The China Health and Nutrition Survey (CHNS), an ongoing international collaborative project between the Carolina Population Center at the University of North Carolina at Chapel Hill, the National Institute of Nutrition and Food Safety, and the Chinese Center for Disease Control and Prevention, was designed to examine the effects of the health, nutrition, and family planning policies and programs implemented by national and local governments and to see how the social and economic transformation of Chinese society is affecting the health and nutritional status of its population. The impact on nutrition and health behaviors and outcomes is gauged by changes in community organizations and programs as well as by changes in sets of household and individual economic, demographic, and social factors.
The survey was conducted by an international team of researchers whose backgrounds include nutrition, public health, economics, sociology, Chinese studies, and demography. The survey took place over a three-day period using a multistage, random cluster process to draw a sample of about 4,400 households with a total of 19,000 individuals in nine provinces that vary substantially in geography, economic development, public resources, and health indicators. In addition, detailed community data were collected in surveys of food markets, health facilities, family planning officials, and other social services and community leaders.
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CHNS Data Description
The study population is drawn from the nine provinces of Guangxi, Guizhou, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Liaoning, and Shandong.
This sample is diverse with variation found in a wide-ranging set of socioeconomic factors (income, employment, education and modernization) and other related health, nutritional and demographic measures.
A multistage, random cluster process was used to draw the sample surveyed in each of the provinces. Counties in the 9 provinces were stratified by income (low, middle, and high) and a weighted sampling scheme was used to randomly select four counties in each province. In addition, the provincial capital and a lower income city were selected when feasible, except that other large cities rather than provincial capitals had to be selected in two provinces. Villages and townships within the counties and urban and suburban neighborhoods within the cities were selected randomly.
In 1989-1993 there were 190 primary sampling units: 32 urban neighborhoods, 30 suburban neighborhoods, 32 towns (county capital city), and 96 rural villages. Since 2000, the primary sampling units have increased to 216: 36 urban neighborhoods, 36 suburban neighborhoods, 36 towns and 108 villages.
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Sample
CHNS 1989 included 3,795 households. 3,616 households, 3,441 households, 3,875 households, and 4,403 households participated in CHNS 1991, CHNS1993, CHNS 1997 and CHNS 2000, respectively. All individuals in each household were surveyed in 1991, 1993, 1997 and 2000 for all data; however in 1989, health and nutritional data were only collected from preschoolers and adults aged 20-45.
CHNS 1989 surveyed 15,917 individuals. CHNS 1991 only surveyed individuals belonging to the original sample households which resulted in a total of 14,778 individuals. In CHNS 1993, all new households formed from sample households who resided in sample areas were added to this sample, resulting in a total of 13,893 individuals. In CHNS 1997, all newly formed households who resided in sample areas and additional households to replace those no longer participating were added to the sample. New communities were also added to replace communities no longer participating, and Heilongjiang province replaced Liaoning province. A total of 14,426 individuals participated in 1997. In CHNS 2000, newly formed households, replacement households, and replacement communities were again added, and Liaoning province returned to the study. A total of 15,648 individuals participated in 2000.
Household Survey Data Collection
Detailed demographic, economic, time use, labor force participation, asset ownership, and expenditure data were obtained. Income can be approximated from the survey in 3 ways: through responses to direct questions about income, through the summation of net receipts from all reported activities, and through responses to questions about expenditures. Full income from market and non-market activities can be imputed. This detailed estimation of income represents a significant advance in the measurement of income in China. Inclusion of non-monetary government subsidies, such as state-subsidized housing, is an especially important advance. In the health section, details about insurance coverage, availability of medical facilities, curative care and illness information with associated time and money costs, preventive care with a focus on immunizations, and use of family planning and other preventive services were obtained.
Health and Nutrition Survey
All household members in 1991 and subsequent surveys provided individual data on dietary intake, body composition, blood pressure, health history, and health-related behaviors (e.g., smoking, beverage consumption, medication, key chronic diseases). These data include dietary intake for 3 consecutive days as well as detailed physical examinations that include blood pressure (for adults), clinical measures of health, weight, height, and arm and head circumference (and also waist-hip ratios beginning in 1993). The 3 consecutive days during which detailed household food consumption data were collected were randomly allocated from Monday to Sunday and are almost equally balanced across the 7 days of the week for each sampling unit. Household food consumption was determined by examining changes in inventory from the beginning to the end of each day, in combination with a weighing and measurement technique. Chinese balances with a maximum limit of 15 kilograms and a minimum of 20 grams were used. All processed foods (including edible oils and salt) remaining after the last meal before initiation of the survey were weighed and recorded. All purchases, home production, and processed snack foods were recorded. Whenever foods were brought into the household unit, they were weighed and preparation waste (e.g., spoiled rice, discarded cooked meals fed to pets or animals) was estimated when weighing was not possible. At the end of the survey, all remaining foods were again weighed and recorded. The number of household members and visitors were recorded at each meal.
