Hypokinesia in Parkinson's disease: influence of age, disease severity, and disease duration

Wearable sensors during drawing tasks to measure the severity of essential tremor

Commonly used methods to assess the severity of essential tremor (ET) are based on clinical observation and lack objectivity. This study proposes the use of wearable accelerometer sensors for the quantitative assessment of ET. Acceleration data was recorded by inertial measurement unit (IMU) sensors during sketching of Archimedes spirals in 17 ET participants and 18 healthy controls. IMUs were placed at three points (dorsum of hand, posterior forearm, posterior upper arm) of each participant's dominant arm. Movement disorder neurologists who were blinded to clinical information scored ET patients on the Fahn-Tolosa-Marin rating scale (FTM) and conducted phenotyping according to the recent Consensus Statement on the Classification of Tremors. The ratio of power spectral density of acceleration data in 4-12 Hz to 0.5-4 Hz bands and the total duration of the action were inputs to a support vector machine that was trained to classify the ET subtype. Regression analysis was performed to determine the relationship of acceleration and temporal data with the FTM scores. The results show that the sensor located on the forearm had the best classification and regression results, with accuracy of 85.71% for binary classification of ET versus control. There was a moderate to good correlation (r2 = 0.561) between FTM and a combination of power spectral density ratio and task time. However, the system could not accurately differentiate ET phenotypes according to the Consensus classification scheme. Potential applications of machine-based assessment of ET using wearable sensors include clinical trials and remote monitoring of patients.

Wearable systems for monitoring mobility-related activities in older people: a systematic review

OBJECTIVE

The use of wearable motion-sensing technology offers important advantages over conventional methods for obtaining measures of physical activity and/or physical functioning in aged individuals. This review aims to identify the actual state of applying wearable systems for monitoring mobility-related activity in older populations. In this review we focus on technologies and applications, research designs, feasibility and adherence aspects, and clinical relevance of wearable motion-sensing technology.

DATA SOURCES

PubMed (MEDLINE since 1990), Ovid (BIOSIS, CINAHL), and Cochrane (Central) and reference lists of all relevant articles were searched.

REVIEW METHODS

Two authors independently reviewed randomized and non-randomized trials on people above 65 years systematically. Quality of selected articles was scored and study results were summarised and discussed.

RESULTS

Two hundred and twenty-seven abstracts were considered. After application of inclusion criteria and full text reading, 42 articles were taken into account in a full text review. Twenty of these papers evaluated walking with step counters, other papers used varying accelerometry approaches for obtaining overall activity measures (n = 16), or for monitoring changes in body postures and activity patterns (n = 17). Seven studies explicitly mentioned feasibility and/or adherence aspects. Eight studies presented outcome evaluations of interventions. Eight articles were representing descriptive research designs, three articles were using mixed descriptive and exploratory research designs, 23 articles used exploratory research-type designs, and eight articles used experimental research designs.

CONCLUSION

Although feasible methods for monitoring human mobility are available, evidence-based clinical applications of these methods in older populations are in need of further development.

Evaluation of ActiTrac (ambulatory activity monitor) in Parkinson's Disease

At present, the evaluation of Parkinson's Disease (PD) relies mainly on Unified Parkinson's Disease Rating Scale (UPDRS). Other objective measures have been proposed, including functional studies, timed tests and ambulatory activity monitors (AAM). We carried out a prospective study to analyze the utility and correlation of the AAM: ActiTrac with UPDRS scores and timed tests in patients with PD. We studied 28 patients with idiopathic PD (age: 62 +/- 11 years; duration of illness: 7.7 +/- 4.4 years; clinical stage 2.3 +/- 0.39). Motor evaluation included UPDRS and five timed tests: Purdue Pegboard test and those proposed in CAPIT protocol, pronation-supination (PS), finger dexterity (FD), movement between two points (MTP) and walking test (WT). Clinical evaluation was performed in off condition, at 9 a.m., (12h off their medication). Finally, ActiTrac was placed on the wrist (more affected side) continuously for at least 72h. ActiTrac activity was correlated (Spearman) with total UPDRS (r: - 0.53, p < 0.005) and motor UPDRS (r:- 0.46, p: 0.01); UPDRS rigidity subscore (r:- 0.52, p < 0.01); UPDRS bradykinesia subscore (r:- 0.48; p:0.01); FD (r: - 0.47 p: 0.01), WT (r: - 0.49, p < 0.01) and Purdue test (r:0.54; p < 0.01). ActiTrac seems to be a reasonably accurate method to evaluate motor activity in PD.

