominantly obstructive respiratory events. Among those patients, 70.8% in the no insomnia group and 63.1% in the insomnia group had severe OSA. Regarding both subjective sleep time and morning mood, significant differences between the no insomnia group and the insomnia group were not observed. No patient taking suvorexant had an adverse event, such as delirium or falling.

Conclusion

Single-use suvorexant seems to be a safe and effective (but mild) hypnotic agent for suspected OSA patients with insomnia during in-laboratory PSG.

The Relationship Between PSG and Morning/Evening Emotional Parameters in Patients With Insomnia Disorder and Good Sleepers

Objectives and Introduction: It is as yet unclear how polysomnographically determined sleep parameters determine emotional well-being both generally and particularly in patients with Insomnia Disorder (ID). ID is a frequent and disabling health condition associated with both day- and nighttime hyperarousal, linked to negative sleep-related ruminations as a cognitive component. Information on the immediate influence of objective sleep quality on emotional parameters is important for therapeutic approaches. Methods: The relationship between objective sleep parameters and two emotional questionnaire items obtained both for evening and morning, relaxation and emotional balance, was determined for both sleep lab nights in 161 ID patients and 161 age and gender matched good sleepers (retrospective sample from the Freiburg data base, 98 female, 63 male in each group, age ID: 42.16 ± 11.55, GSC: 41.91 ± 11.30 years). Multivariate mixed effects analysis, corrected for global influences of group, age and first/second night, was employed to determine between- and within-subject influences of sleep and emotional parameters. Results: Main effects: Within-subject, relaxation in the evening was strongly associated with sleep efficiency, REM latency and low arousal index in NREM sleep. No such influence was significant for emotional balance. Also between subjects, evening relaxation was related to increased sleep efficiency. Group interactions: Patients with larger relaxation values in the evening showed a larger reduction of the number of wake periods and the awakening index in NREM sleep than GSC subjects. Discussion: Unexpectedly, no general influence of emotional balance on sleep was found. The subjective feeling of relaxation, however, was associated with sleep efficiency, REM latency and low NREM sleep arousal index. While the first association may be obvious, a direct link to REM latency and NREM arousal index has not previously been shown. We could also directly observe that the number of wake periods in the PSG is more strongly influenced by evening relaxation in ID patients than in good sleepers, asserting the importance of sleep perception and attitude toward sleep in the therapeutic process.

Practical aspects of actigraphy and approaches in clinical and research domains

Actigraphy involves acquisition of data using a movement sensor worn continuously on the nondominant wrist, typically for a week or more. Computer-based algorithms estimate sleep episodes by analysis of continuous minutes of no to low movement, or spans of time when movement is relatively low compared with movements during presumed ambulatory wakefulness. Inherent advantages of actigraphy over polysomnography include its noninvasive nature, cost-effectiveness, lesser burden on patients/research participants, and ability to collect data over multiple days/nights, thereby allowing examination of sleep-wake patterning. Therefore, actigraphy is emerging as a common method to objectively assess sleep parameters providing estimates of sleep duration and continuity. Modes of actigraphy data collection, scoring algorithms, sleep quality/disturbance measures, validation studies, and clinical and research applications are discussed.

Sleep apnea and femoral neck BMD among Singaporean mid-life women

The relationship between sleep apnea and bone health remains controversial. This study explored the relationship between sleep apnea and femoral neck BMD in midlife Asian women. Partner-witnessed apnea predicted higher femoral neck BMD, an effect validated by the STOP index. Our findings suggest that sleep apnea may protect bone health.

PURPOSE

The menopause transition is associated with decline in bone mineral density (BMD) and sleep quality. However, any relationship between these two factors remains controversial. This study explored the association between sleep apnea and femoral neck BMD in middle-aged women.

METHODS

Participants (n = 1201) aged 45-69 years attending well-women visits at the National University Hospital, Singapore were recruited. Self-reported breathing discomfort and snoring, partner-witnessed apnea and snoring were assessed from the Pittsburgh Sleep Quality Index. Femoral neck BMD was assessed with dual-energy X-ray absorptiometry scan and classified into tertiles based on T-scores. Factors reported to affect sleep apnea and bone health in medical literature were potential covariates, p < 0.10. Multivariable ordinal regression analyses assessed associations between sleep measures and BMD. To further validate our findings, we analyzed four sleep apnea characteristics from the STOP questionnaire, a screening tool for sleep apnea. All analyses were performed using SPSS version 20.0.

