Mood Influences the Concordance of Subjective and Objective Measures of Sleep Duration in Older Adults

Objective/Background: Sleep plays a central role in maintaining health and cognition. In most epidemiologic studies, sleep is evaluated by self-report questionnaires but several reports suggest that these evaluations might be less accurate than objective measures such as polysomnography or actigraphy. Determinants of the discrepancy between objective and subjective measures remain to be investigated. The aim of this pilot-study was to examine the role of mood states in determining the discrepancy observed between objective and subjective measures of sleep duration in older adults.Patients/Methods: Objective sleep quantity and quality were recorded by actigraphy in a sample of 45 elderly subjects over at least three consecutive nights. Subjective sleep duration and supplementary data, such as mood status and memory, were evaluated using Ecological Momentary Assessment (EMA).Results: A significant discrepancy was observed between EMA and actigraphic measures of sleep duration (p<0.001). The magnitude of this difference was explained by the patient’s mood status (p=0.020). No association was found between the magnitude of this discrepancy and age, sex, sleep quality or memory performance.Conclusion: The discrepancy classically observed between objective and subjective measures of sleep duration can be explained by mood status at the time of awakening. These results have potential implications for epidemiologic and clinical studies examining sleep as a risk factor for morbidity or mortality

Activity/rest cycle and disturbances of structural backbone of cerebral networks in aging.

OBJECTIVE: Although aging is associated with alterations of both activity/rest cycle and brain structure, few studies have evaluated associations between these processes. The aim of this study was to examine relationship between activity/rest cycle quality and brain structural integrity in aging subjects by exploring both grey and white matter compartments. MATERIAL AND METHODS: Fifty-eight elderly subjects (76±0.5 years; 41% female) without dementia, sleep disorders and medications were included in the analysis. Actigraphy was used to measure parameters of activity/rest cycle (24-h amplitude, 24-h fragmentation and 24-h stability) and sleep (total sleep time and sleep fragmentation) over a minimal period of 5 days. Whole brain linear regression analyses were performed on grey matter volumes maps using voxel based morphometry and on white matter integrity using tract based statistics analyses. RESULTS: A lower 24-h amplitude and a higher sleep fragmentation were independently associated with a reduction of white matter integrity in models including age and gender as covariates. The association between 24-h amplitude and white matter integrity decreased but remained significant in a model accounted for sleep fragmentation, indicating a specific effect of 24-h cycle disturbances. No association with grey matter volumes was observed. CONCLUSION: In elderly, not only sleep but also 24-h cycle disturbances were associated with altered structural connectivity. This alteration of structural backbone networks related to activity/rest cycle disturbances in aging might constitute a cerebral frailty factor for the development of cognitive impairment

pyActigraphy: Open-source python package for actigraphy data visualization and analysis

The possibility to continuously record locomotor movements using accelerometers (actigraphy) has allowed field studies of sleep and rest-activity patterns. It has also enabled large-scale data collections, opening new avenues for research. However, each brand of actigraph devices encodes recordings in its own format and closed-source proprietary softwares are typically used to read and analyse actigraphy data. In order to provide an alternative to these softwares, we developed a comprehensive open-source toolbox for actigraphy data analysis, pyActigraphy. It allows researchers to read actigraphy data from 7 different file formats and gives access to a variety of rest-activity rhythm variables, automatic sleep detection algorithms and more advanced signal processing techniques. Besides, in order to empower researchers and clinicians with respect to their analyses, we created a series of interactive tutorials that illustrate how to implement the key steps of typical actigraphy data analyses. As an open-source project, all kind of user’s contributions to our toolbox are welcome. As increasing evidence points to the predicting value of rest-activity patterns derived from actigraphy for brain integrity, we believe that the development of the pyActigraphy package will not only benefit the sleep and chronobiology research, but also the neuroscientific community at large.COGNA

pyActigraphy: open-source python package for actigraphy data visualisation and analysis

The pyActigraphy toolbox, an open-source python package for actigraphy data visualisation and analysis, offers functionalities to automatise data pre-processing, read large file batches and implement various metrics and techniques for actigraphy data analysis. By developing the pyActigraphy package, we not only hope to facilitate data analysis but also foster research using actimetry and drive a community effort to improve this open-source package and develop new variables and algorithms.COGNA

Chronic napping alters cognitive performance in healthy older adults

peer reviewe

Herpes simplex virus, early neuroimaging markers and incidence of Alzheimer's disease

