The rapid socioeconomic progress in China has had a great impact on the lifestyle of the population. With the acceleration in urbanisation, industrialisation, ageing and lifestyle changes, the prevalence of cardiovascular disease (CVD) in China has dramatically increased and will remain on an upward trend in the next decades.1 According to a 2012 report on CVDs in China, an estimated 290 million individuals suffered from CVD and 3.5 million died of CVD every year, which accounted for 41% of all-cause deaths.2 CVD has become the top killer for the Chinese population.2 The increasing disease burden of CVD has become a major public health issue. The ongoing deterioration in cardiovascular risk factors (CRFs) appears to be the major cause of inducing the CVD epidemic in China.1

It is well known that cigarette smoking, overweight or obesity, hypertension, diabetes and dyslipidaemia are five major modifiable CRFs that can be altered or eliminated through proper management.3–11 A number of studies have indicated that the prevalence of CRFs has increased in recent decades in China.3–7 9–11 Furthermore, the clustering of these risk factors in the same individual will significantly increase risk of CVD events compared with a single risk factor.4 6 9–12 A complete assessment of the distribution and aggregate of well-established CRFs depicts the risk of developing CVD and is useful in formulating effective prevention strategies.

CVD is the leading cause of mortality in Nanjing, accounting for approximately 43% of total deaths in 2012.13 Although there have been similar studies previously in foreign countries,8 14–18 there has been no large-scale study with an adequate sample size to evaluate the prevalence and clustering of CVD risk factors in Nanjing. In the present study, we performed a community-based survey to estimate the up-to-date prevalence and clustering of CVD risk factors, and investigate the association between relevant characteristics and CVD risk factor clustering among a large representative sample of the Nanjing adult population from eastern China.

As shown in table 1, in a total of 39 840 participants (18–86 years, mean age 47.9±16.2 years), 17 964 (45.1%) were men and 21 876 (54.9%) were women. More than four-fifths (84.6%) of the residents were married, nearly half (47.9%) were manual labourers, 50.4% had an education level of junior or senior high school, and 42.5% had a middle level of annual family income. Nearly 60% (59.1%) of adults were from rural areas. The proportions of participants with sufficient PA and healthy dietary habits were 36.3% and 26.3%, respectively. Compared with women, men had a higher level of BMI, SBP, DBP, TC and TG (all p<0.01).

The weighed prevalence of hypertension, diabetes, dyslipidaemia, overweight or obesity, and current smoking was 23.9%, 6.2%, 28.9%, 35.6% and 24.5%, respectively. The weighted prevalence of hypertension, dyslipidaemia, overweight or obesity, and current smoking was higher in men than in women (all p<0.001), except for diabetes. The weighed prevalence of these risk factors increased significantly with age for the general population regardless of gender (all p<0.001). The proportion of CRFs tended to be higher among participants who lost a life partner (all p<0.001). The prevalence of CRFs decreased with the increasing level of education and family income (all p<0.001). The prevalence of hypertension, diabetes and dyslipidaemia was the highest in unemployed and retired people (all p<0.001). Moreover, the prevalence of hypertension, diabetes and dyslipidaemia was greater in rural areas than in urban areas (tables 2 and3).

Overall, 34.7, 30.1%, 20.8%, 10.6%, 3.3% and 0.5% of Nanjing adults had zero, one, two, three, four and five risk factors, respectively. In total 65.3% and 35.2% of the population had at least one or at least two CVD risk factors. There were 23.4% and 46.8% of men and women having no risk factor, respectively. In contrast, 31.4% and 45.2% of men, and 28.7% and 24.6% of women had one and at least two of these risk factors, respectively. The weighted prevalence of at least two risk factors was higher in men than in women (p <0.001). The prevalence of  at least two CVD risk factors increased with age for the overall population of both genders (all p <0.001). Regardless of men and women, there was a decreasing trend towards CVD risk factor clustering with increasing levels of education and yearly family income (all p<0.001). In addition, the clustering of CVD risk factors was higher among unemployed and retired people, and those with insufficient PA or unhealthy diets compared with their counterparts, respectively (all p <0.001) (tables 4 andTable 5).

The combinations of dyslipidaemia/overweight or obesity, hypertension/overweight or obesity, and current smoking/overweight or obesity were the three most common of all two risk factors clustering; the proportions were 22.4%, 20.5% and 18.2%, respectively. Moreover, the clustering of hypertension/dyslipidaemia/overweight or obesity, and the clustering of hypertension/dyslipidaemia/overweight or obesity/current smoking were the most frequent among combinations of three or four risk factors; their proportions were 32.6% and 58.0%, respectively.

