The current study investigated the association between SES and MetS in Chinese adults, using the indicators of education, personal monthly income and household monthly income. Since gender differences have been observed in the relationship between socioeconomic position and CVD risk factors, we stratify the analyses by gender. The differences of SES on MetS between men and women were obvious. As for men, after multivariate adjustments, although the odds ratios for MetS increased with higher SES levels, the associations between them were not statistically significant. However, as for women, inverse associations were shown between SES and MetS. To be exact, the ORs decreased with higher SES levels. Lower SES was associated with a high risk for MetS among women but not in men. This was similar to other finding in Korea
] and Portugal
Generally, the prevalence of MetS varied between men and women too. It increased slightly with higher SES for men, while for women it showed an inverse association with SES. And the prevalence of each component of MetS among SES level was also different between men and women. These results were similar to those of Korean National Health and Nutrition Examination
] in terms of overall MetS prevalence, abdominal obesity, high blood pressure and high blood glucose. However, as for high TG and low HDL, they presented obvious differences. For Chinese men, prevalence of high TG and low HDL increased with upgrading SES levels, while in Korea that of high TG and low HDL fluctuated a little among different SES levels. And for Korean women, the prevalence of high TG and low HDL decreased with increasing income, while that of high TG and low HDL showed no significant fluctuation for Chinese women. The reasons for the differences may lie in the fact that during the special economic transition period, Chinese men with higher SES had much more ability and opportunity to consume rich-in-fat foods, which can result in higher TG and lower HDL and Chinese women tend to be more concerned about their fitness. Studies found that income was positively associated with the consumption of snacks and excessive fried food and SES played a vital role in the early stage of eating behavior transition in China
The possible mechanism for the impacts of SES on MetS may through individual’s unhealthy behaviors, such as smoking and drinking. Those with lower SES tended to be more likely to smoke and drink. In addition to that, smoking and drinking are both risk factors for cardiovascular diseases. This would further aggravate the potential risks to develop MetS.
Education has been found to be associated with MetS in many studies
]. The significance that education is a strong predictor of health lies in that education may affect life-style behaviors, psychosocial attitude, accessibility to health services, and economically advantageous surroundings
]. In China, education plays a special role for those with lower SES. It was instrumental to upgrade children belonging to the disadvantageous group to higher SES level, thus increasing their intergenerational income mobility
The importance of income, income inequality, and their associations with health has been discussed in many literatures
]. In our studies, we found significant association between personal monthly income or household monthly income and MetS after the multivariate adjustments for women but not for men. And income inequality was found to be associated with unequal access to health care and morbidity
]. Apart from that, high income inequality increased the probability of health compromising behavior such as smoking and alcohol consumption
], which were both risk factors for MetS.
Additionally, psychosocial stress may be considered as another factor caused by SES in the prevalence of MetS. Lower SES was usually associated with higher levels of cortisol
], which was the risk factor for hypertension
]. These findings might provide an alternative mechanism for the effects of SES on MetS. China is now in the great transition phase for economic and social structure. The polarization of SES, the rising expenditures for foods, education, medical care and housing prices may result in psychological stresses, especially among those with lower SES. This may further aggravate health inequality and diseases associated with MetS.
Apart from that, several factors may contribute to the gender differences in the association between SES and MetS. Women may experience a greater degree of discrimination in all spheres of life (e.g. labor market, pay, household work etc.), and women of low SES might have worse living conditions than low SES men
]. Additionally, women of low SES are exposed to a range of stressors compared to either high SES women or low SES men.
The limitations of our study included the cross-sectional nature and a possible deficiency of causal inferences. In addition, as the information about SES was self-reported, some residents may not provide the precise income. However, the large sample of population represented for Beijing residents, and this enabled us to draw inferences of the association between SES and MetS among community residents in Beijing.