| BackgroundThe prevalence of overweight and obesity has shown a rapid increase in China. Besides factors of dietary, physical inactivity and sedentary life style already become the key issue. At present, there are no recommendations on appropriate physical activity and leisure sedentary time for preventing overweight and obesity in China. It is important to explore the optimal cut-off of physical activity and leisure sedentary time in order to keep healthy.ObjectivesTo examine the dynamics of physical activity and leisure sedentary time; To recommend the optimal amounts of physical activity and leisure sedentary time for controlling overweight and obesity; To investigate the relationship between the key covariates and the physical activity and leisure sedentary time distribution.MethodsWe used longitudinal data from China Health and Nutrition Survey. According the aims of the study, there were three groups of subjects. The first group included adults aged 18-60 years (N=8,587 men and 9,232 women) between 1991 and 2011 to examine the trends of distribution of physical activity and leisure sedentary time. The second group included adults aged 18-60 years ((N=2,001 men and 2,242 women) between 2004 to 2011 with at least two waves of data collection. Body Mass Index was between 18.5 and 24 in 2004 and later become overweight and obesity. Receiver operating characteristic curve for repeated measures was applied to explore the optimal cut off of physical activity and leisure sedentary time for preventing overweight and obesity. The last group included adults aged 18-60 years ((N=3,752 men and 3,983 women) between 2004 to 2011 with at least two waves of data collection. Separate sex stratified longitudinal quantile regression analyses were used to investigate changes in the physical activity and leisure sedentary time distribution over time.Results1. Physical activity levels in both occupational, domestic and travel physical activity decreased significantly from 1991 to 2011. Leisure physical activity was very low and increased a little. The leisure physical activity of male and female were 5.8MET.h/w and 4.2MET.h/w, respectively, which was far less than the recommendation of Chinese Physical Activity Guideline.2. In 2004, TV and reading time were by far the largest contributors to total leisure sedentary time. However, throughout this 20-year period, total leisure sedentary time increased significantly, especially the computer usage. In 2011, time spending in TV and computer became the main contributors.3. For male adults aged 18-44 years, the optimal cut-off of physical activity was 141.62MET·h/w, and leisure PA was 17.44 MET·h/w for preventing overweight and obesity. And for male adults aged 45-60 years, the the optimal cut-off of physical activity was 158.70 MET·h/w, and leisure PA was 20.72 MET·/w. For female adults aged 18-44 years, the optimal cut-off of physical activity was 199.49 MET·/w, and leisure PA was 11.36 MET·/w for preventing overweight and obesity. And for female adults aged 45-60 years, the the optimal cut-off of physical activity was 188.50 MET·/w, and leisure PA was 23.09 MET·/w.4. For male adults aged 18-44 years, the optimal cut-off of leisure sedentary time was 11.34 h/w for preventing overweight and obesity. And for male adults aged 45-60 years, the the optimal cut-off of leisure sedentary time was 14.04 h/w. For female adults aged 18-44 years, the optimal cut-off of leisure sedentary time was 8.36 h/w for preventing overweight and obesity. And for female adults aged 45-60 years, the the optimal cut-off of leisure sedentary time was 17.16 h/w.5. The tendency of the distribution of physical activity over time was significantly associated with individual and community factors. For male adults, age and marriage status were positively associated with total physical activity. However, education level, income and urbanization index were negatively associated with total physical activity. Age was associated with negatively changes in leisure physical activity in the lower percentile. Marriage status, education level, income and urbanization index were associated with positively changes in leisure physical activity in the lower percentile. For female adults, marriage status and income were positively associated with total physical activity. However, age, education level and urbanization index were negatively associated with total physical activity. Age and marriage status had a negatively association with female leisure physical activity in the lower percentile. Income, education level and urbanization index had a positively association with female leisure physical activity in the lower percentile.6. The dynamics of the distribution of leisure sedentary time over time was also strongly influenced by individual and community factors. Age and marriage status were negatively associated with total leisure sedentary time for both genders. However, education level, income and urbanization index were positively associated with total leisure sedentary time for both genders. For male adults, age and urbanization index were associated with positively changes in television time in the upper percentile. However, marriage status, education level and income were associated with negatively changes in television time in the upper percentile. Income and urbanization index had a positively association with computer usage time in the upper percentile. And age, marriage status and education level had a negatively association with computer usage time in the upper percentile. For female adults, age, marriage status, education level and urbanization index were associated with positively changes in television time in the upper percentile. However, income with negatively changes in television time in the upper percentile. Education level, income and urbanization index had a positively association with computer usage time in the upper percentile. Age and marriage status had a negatively association with computer usage time in the upper percentileConclusionDuring the past two decades, physical activity levels decreased significantly both male and female adults. However, total leisure sedentary time increased significantly. Age, marital status, education level, income level and urbanization were associated with physical activity leisure sedentary time at different percentiles. It is essential to improve physical activity guidelines and develop sedentary behavior guideline and to educate intervention objects to increase PA and decrease leisure sedentary time. |
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