A new study published in the International Journal of Behavioral Nutrition and Physical Activity has found that levels of physical activity for adults in China fell by nearly half between 1991 and 2011. Researchers from the University of North Carolina at Chapel Hill, USA, and Shanghai Municipal Center for Disease Control and Prevention, China, report that the decline was more pronounced in women than in men and each new generation had lower activity levels than the previous one.
Although the data suggested that younger men had higher physical activity levels than older men at baseline (in 1991), levels tended to fall as people aged. Physical activity levels for women aged between 25 and 48 years were similar at baseline, but then declined across all age groups more sharply than for men. The difference in the decline for males and females might be explained by the changing role of women, who now spend less time in domestic activities, like preparing food, doing laundry and looking after children whereas the domestic roles of men remain unchanged.
Living in urban areas and owning a car, a TV or a computer were associated with lower levels of physical activity, as were higher education levels or being overweight, the authors show. People in professional jobs, such as doctors, lawyers or architects, showed lower physical activity levels than people in other occupations. Owning a bicycle, being married and larger household sizes were associated with higher physical activity levels.
The researchers used survey data on 13,245 Chinese adults who were between 20 and 59 years old in 1991. Data were collected on nine occasions between 1991 and 2011 as part of the China Health and Nutrition Survey (CHNS). The sample is from nine Chinese provinces and three megacities and is representative of rural, urban and suburban areas that vary in geography, economic development, public resources and health indicators such as life expectancy or obesity rates.
The study concluded that new health policies and public health measures are urgently needed to address the issue of declining physical activity levels which are associated with a rise in overweight and obesity. Jiajie Zang at the Shanghai Municipal Center for Disease Control and Prevention, lead author of the study, said: “Lack of physical activity contributes to between 12-19% of the five major non-communicable diseases in China. These trends are highly relevant for health policy and preventative health measures in China and other countries that are now facing similar challenges.”
Shu Wen Ng, the corresponding author at University of North Carolina at Chapel Hill, said: “Our findings highlight the importance of continued investments that will require ‘whole-of-government’ as well as ‘whole-of-society’ approaches to promote active lifestyles from a young age. Otherwise, previous research indicates that the financial burden of non-communicable diseases is likely to be enormous for both individuals and the country as a whole.”
The study did not examine physical activity in isolation, but instead analyzed changing levels of physical activity in the context of the effects of both age and China’s modernization. The researchers examined age, period and cohort effects. Age effects describe changes in the physical activity of individuals over time as they grow older, period effects describe changes in physical activity across the whole population over time, while cohort effects describe how period effects vary, for example, in a certain age group.
Shu Wen Ng said: “We expected to see the overall reduction in physical activity at work and at home over time, especially among women. That has been documented before. What was interesting was learning that these changes were driven not just by aging, but also a combination of period and cohort effects. People in younger cohorts are starting with lower activity levels to begin with and will continue to reduce their physical activity from an already relatively low point, resulting in an increasing number of Chinese adults who have low physical activity levels and who are likely to lower them further over time.”
Information about travel and active leisure activities was not available until 1997, while information on sedentary leisure activities like watching TV was not collected until 2004. As a result of these data limitations, the researchers focused on physical activity at work and in the home, for which information was available for all 20 years of the survey period. The researchers suggest that it would be important to consider the role of leisure-time activity in future analyses.
Finally, the authors acknowledge some limitations of this observational study, including possible mis-reporting of self-reported work and domestic activity together with a reliance on metabolic equivalent (MET) values from the US, which may not be appropriate for a Chinese population. MET values express the energy cost of physical activities, as derived from a sample of people.
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Notes to editor:
1. Age, period and cohort effects on adult physical activity levels from 1991 to 2011 in China
Jiajie Zang and Shu Wen Ng
International Journal of Behavioral Nutrition and Physical Activity 2016
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