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 sleep and circadian rhythms. Actigraphs sense movements using accelerometers. The authors have addressed the following questions. First, they investigated how to filter the accelerometer signal in order to minimize the contribution of accelerations induced by positional changes in the gravitational field. A bandpass filter of 0.5 to 11 Hz appropriately assesses movement induced accelerations while minimizing gravitational artefact. Secondly, the authors have proposed an alternative to traditional methods of signal processing in actigraphy, in order to assess both the duration and intensity of movements, and to discriminate Parkinsonian tremor. Based on this algorithm, a new type of actigraph was designed. The authors have used actigraphy in a series of studies investigating symptom fluctuations and medication responses in Parkinson patients, and circadian rhythm disturbances and possible remedies in elderly and Alzheimer patients