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78
a uniaxial accelerometer that measures acceleration in the vertical plane and it has been
shown as a valid and reliable measure of physical activity for children and
adolescents.(169) The participants were instructed to wear the device on the right hip
during waking hours, with the exception of time spent in bathing or swimming activities.
Accelerometer data were downloaded and processed using a SAS program developed for
use with NHANES physical activity monitor data (available at:
http://riskfactor.cancer.gov/tools/nhanes_pam). The raw data is processed to calculate the
minutes of non-wear (defined by an interval of sixty or more consecutive minutes of zero
activity intensity counts, with exceptions for up to 3 minutes of 0-100 counts) and the
minutes of wear time.
Although participants were instructed to wear the accelerometers for seven
consecutive days, the wear time varied. In keeping with prior research,(130, 204) a valid
day of wear was defined as having at least ten hours of wear-time, and only participants
with four or more valid days of data were included in the analyses. The total number of
minutes spent in moderate-to-vigorous physical activity (MVPA) and sedentary activity,
was determined by summing minutes in a day where the count met the criterion for that
intensity. Then, these total minutes were averaged across the number of valid days to
obtain the mean minutes per day. The cut point for MVPA [ 4 metabolic equivalent
(METs)] was age-adjusted using the criteria from the Freedson group.(206) The
sedentary cut point of 100 counts, which was previously defined by Matthews et al.,(129)
has been validated in adolescents.(203)
Object Description
| Title | The vicious cycle of inactivity, obesity, and metabolic health consequences in at-risk pediatric populations |
| Author | Hsu, Ya-Wen |
| Author email | ywxxbirdy@yahoo.com; yawenhsu@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Preventive Medicine (Health Behavior) |
| School | Keck School of Medicine |
| Date defended/completed | 2011-03-09 |
| Date submitted | 2011 |
| Restricted until | Restricted until 26 Apr. 2012. |
| Date published | 2012-04-26 |
| Advisor (committee chair) |
Chou, Chih-Ping Spruijt-Metz, Donna |
| Advisor (committee member) |
Unger, Jennifer B. Azen, Stanley Paul Palinkas, Lawrence A. |
| Abstract | PURPOSE: This dissertation examined the associations between physical activity, sedentary behavior, overweight, and the metabolic syndrome (MetS) in at-risk pediatric populations in the United States and in China. Study 1 identified the independent influences of physical activity, sedentary behavior, and other weight-related correlates on overweight status in Chinese youth. Study 2 explored the influences of physical activity and sedentary behavior on MetS in US minority youth. Study 3 compared the longitudinal trends of physical activity and sedentary behavior between youth with and without MetS in a sample of US minority female youth.; METHODS: Participants were youth (ages 8-18 years) in the United States and in China. Study 1 used baseline data from of a longitudinal smoking prevention and health promotion study conducted in the 7 large cities in China for Chinese youth ages 11-18 years. Study 2 used baseline data from three related pediatric obesity studies that share a set of common methods and measures (US Latino and African American youth ages 8-18 years). Data for Study 3 are from a longitudinal, observation study for Latina and African American female youth ages 8-11 years at baseline.; RESULTS: In Study 1, Chinese youth were more likely to be overweight if they spent more time being sedentary, slept <7 hours/night, were male, were younger, participated more in vigorous physical activity, had higher levels of parental education, better self-perceived health status, a higher frequency of vegetable intake, and a lower frequency of sweet/fast food intake. In Study 2, lower levels of moderate-to-vigorous physical activity (by accelerometry) and higher levels of sedentary behavior (by 3-day physical activity recall) are associated with increased the metabolic risk independent of each other and body composition. In Study 3, a significant decline in MVPA and an increase in sedentary behavior were observed over one year. Sedentary behavior as measured by accelerometry increased 23.42 minutes/per quarterly visit, adding up to 93.68 minutes/per year more in youth with MetS than in those without.; CONCLUSION: Overweight-related correlates seem to play different roles in the Chinese culture than in Western cultures. Findings from this dissertation support a vicious cycle of increasing inactivity, obesity, and metabolic complications. These findings, coupled with longitudinal evidence of the effects of activity levels on obesity and MetS, suggests that physical activity and sedentary behavior could function as antecedents as well as consequences of overweight or MetS in youth. |
| Keyword | Chinese youth; metabolic syndrome; minority youth; obesity; physical activity; sedentary behavior |
| Geographic subject (country) | USA; China |
| Coverage date | 1970/2010 |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m3779 |
| Contributing entity | University of Southern California |
| Rights | Hsu, Ya-Wen |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Hsu-4455 |
| Archival file | uscthesesreloadpub_Volume23/etd-Hsu-4455.pdf |
Description
| Title | Page 89 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 78 a uniaxial accelerometer that measures acceleration in the vertical plane and it has been shown as a valid and reliable measure of physical activity for children and adolescents.(169) The participants were instructed to wear the device on the right hip during waking hours, with the exception of time spent in bathing or swimming activities. Accelerometer data were downloaded and processed using a SAS program developed for use with NHANES physical activity monitor data (available at: http://riskfactor.cancer.gov/tools/nhanes_pam). The raw data is processed to calculate the minutes of non-wear (defined by an interval of sixty or more consecutive minutes of zero activity intensity counts, with exceptions for up to 3 minutes of 0-100 counts) and the minutes of wear time. Although participants were instructed to wear the accelerometers for seven consecutive days, the wear time varied. In keeping with prior research,(130, 204) a valid day of wear was defined as having at least ten hours of wear-time, and only participants with four or more valid days of data were included in the analyses. The total number of minutes spent in moderate-to-vigorous physical activity (MVPA) and sedentary activity, was determined by summing minutes in a day where the count met the criterion for that intensity. Then, these total minutes were averaged across the number of valid days to obtain the mean minutes per day. The cut point for MVPA [ 4 metabolic equivalent (METs)] was age-adjusted using the criteria from the Freedson group.(206) The sedentary cut point of 100 counts, which was previously defined by Matthews et al.,(129) has been validated in adolescents.(203) |
