Sleep/wake detection based on cardiorespiratory signals and actigraphy

We investigated the potential of adding cardiac and respiratory activity information to actigraphy for sleep-wake staging. A dataset of 35 recordings with full polysomnography and actigraphy was used to assess the performance of an automated sleep/wake Bayesian classifier using electrocardiogram, inductance plethysmogram estimate of respiratory effort and actigraphy. The best performance was achieved with the linear discriminant model that provided an agreement of Cohen's kappa=0.62 for one of the configurations of the classifier, corresponding to an accuracy of 86.8%, a sensitivity of 66.9% and a specificity of 93.1%. It shows that combining different vital signs for a home sleep-wake staging system could be a promising approach.

Monitoring of drowsiness and microsleep

An overview is presented of different studies on monitoring and detection of drowsiness and microsleep (MS) during driving simulation.

Idiopathic hypersomnia: clinical features and response to treatment

OBJECTIVE

A recent American Academy of Sleep Medicine publication identified a need for research regarding idiopathic hypersomnia. We describe various clinical and polysomnographic features of patients with idiopathic hypersomnia, with an emphasis on response to pharmacotherapy.

METHODS

A retrospective review of our database initially identified 997 patients, utilizing "idiopathic hypersomnia", "hypersomnia NOS", and "primary hypersomnia" as keywords. The charts of eligible patients were examined in detail, and data were abstracted and analyzed. Response to treatment was graded utilizing an internally developed scale.

RESULTS

Eighty-five patients were ultimately identified (65% female). Median (interquartile range) ages of onset and diagnosis were 19.6 (15.5) and 33.7 (15.5), respectively. During a median follow-up duration of 2.4 (4.7) years, 65% of patients demonstrated a "complete response" to pharmacotherapy as assessed by the authors' grading schema. Methylphenidate was most commonly used as a first-line agent prior to December 1998, but subsequently, modafinil became the most common first drug. At the last recorded follow-up visit, 92% of patients were on monotherapy, with greater representation of methylphenidate versus modafinil (51% vs. 32%). Among these patients, methylphenidate produced a higher percentage of "complete" or "partial" responses than modafinil, although statistical significance was not reached (38/40 [95%] vs. 22/25 [88%], respectively, p = 0.291).

CONCLUSIONS

The majority of patients with idiopathic hypersomnia respond well to treatment. Methylphenidate is chosen more often than modafinil as final monotherapy in the treatment of idiopathic hypersomnia, despite the fact that it is less commonly used initially. Further prospective comparisons of medications should be explored.

Comparison of load cells and wrist-actigraphy for unobtrusive monitoring of sleep movements

Accurate assessment of mobility in bed presents challenges to clinicians and researchers alike. Mobility is traditionally assessed by either overnight polysomnograph recording or wrist actigraphy. This paper describes an alternative system for unobtrusive and continuous monitoring of sleep movements that uses load sensors installed at the corners of a bed. This work is focused on the detection and classification of clinically relevant types of movement based on the forces sensed by load cells. The accuracy of the system for detecting movement has been evaluated using data collected in a laboratory setting. We also present a comparison of the proposed system with wrist-actigraphy.

Comparison of the ActiGraph accelerometer and Bouchard diary to estimate energy expenditure in Spanish adolescents

INTRODUCTION

The aim of this study was to evaluate the agreement between the ActiGraph accelerometer and the Bouchard diary to estimate energy expenditure (EE) in a Spanish adolescent population.

METHODS

Sixty-one Spanish adolescents, aged 12-16 years, were recruited for this study. The Bouchard diary and the ActiGraph were administered for 3 consecutive days. EE estimated by the Bouchard diary was calculated using 2 different MET category values (BD-Bouchard and BD-Bratteby). EE estimated by the ActiGraph was calculated using 3 predictive equations (AC-Trost, AC-Freedson, and AC-Ekelund). Participants with complete 24 h data were also analyzed to control the possible loss of accuracy. Agreement was examined by Pearson and concordance correlations, paired t-test, and Bland-Altman method.

