Objectives: The purpose of the study was to test (1) equivalence and stability of the Actiwatch-Score (Mini Mitter, Bend, OR) and (2) the range of activity counts under controlled laboratory conditions. Actigraphy is frequently used as an objective measure of activity/rest in various populations. The student’s mentor is evaluating the Actiwatch-Score for that purpose in ambulatory women. Although reports of biometric performance of actigraphy are available, none were found that evaluated the equivalence and stability of the Actiwatch-Score.
Methods: A 21-minute activity/rest protocol was developed by the student to test stability (intra-instrument) and equivalence (inter-instrument) reliability estimates of activity counts obtained with two Actiwatch-Score actigraphs. The student wore the actigraphs and performed the activity/rest protocol steps. The mentor was the timekeeper. All testing was done consecutively over a 1 ½ -hour time period with 10-minute rest periods between each testing session. Data were recorded in 30-second epochs. Data were downloaded and imported into a spreadsheet for inspection. A 5 ½ -minute portion of the protocol was missing for one testing session of one actigraph; therefore, the data from all testing periods were edited so that aligned time series could be compared. Descriptive statistics and Pearson Product-Moment correlation coefficients were computed.
Results: Data points for each data set varied from 28 to 31. All data sets showed a great deal of variability, and were positively skewed. The protocol yielded activity counts from 0 to 4,982/minute. Strong intra-instrument correlations were demonstrated (r = 0.94 for actigraph 1, r = 0.90 for actigraph 2). Likewise, strong inter-instrument correlations were found (r = 0.93 and 0.94).
Conclusions: The two Actiwatch-Score actigraphs tested showed evidence for adequate stability and equivalence reliability under controlled laboratory conditions. The findings suggest that, across a range of activity counts from 0 to nearly 5,000, these actigraphs provide reproducible data.
Back to Rising Stars of Scholarship and Research
Back to 37th Biennial Convention - Scientific Session
Sigma Theta Tau International