Individual dietary intake for the same three consecutive days was surveyed for all children aged 1 to 6 and all adults aged 20 to 45 in 1989, and for all individuals in later years. This was achieved by asking individuals each day to report all food consumed away from home on a 24-hour recall basis, and the same daily interview was used to collect at-home individual consumption. In a few cases, subjects missed one day due to absence, but over 99 percent of the sample was available for the full three days of data.
The collection of both household and individual dietary intake allowed us to check the quality of data collection by comparing the two. Thus, each individual's average daily dietary intake, calculated from the household survey, was compared with his or her dietary intake based on 24-hour recall data. Where significant discrepancies were found, the household and the individual in question were revisited and asked about their food consumption in order to resolve these discrepancies.
All field workers were trained nutritionists who are otherwise professionally engaged in nutrition work in their own counties and who have participated in other national surveys. Almost all interviewers were graduates of post-secondary schools; many had four-year degrees. In addition, 3 days of specific training in the collection of dietary data were provided for this survey.
The 1991 Food Composition Table (FCT) for China was utilized to calculate nutrient values for the dietary data of 2000 and previous years. This FCT represents a significant advance over the earlier China FCT both for higher quality chemical analyses and for improved techniques of developing average nutrient values for foods whose nutrient value varies over the country in a geographic context. The UNC group has worked with the National Institute of Nutrition and Food Safety to update and improve this FCT. A new version of FCT (2002) was used for 2004 survey and the latest version (2004) was used for 2006 survey.
Child Physical Activity
Two methods of collecting physical activity and inactivity data from respondent children were used, beginning in 1997. The first is based on questionnaires which collect reports of usual time spent in activities common in each of four settings. Activity questionnaires were designed by Barry Popkin and Barbara Ainsworth. Ainsworth was also involved in the design and evaluation of the activity questions for the U.S. Health Interview Surveys (HIS), the MONICA Optional Study of Physical Activity (MOSPA), and more recently the new International Physical Activity questionnaire for WHO. We expanded upon the U.S. HIS questions to include activity and inactivity, including TV viewing and other sedentary activities such as using computers, playing board games, and reading. Activities in and out of school, as well as culture-specific activity at home were included.
The second method involves measurement of motion in a 24-hour period using the Caltrac actometer. A subset of Chinese children provided these data. The Caltrac is a low-cost device that looks like a beeper and is attached to the waist. It registers motion in two dimensions, and gives an estimate of total energy expenditure. The Caltrac was selected because it provides reasonably reliable and valid estimates of total activity, is cost effective, is feasible for use in a variety of field settings, is non-invasive and is well-accepted by children. Questions on sleeping time and the nature of that day for the child are also asked in conjunction with the Caltrac data. However, this was discontinued in 2004.
Adult Physical Activity
A small set of questions about the nature of occupation work was included in 1997 and later surveys to capture some energy expenditure-related dimensions of each adult's work. Included were questions about the physical activity involved in the work. This complements one set of energy expenditure questions that have been asked as part of the nutrition data collection for all adults since 1989.
The Elderly Component
Since 1997 survey, we collect a full series of questions on activities of daily living and instrumental activities of daily living along with a shorter set of cognition questions. Drs. Robert Wallace and Namvar Zohoori developed these in Beijing in collaboration with the Chinese group. Wallace, who is responsible for the health component of the National Health and Retirement Survey in the US, and Zohoori began with a comparable set of questions and adjusted them to fit the Chinese reality. Additional questions have been added on time use for the care of older persons living inside and outside the home, and inter-generational transfers from children to their parents and vice versa. The CHNS obtain data quite similar to that collected by the National Health and Retirement Survey now for many dimensions of elderly behavior. For CHNS93 and all subsequent surveys, we have developed and added questionnaire components on activities of daily living (ADL) and intergenerational transfers from adult children to their older parents and vice versa. With the exception of some adaptation to the Chinese situation, the ADL survey is designed to be comparable with the Health and Retirement Survey and other U.S.-based National Center of Health Statistics surveys. This section was considerably refined based on the state of art at the time of the survey and on the pretests undertaken in China. We collected not only the standard ADL data, but also implemented an independent approach termed the PULSES approach.