RESULTS

Mean (SD) age of participants was 56.3 (6.2) years. Partner-witnessed apnea predicted higher BMD tertiles (OR per unit increase in severity 1.39, 95% CI [1.02, 1.89]), independent of age, ethnicity, diabetes, BMI, and handgrip strength. This was further corroborated by the STOP index (OR 1.45, 95% CI [1.07, 1.96]).

CONCLUSIONS

This study adds to the literature on sleep apnea and bone health in a non-Caucasian and younger population. Our findings support OSA-associated intermittent hypoxia protecting bone health.

The use of accelerometry as a tool to measure disturbed nocturnal sleep in Parkinson's disease

Sleep disturbances are common in Parkinson’s disease (PD). We used the Parkinson’s KinetiGraph (PKG), an objective movement recording system for PD to assess night time sleep in 155 people aged over 60 and without PD (controls), 72 people with PD (PwP) and 46 subjects undergoing a Polysomnogram (PSG: 36 with sleep disorder and 10 with normal sleep). The PKG system uses a wrist worn logger to capture acceleration and derive a bradykinesia score (BKS) every 2 min over 6 days. The BKS ranges from 0–160 with higher scores associated with lesser mobility. Previously we showed that BKS > 80 were associated with day time sleep and used this to produce scores for night time sleep: Efficiency (Percent time with BKS > 80), Fragmentation (Average duration of runs of BKS > 80) and Sleep Quality (BKS > 111 as a representation of atonia). There was a fair association with BKS score and sleep level as judged by PSG. Using these PKG scores, it was possible to distinguish between normal and abnormal PSG studies with good Selectivity (86%) and Sensitivity (80%). The PKG’s sleep scores were significantly different in PD and Controls and correlated with a subject’s self-assessment (PDSS 2) of the quality, wakefulness and restlessness. Using both the PDSS 2 and the PKG, it was apparent that sleep disturbances were apparent early in disease in many PD subjects and that subjects with poor night time sleep were more likely to have day time sleepiness. This system shows promise as a quantitative score for assessing sleep in Parkinson’s disease.

A movement recording system reveals the occurrence of sleep disturbances in the early stages of Parkinson’s disease (PD). Malcolm Horne, a movement disorders expert at the University in Melbourne, and colleagues assessed night time sleep in 72 patients with PD using a wrist-worn device that captures movement patterns. The Parkinson’s KinetiGraph (PKG) system derives scores that are associated with sleep stages and correlate with patients’ self-assessment of sleep quality, wakefulness and restlessness. Significant differences between the PKG sleep scores of PD patients and age-matched healthy controls confirmed that night time sleep disturbances and day time sleepiness worsen as the disease progresses. Abnormal PKG scores were found in patients affected by the disease for only 3 years highlighting the extent to which sleep is disrupted in early-stage PD.

The first night effect in multiple sclerosis patients undergoing home-based polysomnography

BACKGROUND

The first night effect (FNE) is a polysomnography (PSG) habituation effect in the first of several consecutive in-laboratory PSGs (I-PSGs). The FNE is caused by the discomfort provoked by electrodes and cables and the exposure to an unfamiliar environment. A reverse FNE (RFNE) with an improved sleep in the first night is characteristic of insomnia, presumably because the video PSG in the sleep laboratory leads to a decrease in the negatively toned cognitive activity. Therefore, two or more I-PSGs are required for an accurate diagnosis. Although the FNE is well documented in I-PSG, little is known about the FNE and the RFNE in home-based PSGs (H-PSGs).

METHODS

This is a retrospective analysis of a recently published cross-sectional study using H-PSG. Sixty-three consecutive patients suffering from multiple sclerosis (MS) were investigated by two consecutive H-PSGs without video. The differences between the first and second H-PSGs were analyzed. The patients were classified into four subgroups: no sleep disorder, insomnia, sleep-related breathing disorders (SRBDs), and periodic limb movement disorder or restless legs syndrome (PLMD/RLS).

