Cohort Profile: The Henan Rural Cohort: a prospective study of chronic non-communicable diseases

Abstract

With the rapid development of social mobility, change of lifestyle and environment and ageing of the population, chronic non-communicable diseases (NCDs) such as stroke, coronary heart disease, cancer, diabetes mellitus, hypertension, dyslipidaemia, obesity and chronic lung disease, have become leading causes of death globally.1 Although the steady increase in the prevalence of NCDs has slowed in some high-income countries, the global burden of NCDs is still rising due to its increasing prevalence in low- and middle-income countries, where 80% of all global NCD-related deaths occur.1 As a populous and large agricultural country, China is contributing the largest number of NCDs patients and deaths due to ageing, lifestyle changes and psychosocial stress.2–4 Although great efforts have been made to control NCDs in China, the prevalence of NCDs still continues to increase, especially in rural areas with limited resources.5–8 The latest report showed that the prevalence of NCDs had climbed from 15.3% in 2003 to 29.5% in 2013 in rural areas, and the increase of incidence rates in rural areas exceeds that of those in cities (the corresponding rates were 27.7% and 36.7%, respectively).9 In addition, rural NCD patients are facing the risks of disability and life-threatening conditions that result from complications of NCDs because of lack of medical service resources and coverage by health care systems.8,9 Therefore, it is urgent to understand the potential risk factors contributing to rural China’s current epidemic of NCDs, and then to adopt effective intervention measures to improve the prevention of NCDs and reduce the disease burden in Chinese rural residents. Inherited factors, multiple environmental exposures and behavioural factors likely contribute to the growing burden of NCDs in the Chinese rural population. However, the relative contribution of these various risk factors has not yet been clearly determined. Although some genome-wide association studies (GWAS) have identified a large number of common gene variants for some chronic diseases,10–13 the conclusions are not entirely appropriate for the Chinese people, especially for Chinese rural populations considering the diversities in ethnicity, economic level, education, dietary factors and behavioural/lifestyle factors. In addition to inherited and behavioural factors, unique environmental exposures, such as pesticides, metal elements and air pollution, are also thought to contribute to NCDs’ development and mortality.14–20 To address the urgent need for data on NCDs prevalence, risk factors and associated conditions in resource-constrained settings, the Henan Rural Cohort study was launched in Henan from July 2015 to September 2017 based on a standardized survey approach and stringent quality control measures.21 Henan province is located in central China, with a permanent resident population of approximate 94 million in 2010.22 It is an important province in agricultural production, with a rural population accounting for 79% of the total population. However, definitive data on prevalence of NCDs and their risk factors remain limited in Chinese rural areas. The purposes of the Henan Rural Cohort study were to: (1) determine the prevalence of stroke, coronary heart disease, cancer, diabetes mellitus, hypertension, dyslipidaemia, obesity, osteoporosis, mental disorders and other common NCDs in a rural Chinese adult population; (2) estimate the disease burden and complications of NCDs indicated above; (3) describe the temporal dynamics of NCD prevalence and their risk factors; (4) assess the effects of environmental exposures, lifestyle and genetics on NCDs; (5) develop and evaluate morbidity and mortality risk assessment tools for NCDs; (6) explore the underlying causes of NCDs and then aid in the development of strategies to prevent and control the diseases in resource-constrained settings. The Henan Rural Cohort was established in five rural regions (Suiping county, Yuzhou county, Xinxiang county, Tongxu county and Yima county) of Henan province in China, and the baseline survey was carried out between July 2015 and September 2017 (Figure 1). A multistage, stratified cluster sampling method was used to obtain samples in the general population. The target population was adults aged 18–79 years who were permanent residents and available for completing follow-up studies of mortality and morbidity. An individual was excluded if they had a severe physical or mental disease that made them unable to answer the questionnaire or if they had a severe medical condition that made them unable to report to the survey location. In the first stage, five rural counties were selected from different geographical regions (south, central, north, east, and west) in Henan province through simple cluster sampling. In the second stage, one to three rural communities (referred to as ‘townships’) in each county were selected by the local Centre for Disease Control and Prevention i