New actigraph for long-term tremor recording

A new method of movement analysis is validated, allowing an actigraph to discriminate tremor from other movements and store duration and intensity measures of both movement types. For algorithm optimization, wrist acceleration was recorded in nine controls and nine Parkinson's disease patients, while simultaneously rating their observed tremor minute by minute on item 20 of the Unified Parkinson's Disease Rating Scale. An optimization procedure to minimize false positives in controls while maximizing tremor detection in patients resulted in false positive tremor classification in 2.4% +/- 2.5% of the movement time of control subjects (range, 0%-7%), while providing tremor classification in 82.1% +/- 15.4% of the movement time in patients (range, 55%-100%), correlating r = 0.93 with their averaged observed tremor score. A second, generalizability study showed that application of the optimized algorithm resulted in accurate classification of 71% +/- 14% of the observed tremor time (range, 46%-90%) in another 9 patients and in a false positive classification in only 0.5% +/- 0.8% of the time in another 10 controls (range, 0%-2.4%). The commercial availability of this actigraph now for the first time makes it possible to investigate tremor fluctuations over several weeks. An example is given of how long-term monitoring can be of use in evaluation of symptom management.

Evaluation of timed tests in advanced Parkinsonian patients who were candidates for subthalamic stimulation

The evaluation of Parkinson disease relies on the use of clinical scales, mainly the UPDRS. However, especially for those candidates for functional surgery, other objective methods are also considered, including the use of timed tests.

METHODS

The authors studied the motor performance of 33 patients with advanced Parkinson disease (PD) who were candidates for subthalamic nucleus (STN) stimulation. Presurgical motor evaluation included UPDRS and the 4 timed tests of the CAPIT protocol, including pronation-supination (PS), finger dexterity (FD), movement between 2 points (MTP), and the walking test (WT). A clinical evaluation was performed during patients' OFF condition and during their best ON state. Fifteen patients were implanted with STN stimulation and were evaluated at 6 months with the same protocol described for the presurgical evaluation.

RESULTS

At baseline, all 4 timed tests significantly correlated with total and motor UPDRS scores, in the OFF and ON states, especially MTP. All timed tests, save WT, significantly improved after surgery in the OFF state (especially MTP; P = 0.002). After surgery, all timed tests, save FD, significantly correlated with total and motor UPDRS scores in the OFF state. Timed tests, especially MTP, maintained an excellent correlation with UPDRS in both OFF and ON states before and after surgery.

Quantitative assessment of daytime motor activity provides a responsive measure of functional decline in patients with Huntington's disease

Voluntary motor impairment is a functionally important aspect of Huntington's disease (HD). Therefore, quantitative assessment of disturbed voluntary movement might be important in follow-up. We investigated the relation between quantitatively assessed daytime motor activity and symptom severity in HD and evaluated whether assessment of daytime motor activity is a responsive measure in the follow-up of patients. Sixty-four consecutive HD patients and 67 age- and sex-matched healthy controls were studied. Daytime motor activity was recorded using a wrist-worn activity monitor that counts all movements during a period of five consecutive days. Patients were rated clinically for voluntary motor impairment, dyskinesias, posture & gait, depression, cognitive impairment and functional capacity. Follow-up was available from 40 patients (mean follow-up 2.0 years) and 29 controls (mean follow-up 5.9 years). Despite chorea, patients had less daytime motor activity than controls (P < 0.005). This hypokinesia correlated with impaired voluntary movements (r = 0.37; P < 0.01), disturbed posture & gait (r = 0.38; P < 0.005) and especially with reduced functional capacity (r = 0.51; P < 0.0005). During follow-up, hypokinesia remained unchanged in clinically stable patients, but became worse in those whose functional disability progressed (P < 0.005). Hypokinesia seems a core symptom of HD which is related to functional capacity. Actimetric assessment of hypokinesia is responsive to disease progression and can be used as an objective tool for follow-up.

Ambulatory quantitative assessment of body position, bradykinesia, and hypokinesia in Parkinson's disease

We used ambulatory monitoring to quantify body position, bradykinesia, and hypokinesia simultaneously in 50 patients with Parkinson's disease (PD) and 43 healthy elderly during the diurnal period. Reliable automatic detection of three defined body positions proved possible. As compared with controls, PD patients spent less time upright and more time during the day lying down, which correlated well with the self-reported time spent lying down. PD patients had significantly lower mean values of extremity acceleration and higher mean values of immobility than controls. The objective measures of bradykinesia and hypokinesia showed only a modest or no relation to the semiquantitative subjective Unified Parkinson's Disease Rating Scale (UPDRS) motor scores, which most likely was due to differences between the methods. In contrast to bradykinesia measures, hypokinesia measures showed clear sex differences in both patients and controls. Over time, trunk and arm movements occurred more frequently in women than in men. Our ambulatory monitoring assessment disclosed clinically relevant information about the mobility profile and offers a way to quantify cardinal movement features simultaneously in PD patients throughout the day.