RESULTS

Thirty-seven adolescents were included in the analyses with complete 72 h. Relationships between EE calculated by the Bouchard diary and the ActiGraph were high (ranged: r = 0.61-0.78). Concordance correlations were moderate (r c = 0.60) by BD-Bratteby and AC-Trost, and low using BD-Bratteby and AC-Ekelund (r c = 0.15). EE estimated by BD-Bratteby and AC-Trost also showed no significant differences (P> 0.05) and absolutely agree 0.0 +/- 5.0 MJ/d (95% confidence interval: +/- 0.90 MJ/d), but with wide limits of agreement (+/- 9.80 MJ/d). Relationships were higher and differences were smaller in the 72 h sample than in the 24 h sample.

CONCLUSIONS

The Bouchard diary and the ActiGraph showed high relationships, moderate concordance, and large differences to estimate EE in Spanish adolescents. Advantages, disadvantages, and agreements between both instruments must be taking into consideration for health-related research.

Working memory capacity is decreased in sleep-deprived internal medicine residents

BACKGROUND

Concerns about medical errors due to sleep deprivation during residency training led the Accreditation Council for Graduate Medical Education to mandate reductions in work schedules. Although call rotations with extended shifts continue, effects on resident sleep-wake times and working memory capacity (WMC) have not been investigated.

OBJECTIVES

The objective of this study was to measure effects of call rotations on sleep-wake times and WMC in internal medicine residents.

METHODS

During 2 months of an internal medicine training program adhering to ACGME work-hour restrictions (between April 2006 and June 2007), residents completed daily WMC tests, wore actigraphy watches, and logged their sleep hours. This observational study was conducted during a call month requiring 30-hour call rotations every fourth night, whereas the noncall month, which allowed sleep/wake cycle freedom, was used as the control.

MAIN OUTCOME MEASURES

Sleep hours per night and WMC testing.

RESULTS

Thirty-nine residents completing the study had less sleep per night during their call month (6.4 vs 7.3 h per night noncall, p < 0.001) and sleep per night varied from 3.7 to 10.1 hours. Call rotation caused greater self-assessed sleepiness and reduced WMC recall scores (-2.6/test, p < 0.05), and more math errors occurred when on call (+1.07/test, p < 0.04). Full recovery of WMC did not occur until the fourth day after call. On-call rotation on the first month had a confounding detrimental effect on WMC.

CONCLUSION

A month of call rotations reduced overall sleep per night; sleep hours per night were variable, and WMC was adversely affected. Decreased WMC could explain impaired judgment during sleep deprivation, although clinical error rates were not evaluated.

Mobile tools for home-based cardiac rehabilitation based on heart rate and movement activity analysis

Cardiac rehabilitation programs are traditionally carried out in hospitals and health centers under the direct personal supervision of mentoring clinicians. Patient barriers, such as time constraints and distance from treatment centers, have lead to poor uptake of programs among eligible patients. To overcome these barriers, home-based care models have been proposed as a viable alternative to hospital-based cardiac rehabilitation programs. We have developed a measurement system and software tools on a mobile phone platform enabling patients to participate in a home-based cardiac rehabilitation exercise program. A mobile application, TuneWalk, gives guidance to the patients during home exercises using heart rate and physical activity analysis and also stores long-term information about their progress during the weeks of the rehabilitation program. The measured data are also sent to a server for remote exercise performance analysis and consultation by the patient's personal mentor.

Analyzing 180 degrees turns using an inertial system reveals early signs of progression of Parkinson's disease

