Evenson Kelly R, Wen Fang, Herring Amy H, Di Chongzhi, LaMonte Michael J, Tinker Lesley Fels, Lee I-Min, Rillamas-Sun Eileen, LaCroix Andrea Z, Buchner David M
Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina - Chapel Hill, Chapel Hill, NC, USA.
Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina - Chapel Hill, Chapel Hill, NC, USA ; Carolina Population Center, University of North Carolina - Chapel Hill, Chapel Hill, NC, USA.
Prev Med Rep. 2015;2:750-756. doi: 10.1016/j.pmedr.2015.08.021.
We conducted a laboratory-based calibration study to determine relevant cutpoints for a hip-worn accelerometer among women ≥60 years, considering both type and filtering of counts.
Two hundred women wore an ActiGraph GT3X+ accelerometer on their hip while performing eight laboratory-based activities. Oxygen uptake was measured using an Oxycon portable calorimeter. Accelerometer data were analyzed in 15-second epochs for both normal and low frequency extension (LFE) filters. Receiver operating characteristic (ROC) curve analyses were used to calculate cutpoints for sedentary, light (low and high), and moderate to vigorous physical activity (MVPA) using the vertical axis and vector magnitude (VM) counts.
Mean age was 75.5 years (standard deviation 7.7). The Spearman correlation between oxygen uptake and accelerometry ranged from 0.77 to 0.85 for the normal and LFE filters and for both the vertical axis and VM. The area under the ROC curve was generally higher for VM compared to the vertical axis, and higher for cutpoints distinguishing MVPA compared to sedentary and light low activities. The VM better discriminated sedentary from light low activities compared to the vertical axis. The area under the ROC curves were better for the LFE filter compared to the normal filter for the vertical axis counts, but no meaningful differences were found by filter type for VM counts.
The cutpoints derived for this study among women ≥60 years can be applied to ongoing epidemiologic studies to define a range of physical activity intensities.
我们开展了一项基于实验室的校准研究，以确定60岁及以上女性髋部佩戴式加速度计的相关切点，同时考虑计数的类型和滤波。
200名女性在进行八项基于实验室的活动时，在髋部佩戴ActiGraph GT3X+加速度计。使用便携式氧代谢仪测量摄氧量。对加速度计数据在15秒时间段内进行分析，包括正常和低频扩展（LFE）滤波器。采用受试者工作特征（ROC）曲线分析，使用垂直轴和矢量大小（VM）计数来计算久坐、轻度（低强度和高强度）以及中度至剧烈身体活动（MVPA）的切点。
平均年龄为75.5岁（标准差7.7）。对于正常和LFE滤波器以及垂直轴和VM，摄氧量与加速度测量之间的Spearman相关性在0.77至0.85之间。与垂直轴相比，VM的ROC曲线下面积通常更高，与久坐和轻度低强度活动相比，区分MVPA的切点的ROC曲线下面积更高。与垂直轴相比，VM能更好地区分久坐和轻度低强度活动。对于垂直轴计数，LFE滤波器的ROC曲线下面积比正常滤波器更好，但对于VM计数，未发现滤波器类型有显著差异。
本研究得出的60岁及以上女性的切点可应用于正在进行的流行病学研究，以定义一系列身体活动强度。