While previous studies suggest the implication of herpes simplex virus (HSV) in the onset of Alzheimer's disease (AD), no study has investigated its association with early neuroimaging markers of AD. In the Three-City and the AMI cohorts, the associations between HSV infection and (i) hippocampal volume (n = 349), (ii) white matter alterations in the parahippocampal cingulum and fornix using diffusion tensor imaging (n = 260), and (iii) incidence of AD (n = 1599) were assessed according to APOE4 status. Regardless of APOE4 status, infected subjects presented (i) significantly more microstructural alterations of the parahippocampal cingulum and fornix, (ii) lower hippocampal volumes only when their anti-HSV IgG level was in the highest tercile-reflecting possibly more frequent reactivations of the virus (p = 0.03 for subjects with a high anti-HSV IgG level while there was no association for all infected subjects, p = 0.19), and (iii) had no increased risk of developing AD. Nevertheless, among APOE4 carriers, infected subjects presented lower hippocampal volumes, although not significant (p = 0.09), and a two or three times higher risk of developing AD (adjusted Hazard ratio (aHR) = 2.72 [1.07-6.91] p = 0.04 for infected subjects and aHR = 3.87 [1.45-10.28] p = 0.007 for infected subjects with an anti-HSV IgG level in the highest tercile) while no association was found among APOE4 noncarriers. Our findings support an association between HSV infection and AD and a potential interaction between HSV status and APOE4. This reinforces the need to further investigate the infectious hypothesis of AD, especially the associated susceptibility factors and the possibility of preventive treatments

Fractal regulation of human motor activity, hypothalamic integrity and napping during ageing

editorial reviewedIntroduction: Human activity exhibits a fractal behaviour, characterised by scale-invariant patterns over time scales ranging from minutes to 24 hours. Animal studies have shown that alterations of the suprachiasmatic nucleus (SCN), the circadian pacemaker located in the anterior part of the hypothalamus, are associated with a reduced scale-invariant correlation. Such reduction is also observed in ageing and Alzheimer’s disease, both marked by a loss of SCN integrity. Here, we aimed at assessing the association between fractal regulation and in-vivo hypothalamic integrity in healthy older nappers and no nappers differing in their 24-hour distribution of rest-activity patterns. Methods: 28 healthy elderly nappers and 31 age- and gender matched no-nappers (mean age (±SD): 69.0±5.3 years, 37% female) underwent a 40-h multiple nap constant routine (CR). Locomotor activity was recorded using actimetry during (13±2) days and fractal correlation, αcirca, was calculated using detrended fluctuation analysis. Macromolecular content of grey matter tissue in the anterior inferior region was quantified using MRI derived Magnetization Transfer saturation (MTsat) maps. Results: Group comparison confirmed that the circadian modulation of sleep efficiency during the CR is reduced in nappers, compared to no-nappers (p<0.05). Furthermore, bayesian mixed-effects models indicated that fractal correlation, αcirca, was linked to MTsat values within the anterior inferior hypothalamic region, with napping acting as a modulating factor (MTsat : ß=0.074, HDI(95%)=[0.003, 0.114], MTsat*nap group,ß=-0.091,HDI(95%)=[-0.177,0.002]). Discussion: Our results support the hypothesis that daytime rest is linked to circadian alteration. Furthermore, they reveal for the first time that fractal regulation of locomotor activity is linked to in-vivo assessed integrity of the anterior hypothalamus, encompassing the SCN. Napping and associated circadian alteration seem to mediate this association. Together, these data put forward the functional relevance of fractal regulation as a potential health risk (circadian) indicator.COGNAP3. Good health and well-bein

ENIGMA-Sleep:Challenges, opportunities, and the road map

Neuroimaging and genetics studies have advanced our understanding of the neurobiology of sleep and its disorders. However, individual studies usually have limitations to identifying consistent and reproducible effects, including modest sample sizes, heterogeneous clinical characteristics and varied methodologies. These issues call for a large-scale multi-centre effort in sleep research, in order to increase the number of samples, and harmonize the methods of data collection, preprocessing and analysis using pre-registered well-established protocols. The Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) consortium provides a powerful collaborative framework for combining datasets across individual sites. Recently, we have launched the ENIGMA-Sleep working group with the collaboration of several institutes from 15 countries to perform large-scale worldwide neuroimaging and genetics studies for better understanding the neurobiology of impaired sleep quality in population-based healthy individuals, the neural consequences of sleep deprivation, pathophysiology of sleep disorders, as well as neural correlates of sleep disturbances across various neuropsychiatric disorders. In this introductory review, we describe the details of our currently available datasets and our ongoing projects in the ENIGMA-Sleep group, and discuss both the potential challenges and opportunities of a collaborative initiative in sleep medicine