Actigraphic monitoring of movement and rest-activity rhythms in aging, Alzheimer's disease, and Parkinson's disease

Actigraphy, the long-term assessment of wrist movements, is used in several research fields, among which are included sleep and circadian rhythms. Actigraphs record movements using accelerometers. The present paper addresses some basic problems and their solutions in the actigraphic assessment of movement, motor symptoms, circadian rest-activity rhythms, and nocturnal agitation in healthy elderly and elderly suffering from a neurodegenerative disease (i.e., Parkinson's disease or Alzheimer's disease) and summarizes the results of previous and ongoing research. First, we have investigated how to filter the accelerometer signal in order to minimize the contribution of accelerations induced by positional changes in the gravitational field--a strong source of artefacts. A bandpass filter from 0.5 to 11 Hz appropriately assesses movement induced accelerations while minimizing gravitational artefact. The application of a bandpass filter from 0.25 to 2 or 3 Hz, as is used in some of the commercially available actigraphs, results in artefacts and moreover biases the slower part of the movement spectrum. It is therefore far from optimal for research on aging, which is associated with a generalized motor slowing. Second, we have proposed an alternative to traditional methods of signal processing in actigraphy, in order to assess both the duration and intensity of movements, and in order to distinguish Parkinsonian tremor. Based on this algorithm, new types of actigraphs have been designed. Third, we have proposed sensitive variables in order to quantify rest-activity rhythm disturbances in healthy elderly subjects and Alzheimer patients, who often present with symptoms of nocturnal restlessness. Since, in these subjects, research protocols applying enforced phase shifts or time-free environments are unfeasible and not justifiable from an ethical point of view, the variables were specifically designed to assess the functionality of the circadian timing system from actigraphic recordings made in the natural environment of subjects. Examples of the application of actigraphy are given, including studies on symptom fluctuations and medication responses in Parkinson patients, and studies on circadian rhythm disturbances and possible remedies in elderly and Alzheimer patients.

Quantitation of lower physical activity in persons with multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that often affects the motor system. We tested the hypothesis that physical activity was lower in a group of 17 MS patients (mean +/- SD; age = 46 +/- 6 yr, 11 females, 6 males) compared with 15 healthy sedentary control subjects (age = 44 +/- 7 yr, 9 females, 6 males). Physical activity was measured with a three-dimensional accelerometer and with an activity questionnaire for 7 d. Vector magnitude values from the accelerometer for the MS and sedentary control subjects were 121,027 +/- 59,336 and 185,892 +/- 60,566 arbitrary units/day, respectively (P = 0.01). Estimated energy expenditure values derived from the questionnaire were 35.9 +/- 3.0 and 36.2 +/- 4.1 Kcal.kg-1.d-1 (NS), respectively. Thus, when measured directly with an accelerometer, activity was lower in MS compared with sedentary control subjects. The data also suggest that the accelerometer was more sensitive than the questionnaire for detecting differences in activity between two relatively sedentary populations, including one with neurologic disease.

Gravitational artefact in frequency spectra of movement acceleration: implications for actigraphy in young and elderly subjects

Actigraphy, the long-term assessment of wrist movements by means of a small solid-state recorder, is widely used in a variety of human research fields, among which sheep, circadian rhythms and aging. Actigraphs assess movement with the use of accelerometers, which sense accelerations resulting from muscle force as well as accelerations due to changes in the position of the sensor in the gravitational field. In the present paper a method is described to minimise gravitational artefact in movement assessment by calculating the instantaneous acceleration vector from 3 perpendicular acceleration signals. It is shown that the power spectra of single axis acceleration signals are dominated by low-frequency components (+/- 0.25 Hz) due to gravitational artefact. Spectra of the instantaneous acceleration vector indicate that 'true' movement accelerations resulting from muscle force are present in a much wider range: from 0.25 to 11 Hz. Wrist accelerations in elderly subjects were found to be of lower amplitude and frequency as compared to young subjects. It is furthermore shown that a bandpass filter of 0.25 to 2 or 3 Hz, as has been used in commercially available actigraphs, is far from optional, and may even result in a positive bias for movement detection in the elderly. This bias may underly contradictory findings in actigraphic studies on human aging. When a bandpass filter of 0.5-11 Hz is applied to a single-axis acceleration signal, the influence of gravitational artefact and bias are minimized, and the age-related decline in activity is properly detected.