Socioeconomic status (SES) refers to a person's place in a class system and includes factors like education, income, occupation, wealth, and place of residence. SES widens health gradients between groups by helping individuals gain health advantages [1, 2]. Many previous studies have reported the presence of SES-health gradients. According to a meta-analysis, those with the lowest SES in terms of income, occupation, and education had a higher prevalence of hypertension than those with the greatest SES[3]. In the context of an aging society, linked to social stratification, individual health inequalities may tend to expand with age, which is also known as the cumulative disadvantage of health disparity.
In 2019, cardiovascular diseases (CVDs) in rural and urban areas in China accounted for 46.74% and 44.26% of the causes of mortality, respectively[4]. CVDs have become the leading cause of death in both China and the world, and hypertension is a major risk factor for CVDs, causing a serious risk to human health[5]. According to a 2017 survey, the prevalence of hypertension among people over the age of 18 in the Tibet autonomous area was 24.7%[6]. With socioeconomic development, population aging, and the acceleration of urbanization, the prevalence of hypertension is on the rise, and it has become a major public health problem [7].
SES and obesity are known to be predictors of hypertension, and there is substantial evidence that SES is associated with traditional risk factors for hypertension (health knowledge, health behaviors and lifestyle, working conditions, medical care, income, socio-psychological resources)[8–10]. Research on obesity has shown that body fat distribution, especially the accumulation of abdominal fat, has a high correlation with CVDs, which is of great value in predicting the risk of CVDs [11]. There is now a debate on a global scale on the usefulness of several obesity markers in foretelling the onset of hypertension. Part of study using a single obesity indicator to predict hypertension may weaken the convincing power. In addition, the existing related studies have the following problems. First, there have been many reviews on the relationship and pathway between SES, obesity and hypertension. However, little study has been done on how SES and obesity interact with one another to cause hypertension. Second, earlier research tended to reflect the whole level of a person's socioeconomic position with a single measure [12], so it is necessary to establish a comprehensive SES index to comprehensively reflect its effect on obesity and hypertension. Third, Tibet is located in the southwest of the Tibet Plateau, with an average altitude of over 4,000 meters[13]. The permanent population of Tibetans accounts for 85.74%. With the development of society and economy, ethnic minorities in plateau areas are more likely to obtain high-oil, high-sugar, and high-sodium foods [14]. At the same time, the lack of healthy lifestyles and health interventions, the harsh natural environment with high cold and low oxygen, and complex ethnic cultural traditions and customs have created unique, complex, and severe health problems[15, 16] and behavioral risk factors[17].According to a Chinese research, people of the Tibet autonomous region had lower overall health than those in other Chinese provinces[18]. Therefore, the relationship between SES, obesity, and hypertension of Tibetans warrants further explore.
In summary, we use data from the China Multi-Ethnic Cohort Study (CMEC), which was carried out in five provinces in southwest China from May 2018 to September 2019. We selected Tibetan adults as study subjects, and used multiple obesity indicators (BMI, WC, and WHtR) to assess the complex relations of obesity and SES with hypertension.