Changes in turning are one of the early motor deficiencies in Parkinson's Disease (PD). We have proposed a system based on wearable, inertial sensors and a novel automatic analysis algorithm that can assess 180 degrees turns. Twelve patients in early stages of PD and 14 age-matched healthy subjects were enrolled in this study. Inertial sensors were attached on shanks and sternum. Measurement protocol included walking on a straight pathway, turning 180 degrees and returning back. Subjects were measured 4 times, once every 6 months during an 18 months period. At the baseline, 9 subjects from each group repeated the test twice to assess test-retest reliability. Patients with mild PD had a very low Postural Instability Gait Difficulty (PIGD subscore of UPDRS III) score (average 0.67, min 0, max 3). The analysis showed that the patients had a significantly longer turning duration (2.18+/-0.43 vs. 1.79+/-0.27 seconds, p<0.02) and longer delay in their last step before initiating a turn (0.56+/-0.04 vs. 0.52+/-0.04 seconds, p<0.03). Estimated turning duration and other metrics had a high test-retest reliability (rho>0.85). Turning duration also showed a significant Group *Time interaction (p<0.03) during the longitudinal study highlighting early signs of the progression of the disease.

Testing an in-home gait assessment tool for older adults

In this paper, we present results of an automatic vision-based gait assessment tool, using two cameras. Elderly residents from TigerPlace, a retirement community, were recruited to participate in the validation and test of the system in scripted scenarios representing everyday activities. The residents were first tested on a GAITRite mat, an electronic walkway that captures footfalls, and with inexpensive web cameras recording images. The extracted gait parameters from the camera system were compared with the GAITRite; excellent agreement was achieved. The residents then participated in the scenarios, with only the cameras recording. We found that the residents displayed different gait patterns during the realistic scenarios compared to the GAITRite runs. This finding provides support of the importance and advantage of continuous gait assessment in a daily living environment. Results on 4 elderly participants are included in the paper.

Rate estimation for the monitoring of rehabilitation exercises

This study investigates the rate estimation problem encountered in rehabilitation exercise monitoring by using noninvasive portable sensors. The purpose of this paper has two main parts. The first part is to find suitable approaches for the rate detection of tri-axial accelerometer (TA) signals and ECG signals respectively. It is found that the integral type approaches (the average magnitude difference function (AMDF) and autocorrelation function (ACF)) are particularly suitable for TA signal pre-processing, while differential type approaches are very efficient for electrocardiographic (ECG) signal pre-processing. The second part is to develop a square wave matching method to detect the rate from the pre-processed signals. Experimental results indicate that the proposed methods can effectively detect pace rate from TA and heart rate from ECG and remove undesirable spikes.

Behavioral sleep in captive owl monkey (Aotus azarae) and squirrel monkey (Saimiri boliviensis)

The objective of this study was to test the hypothesis that activity-behavioral sleep parameters differ between nocturnallyactive owl monkeys and diurnally-active squirrel monkeys which are sympatric and of Bolivian origin. The total sleep time (TST) and sleep episode length (SEL) of 7 adult owl monkey siblings and 4 adult squirrel monkeys were quantitated by actigraphy for 7 days under captive conditions. The higher TST/24 h values and longer SEL/12 h quiescent phase quantitated for owl monkeys in comparison to that of squirrel monkeys clearly indicate that the behavioral sleep is markedly different between these two groups, though they are sympatric in wild. Significant differences noted in the sleep architecture between squirrel monkeys and owl monkeys can be attributed to the influences in the selected sleep niche, threat perception from predators, and disturbances from natural elements (especially rain) in the natural habitat.

Dynamic activity classification based on automatic adaptation of postural orientation

We propose a dynamic activity classification system with tri-axial accelerometer sensor using adaptation of user's postural orientation. In general, the sensor module is worn at a fixed position such as waist, head, wrist, thigh, and so on. However, in reality, the tilt of the attached sensor could be changed from time to time in actions such as sitting down, standing up, lying, walking or running. Moreover, most of the users want to wear the sensor at their own favorite positions instead of a recommended position. In these cases, the activity detection methods based on fixed tilt value may produce serious problem in their performance. Therefore, we propose a user adapted activity classification method which enables users to freely wear the sensor everywhere on their torso. In order to decide tilt values corresponding user's postural orientation, we focused on tilt-free activities such as walking and running. While walking, the algorithm tries to modify the predefined reference tilt values for the three axes, X, Y and Z. From an experiment, we have achieved 88% of the activity classification accuracy even though the tilt angle is changed while wearing sensors.