Study Design

What does the study involve?

The CKB involves a detailed baseline survey of study participants with extensive data collection by questionnaire, a range of physical measurements, and collection and storage of blood samples. After the baseline survey, periodic resurveys are to be conducted every 4-5 years, involving each time about 5% of the surviving participants randomly selected from the original cohort. The resurveys will allow the relevance of long-term “usual” levels of risk factors to be assessed by allowing appropriate adjustment for “regression dilution” and other sources of variation. Follow-up of the study participants for cause-specific mortality and morbidity are to be based chiefly on linkage with death and disease registries that are already available in the study regions. Following the recent establishment and consolidation of a nationwide health insurance system both in rural and urban areas, follow-up for any episode involving hospital admission of study participants is also becoming possible.

Who is in the study population?

The study includes over 0.5 million adults aged 30-79 who were recruited from the general population in 10 geographically defined regions of China (5 urban and 5 rural as shown below). These regions were chosen according to local disease patterns, exposure to certain risk factors, population stability, quality of death and disease registries, local commitment and capacity.

What information has been collected at baseline?

At the baseline survey, detailed questionnaire data were collected from each participant, including demographic and socio-economic factors, smoking, alcohol and tea drinking, diet, physical activity, pre-existing diseases and related medication, indoor air pollution now and in the past, reproductive history (women), and sleeping and psychological status. The physical measurements included height, weight, hip and waist circumference, bio-impedance, lung function, carbon monoxide, blood pressure and pulse rate, using standard instruments and protocols and with regular calibrations. In addition, blood spot tests were also done to determine random blood glucose and hepatitis B surface antigen (HBsAg).