Validation of circadian rhythm parameters derived from a user‐friendly activity monitor for long‐term continuous monitoring of brain health

Abstract

AbstractBackgroundFragmentation of sleep patterns is one of the earliest symptoms of Alzheimer’s disease and related dementias (ADRD) and is debilitating to both patients and caregivers. Interdaily stability and intradaily variability can be used to characterize the strength of an individual’s circadian rhythms. The utility of these parameters could be increased by applying this analysis to activity data collected over long periods, enabling longitudinal studies of changes in circadian rhythms as ADRD progresses.MethodActivity data was collected for seven study participants (mean age = 73 years; 2 men, 5 women) for two weeks each. Over the two week period, participants simultaneously wore an ActiGraph wGT3X‐BT actigraph at the waist and on the nondominant wrist and a Withings Activite watch also on the nondominant wrist. The Withings watch was chosen for our study because of its watch‐like form factor, low cost and long battery life (up to six months). MATLAB functions were written to calculate interdaily stability and intradaily variability from the data collected from all three devices for each participant. Interdaily stability and intradaily variability calculated from the Withings watch data were compared with the same parameters calculated using both data from the actigraph worn on the wrist and the actigraph worn on the waist.ResultEach participant contributed 144 hours of device data. High correlations were found in each of the comparison cases. For interdaily stability, the KS p‐value of correlation between the data produced by the watch and the actigraph was 0.68 for the actigraph at the waist and 0.65 at the wrist. In the case of intradaily variability, the KS p‐value was 0.86 at the waist and 0.92 at the wrist.ConclusionThese results demonstrate the validity of a user‐friendly, low cost, consumer grade activity monitor to generate standard metrics of circadian function (interdaily stability and intradaily variability) in longitudinal studies of circadian rhythms. Low cost mass‐market activity monitors can be a valuable addition to studies of life patterns because they facilitate data collection both over long periods of time and from large numbers of study participants.