RESULTS

MS patients suffering from insomnia showed no RFNE. MS patients with SRBD or PLMD/RLS showed no reduced sleep efficiency but significantly less slow wave sleep. Furthermore, SRBD patients showed significantly less non-rapid eye movement (NREM) sleep, and PLMD/RLS patients were significantly awake longer in the first night after sleep onset (increased wake-after-sleep-onset time) and showed a higher rapid eye movement (REM) latency.

CONCLUSION

SRBD and PLMD/RLS patients showed a significant FNE. Two consecutive H-PSGs are required in these patients to obtain a precise hypnogram even in the ambulatory field. In MS patients suffering from insomnia, no RFNE was found, and in insomnia patients one H-PSG seems to be sufficient.

Rest-activity circadian rhythms and bone mineral density in elderly men

Background

Disrupted rest-activity circadian rhythm (RAR) patterns have been associated with poor health outcomes (i.e. diminished cognitive function, increased risk of dementia and falls). Circadian time cues in bone influence the differentiation of osteoblasts and osteoclasts, and bone turnover markers exhibit circadian variation; relationships between bone outcomes and RAR are emerging areas of research. We evaluated associations between RAR and areal bone mineral density (aBMD) at the total hip and femoral neck in older men from the Osteoporotic Fractures in Men (MrOS) cohort. We hypothesized that weaker RAR patterns would be associated with lower aBMD.

Methods

MrOS is an ongoing prospective cohort study following ambulatory men ≥ 65 years (n = 5994) at 6 U.S. clinics (baseline enrollment 3/2000–4/2002); participants for this analysis are from an ancillary study, Outcomes of Sleep Disorders in Older Men (MrOS Sleep). We included data from men who had technically adequate measures of RAR and aBMD at Sleep Visit 1 (12/2003–3/2005), with repeat aBMD at core Visit 3 (3/2007–3/2009) (n = 2412; mean age at Sleep Visit 1: 75.7 ± 5.2 years). aBMD was measured by dual energy x-ray absorptiometry (DXA). Actigraphs worn on the non-dominant wrist were used to collect circadian activity data over 4.8 ± 0.8 consecutive 24-hour periods. An extension of the traditional cosine curve was used to fit RAR to the activity data [Ancoli-Israel et al., 2003; Marler et al., 2006]. Six RAR parameters were evaluated: acrophase (time of peak activity), amplitude (rhythm strength), mesor (mean of activity fitted curve), pseudo F-statistic (overall circadian rhythmicity of rest and activity), alpha statistic (daytime to nighttime activity ratio), and beta statistic (daytime activity). Associations between RAR and aBMD (Sleep Visit 1), and RAR and ΔaBMD (Sleep Visit 1-Visit 3) were assessed with generalized linear models. Covariates included age, clinic site, physical activity, race, comorbidity, body mass index (BMI), smoking, alcohol, caffeine, beta blocker use, serum 25(OH) vitamin D and urinary melatonin and calcium.

Results

Pseudo F-statistic was significantly associated with total hip aBMD (p-trend = 0.009), femoral neck aBMD (p-trend = 0.007) and total hip ΔaBMD (p-trend = 0.017) in minimally adjusted models but not after multivariate (MV) adjustment. Alpha statistic was significantly associated with femoral neck aBMD (p-trend = 0.029) and femoral neck ΔaBMD (p-trend = 0.019) in minimally adjusted models; significance was retained in the femoral neck ΔaBMD model (p-trend = 0.034) after MV adjustment. There were no consistent, significant associations between the other RAR variables and aBMD or ΔaBMD.

Conclusions

The data demonstrate modest associations between overall circadian rhythmicity of rest and activity (measured by pseudo F-statistic), as well as daytime to nighttime activity ratio (measured by alpha statistic), aBMD and ΔaBMD, but adjustment for covariates related to lifestyle, BMI and comorbidities attenuated most of these associations. These results suggest that RAR patterns are not independently associated with aBMD or four-year ΔaBMD at the total hip or femoral neck in older men, but additional research is needed.

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Disrupted rest-activity circadian rhythm (RAR) undermines health outcomes.

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We modeled RAR patterns and areal bone mineral density (aBMD) in older men.

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Most associations lost significance after multivariate adjustment.

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RAR patterns are not independently associated with aBMD or ΔaBMD in older men.