Background: A physically inactive lifestyle is associated with an increased risk for a variety of chronic diseases and health conditions. One population at greatest risk of physical inactivity is older adults.
Studies: The specific aims for my dissertation research focused on further development of the Actigraph accelerometer to measure physical activity in community dwelling older adults. I proposed to first further define what an activity count from the Actigraph accelerometer represents. By comparing Actigraph counts to raw accelerometry, oxygen consumption and pedometer step count data at usual and slow walking speeds we found that counts per second were correlated with raw accelerometry and energy cost. Actigraph counts, raw acceleration, pedometer step counts and oxygen consumption were higher for usual versus slow walking conditions as expected. We were able to formulate a regression equation to estimate energy cost from Actigraph counts in community dwelling older adults. For the next project, I investigated the reliability and validity of the various ways to present data from the Actigraph accelerometer. All Actigraph measurement units of interest were highly correlated with each other as well as with performance based measures of mobility, function, age and self reported physical activity. Actigraph counts per minute and standard deviations of counts were able to distinguish between low and high mobility and functioning groups. Using ROC curves, we established a cut off value of 150 counts per minute to detect mobility and function problems. Finally, I determined meaningful change values of physical activity measured by the Actigraph over a 12 week exercise intervention in community dwelling older adults with walking difficulty. We found a value of 30 counts per minute to indicate substantial change beyond spurious error. Actigraph counts per minute did not change over the course of exercise intervention. However, people who were more active at baseline exhibited improvements in mobility and functional measures compared to those who were less active at baseline.
Conclusion: From the projects described above, Actigraph counts have been validated in older adults against raw accelerometry, oxygen consumption, mobility, function, and self-reported physical activity measures. Inter-rater reliability was excellent for the multiple outputs of the Actigraph accelerometer. Actigraph counts per minute data output is our recommendation since it is the default output, has the least amount of processing, produces high inter-rater reliability and validity against mobility and function.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-07302008-160330 |
| Date | 08 September 2008 |
| Creators | Talkowski, Jaime Berlin |
| Contributors | Jessie VanSwearingen PhD PT FAPTA, Jennifer Brach PhD PT, Subashan Perera PhD, Stephanie Studenski MD MPH, Rakie Cham PhD |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-07302008-160330/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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