The PULSES score is less sensitive for the elderly than for other groups, so it can be used only in an elementary way for checking the predictive ability of the ADL measures. The PULSES score taps a wider dimension than physical functioning, but provides much less detail on each item. Other approaches were used to check the predictive validity of the ADL data. Internal consistency and observer consistency (inter- and intra-observer) studies were undertaken. In addition, CHNS93 enlarged the depth and range of measures of help received by household members as well as parallel measures of help given by household members. We asked about caregiving and help in getting access to scarce or valuable resources. To obtain information about help we added new questions about access to scarce commodities, such as foreign cigarettes or appliances, help in getting special foods needed to treat a variety of illnesses, and help in figuring out how to find the best doctor if someone is ill. For each household member, information about the source of assistance included age, gender, relation to respondent (including living in the household or not, and if not, whether previously resided in the household; and whether the helper was a relative, school classmate, work friend, or neighbor), occupation, and political status (party member, cadre). Similar information was collected about those receiving help from household members. Since a good deal of information about caregiving was already collected, our task was to fill in all the missing pieces so that complete and consistent information was gathered for all household members. The CHNS data are part of a broader initiative to create modules sensitive to questions of aging. Many of the measures mentioned above are part of what is termed inter-generational transfers. The typical and most important categories are the transfer of money between elderly family members (who may or may not be members of the sample household) and the exchange of food, clothing, and child care/elder care.
Body Image and Mass Media Behaviors and Practices
In 2000 and later surveys, body images were created to match Chinese body types. All children aged 6-18 were asked about their desired body type and actual body type using card shuffle techniques. These were developed by Jane Brown and Peggy Bentley with the help of Penny Gordon-Larsen, all UNC faculty working in this area.
In addition, each child was asked a selected set of questions related to the mass media. The mother was asked a series of related questions about mass media and television related to the children. These were included in the Ever-Married Women questionnaire for women with a child aged 6-18.
Ever-Married Women Survey
Information from all ever-married women aged under 52 was collected beginning in 1991. The questions in this section were revised and expanded in 1993. These data include complex marriage and fertility histories and additional information was also collected on family planning, pregnancies, and infant feeding during inter-survey intervals.
Community Survey
The community questionnaire (filled out for each of the primary sampling units) collected information from a knowledgeable respondent on community infrastructure (water, transport, electricity, communications, and so on), services (family planning, health facilities, retail outlets), population, prevailing wages, and related variables.
Food Market Survey
In the first two CHNS surveys, state and free market data were collected. But by 1997, none of our communities had separate state prices so only free market stores and large stores were visited. In all cases prices were collected for a representative basket of commodities.
Health and Family Planning Facility Surveys
In 1989, 1991 and 1993, separate visits were made to obtain in-depth data in each community for every identified health service and family planning provider or facility. Information was collected concerning personnel, sources of funds, services available, prices (asked separately for insured and self-pay patients), and distance to the primary sampling units served by the facility. A separate questionnaire was administered to the local family planning official about family planning policies in the community. These were discontinued in 1997, but selected questions were asked of these same personnel as part of the community questionnaire.
Quality Control Procedures
Extensive changes were made to substantially increase quality control for the 1991 and 1993 rounds of the CHNS (Chinese Health and Nutrition Survey)after some problems were uncovered in the procedures of several provinces as part of the CHNS 1989 activities. Those problems have been corrected and the CHNS 1989 data are now of high quality. The design and implementation of the training of field staff involved in data collection and office staff handling data entry, checking, and cleaning have become an established part of work in China. Extended trips to the U.S. for training and data processing staff have helped with this effort. The Institute felt these visits were so important that they allocated additional scarce foreign exchange funds from their own budget for this training.
The internal controls on quality of measurement are based on collecting measures of selected factors from multiple perspectives and then using these data to refine measurement. One example is dietary fat. Typically, an average amount of fat used on a dish-by-dish basis is used to estimate fat intake. This procedure is also used for other condiments and minor food elements. In this study, the household measures allow us to develop household-specific measurements for factors which truly vary by such an amount as to change energy intake for family members by 12-15%, depending on the use of average or household-specific measures. For income, family composition, and other measures, similar checks are used to provide much more precise refinement of important factors.
Notes
References
- China Health and Nutrition Survey Home
- Popkin, Barry M., Shufa Du, Fengying Zhai, and Bing Zhang. "Cohort Profile: The China Health and Nutrition Survey--monitoring and understanding socio-economic and health change in China, 1989-2011." International journal of epidemiology 39, no. 6 (2009): 1435-1440.
External links
- National Institute of Nutrition and Food Safety
- Chinese Center for Disease Control and Prevention
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