The results of the present study indicated that 90.4% of Kazakh, 91.9% of Uygur, 90.4% of Mongolian, 85.1% of Han individuals had at least one of the following CRFs: hypertension; dyslipidemia; DM; were current smokers; and were overweight. Clustering of ≥2 or ≥3 of these CRFs was noted in 65.2% or 32.1% of Kazakh, 64.8% or 33.0% of Uygur, 66.9% or 36.5% of Mongolian, and 62.0% or 28.3% of Han subjects, respectively. Compared with the Han population, the adjusted ORs of ≥1, ≥2, and ≥3 CVD risk factors for Kazakh, Uygur and Mongolian subjects were higher.
Several studies have noted the striking differences across ethnic groups in the prevalence of CRFs and CVD in other parts of the world
]. A key finding from the current study was that the Chinese Kazakh, Uygur, Mongolian and Han populations had distinct CRF clustering. The age-standardized prevalence of the clustering of CRFs was higher in Uygur, Kazakh and Mongolian populations than in the Han population even though the current smoking status was higher in the Han population. The significantly higher prevalence of ≥1, ≥2, and ≥3 CRFs in Uygur, Kazakh and Mongolian populations compared with the Han population may be due to the striking differences across ethnic groups with regard to the prevalence of hypertension, DM, dyslipidemia, obesity and being overweight. After a careful re-analysis of the characteristics of participants from the populations in the present study, it appears that the Kazakh, Uygur and Mongolian populations had a higher prevalence of hypertension (53.9%, 40.0%, and 55.9%, respectively), being overweight (66.0%, 70.0%, and 67.5%, respectively) and dyslipidemia (68.6%, 72.1%, and 63.1%, respectively) compared with the Han population (hypertension, 33.0%; being overweight, 52.5%; dyslipidemia, 49.0%). The striking differences across ethnic groups with regard to the prevalence of CRFs suggests the need for the development of ethnic-specific and cost-effective CVD prevention programs and health services to reduce the prevalence of CRFs as well as morbidity and mortality from CVD in the Chinese Uygur, Kazakh, Mongolian and Han populations in the Xinjiang in China.
With regard to the striking differences across ethnic groups in the prevalence of hypertension, DM, dyslipidemia, obesity and being overweight, the mechanisms underlying this phenomenon are not clear. It is believed that different environmental exposures among Chinese Uygur, Kazakh, Mongolian, and Han ethnic groups may play an important part. Besides the Han population, the inhabited area of Chinese Uygur, Kazakh and Mongolian populations is relatively isolated and fixed. Most Kazakhs and Mongolians live as herders and reside in the villages and forests north of Xinjiang, which are cold and semi-arid, whereas most Uygurs live as farmers in the plains south of Xinjiang, which are hot and arid. Moreover, Chinese Uygur, Kazakh and Mongolian share similar dietary habits. These are characterized by drinking strong wine, eating more animal fat, with a higher salt intake (>20 g per day) and consuming less grain, fresh vegetables, beans, bean products, and unsaturated fatty acids
]. In addition to different environmental exposures among Chinese Uygur, Kazakh, Mongolian, and Han ethnic groups, differences in genetic backgrounds and gene–environment interactions could also be important factors underlying the different prevalence of hypertension
]. A further study between these CRFs and ethnic-specific genetic susceptibility is needed to clarify this observation.
There is emerging evidence that the synergistic effect of CRFs clustering is associated with CVD and a higher prevalence of cardiovascular events
]. Recent studies have confirmed that the clustering of these risk factors has more harmful cardiovascular effects than that predicted by a single risk factor
]. In those studies, CVD incidence and all-cause mortality increased substantially in the presence of progressively more risk factors. For example, using data from the First NHANES Epidemiologic Follow-up Study, the age-, race-, sex-, and education-adjusted relative risks of coronary heart disease during 21 years of follow-up in adults with 1, 2, 3, 4 or 5 CRFs (hypertension, high cholesterol, DM, being overweight, and current smoking) compared with their counterparts with none of these CRFs were 1.6, 2.2, 3.1, and 5.0, respectively
]. In the present study, the much higher age-standardized prevalence of having clustering of ≥1, ≥2, and ≥3 CRFs (hypertension, dyslipidemia, DM, current smoking, and being overweight) were detected in Chinese Kazakh (90.4%, 65.2% and 32.1%, respectively), Chinese Uygur (91.9%, 64.8% and 33.0%, respectively) and Mongolian (90.4%, 66.9% and 36.5%, respectively) subjects, which suggests that those people were exposed to a higher risk of CVD. Clearly, more effective prevention efforts targeting CRFs are needed in these populations. Also, future public health interventions need to take into account the special needs of people living in Xinjiang. Another important finding was that the age-standardized prevalence of clustering of ≥1, ≥2, and ≥3 CRFs in Chinese Kazakh, Uygur, Mongolian and Han populations was higher than subjects in the InterASIA Study (China) and close to their counterparts in the USA. This finding indicated that the clustering of CRFs is increasing at a rapid speed in China during recent years with the increasing prevalence of hypertension, DM, dyslipidemia, smoking, obesity and being overweight. Also, effective population-based interventions such as smoking cessation, improved diet (reduction of salt and fat), and increased physical activity can safely and effectively lower the risk of CVD
]. A multifaceted and targeted approach aimed at prevention, detection, and treatment of hypertension, dyslipidemia, DM, and obesity could substantially reduce the prevalence of each CRF, CRF clustering, as well as morbidity and mortality from CVD in Xinjiang.
The strengths of the present study include the fact that its results are based on findings in a large, representative sample of adult Chinese Kazakh, Uygur, Mongolian and Han populations. In addition, a high response rate was achieved, standard protocols and instruments were used, the training and certification requirements for data collection were strict, and a vigorous quality-assurance program ensured that high-quality data were collected. Co-existence of different ethnic populations is common in many countries. Their genetic background, lifestyle, and environmental exposures have extensive impacts on risk factors and diseases. Elucidating the effects of these factors and adopting preventive measures will help to reduce the occurrence of diseases and improve health.
A limitation of the present study was reliance upon estimates derived from a cross-sectional study. Cross-sectional studies do not allow for quantification of the importance of CRF clustering in the prevalence of CVD. Nevertheless, a further prospective study could be considered among this population in the future. Moreover, physical inactivity was excluded as a CRF in the present analyses because it is causally involved in the development of all the CRFs investigated except for cigarette smoking. Inclusion of physical inactivity as a risk factor would have artificially increased the prevalence of CRF clustering. Finally, we recognize that diversity is present within each of the four ethnic groups studied, and that the ethnic differences presented in this study are the results of complex interactions between genetics, lifestyle, socio-economic status, provision of healthcare, and reporting. Further examination of these interactions is necessary.