Voir page 1303 le resume en francais. En la pagina 1303 figura un resumen en espanol.
Although cardiovascular disease (CVD) has been falling as a major cause of death in developed countries, it is on the increase in developing countries (1-3). It has been shown consistently that socioeconomic status (SES) is inversely associated with cardiovascular morbidity and mortality (4-8). In developed countries, the declining trend in CVD has been more pronounced among individuals in higher socioeconomic groups, and the differences in the occurrence of CVD between higher and the lower socioeconomic groups is widening (8-12). Regardless of which measure of SES is used, there is abundant evidence for the existence of an inverse relationship between SES and cardiovascular risk factors in developed countries, with only few exceptions (12). Preventive activities contributing to the decline in CVD might have had a greater impact on individuals' health in higher socioeconomic groups and resulted in widening cardiovascular disparities in industrialized societies (13, 14).
China is the largest developing country in the world and CVD has become the major cause of death especially in urban areas (15) such as Tianjin, the third largest city in the country. Mortality from heart diseases and stroke accounted for 51-56% of all deaths in the mid-1980s in the city. In 1984, a community-based intervention programme, the Tianjin Project, aimed at the prevention and control of CVD through lifestyle and risk factor changes, was initiated in the city (16). This was the first attempt to identify ways to prevent and control chronic diseases in China (17). Few assessments have been carried out to examine the association between SES and cardiovascular risk factors in China. For example, Tian et al. reported that blood pressure was inversely associated with level of education in an urban population (18); and middle-aged male workers with lower educational attainment or heavier labour intensity had increased levels of cardiovascular risk factors in a study sample from seven steel and metal plants (19). Previous reports from China quantifying the effects of different dimensions of SES on cardiovascular risk factors are sparse. A population survey carried out in Tianjin provided an opportunity for us to conduct a cross-sectional assessment of SES and cardiovascular risk factors. The aim of this study was to investigate the association between education, occupation, income, and marital status, and three cardiovascular risk factors -- blood pressure, body mass index, and cigarette smoking.
Materials and methods
In 1996, a cross-sectional population survey was conducted in the city of Tianjin. This survey serves as the baseline for a 5-year intervention programme that was funded by the World Bank. The alms of this programme are to decrease levels of behavioural risk factors for noncommunicable chronic diseases, injuries, and sexually transmitted diseases through legislative and environmental changes using the population approach intervention strategy (20). The programme was started in 1996 and will be completed in 2000.
The city of Tianjin has a population of 9.5 million, of whom 4 million people live in the six urban districts. The sample of this study was drawn using a two-stage sampling. First, 14 communities comprising 400 000 inhabitants were drawn randomly from these six urban districts. The sample included at least two communities from each district. In the second stage, 4000 individuals aged 15-69 years were drawn randomly from the local population registers in the sampled communities. The sample was stratified by sex and into five 10-year age groups (oldest age group, 55-69 years). The subsample of each sampled community was almost the same size. The overall response rate was 100%. The number of persons in the five age strata were as follows: age range 1524 years: 793 (19.8%; 399 men and 394 women); age range 25-34 years: 815 (20. …