As shown in table 6, the multinomial logistic regression analysis showed that men, the elderly, rural residents, participants who had lower levels of SES or those who had lost a life partner, and those with insufficient PA or unhealthy diets were more likely to have one or at least two CVD risk factors compared with women, the young, urban residents, participants who had higher levels of SES or were single, and those with sufficient PA or healthy diets, respectively.

With economic development and urbanisation changes in lifestyle behaviours, China has experienced a rapid increase in the prevalence of CVD and its related risk factors. To our knowledge, the present study is the first study to estimate the up-to-date prevalence and clustering of major CVD risk factors among a large representative sample of the Nanjing adult population from eastern China.

In this community-based cross-sectional study, we found that the prevalence of overweight or obesity, dyslipidaemia, and smoking were ranked as the top three CVD risk factors in the general population. The most prominent risk factor among men and women was smoking and overweight or obesity, respectively. The prevalence of overweight or obesity in our study was much lower than that observed in the nationwide population34 and some other regional studies,4 35 but our findings were close to a recent Tibetan population study.3 Moreover, the prevalence of dyslipidaemia was significantly lower than the national level in a recent cross-sectional study.36 The present study showed that the prevalence of smoking was lower than that in the China Global Adults Tobacco Survey of 2010.37 Additionally, the prevalence of these CRFs among Nanjing adults was similar to that in other developed Asian countries,17 18 but was lower than in developing countries.14 15

Emerging evidence revealed that the synergistic effect of CVD risk factor clustering was associated with a higher risk of developing preclinical CVD and CVD events.38 39 Previous studies confirmed that the clustering of CRFs had more harmful cardiovascular effects than a single risk factor.4 6 9–12 Risk for CVD and all-cause mortality increased substantially with each additional risk factor. Data from the First National Health and Nutrition Examination Surveys Epidemiologic Follow-up Study showed that more than 50% of the incidence of coronary heart disease, stroke and all-cause mortality was attributable to having one risk factor, while the attributable risk was more than 70% for participants with three risk factors.40 Therefore, assessment of CVD risk factor clustering is crucial to identify a high-risk population.

In the present study, 34.7%, 30.1% and 35.2% of participants had zero, one, and two or more major CRFs, respectively, among residents aged ≥18 years. A higher level of clustering of the five CVD risk factors was found in the general Chinese population over the last decade. In a nationally representative sample of 46 239 adults aged ≥20 years from the 2007–2008 China National Diabetes and Metabolic Disorders Study, the proportions of respondents with zero, one and at least two CVD risk factors were 13.5%, 31.2% and 55.3%, respectively.41 In another national study of 23 010 Chinese adults ≥18 years from the 2007–2011 Chinese Physiological Constant and Health Condition, 29.7%, 30.0% and 40.3% of participants had zero, one and at least two CRFs, respectively.6 Compared with these two national studies mentioned above,6 41 Nanjing residents had a lower proportion of two or more CVD risk factors and a higher proportion of no risk factor.

Our results were similar to other related studies in China.12 42 Among 46 683 Chinese from the 2009–2010 China National Survey of chronic kidney disease, the prevalence of having at least two risk factors was 36.2%.12 Overall, 30.9%, 36.4% and 32.7% of participants had zero, one and at least two CRFs, respectively, in 37 141 adults ≥18 years in a healthy screening population of Changchun in the Jilin Province of North-East China.42 Unfortunately, since these two studies did not include current smoking as a CVD risk factor, the clustering of CVD risk factors may underestimate the actual value. We also found that the clustering of dyslipidaemia/overweight or obesity, hypertension/dyslipidaemia/overweight or obesity, and hypertension/dyslipidaemia/overweight or obesity/current smoking were the most common among combinations of two, three and four risk factors, respectively.

Clustering of CVD risk factors has also been observed in other Asian countries that have experienced rapid socioeconomic growth like China.15–18 Clustering of three or more CVD risk factors was presented in 22.7% of the men and 21.7% of the women in South Korea.17 In Malaysia, 33% of the national population had two or more risk factors.18 The proportions of adults with two, three and at least four risk factors were 23.1%, 15.5% and 8.4%, respectively, in South-Western Nigeria.16 A total of 78.6% subjects had two or more risk factors in different parts of India.15

Our study showed that men and the elderly were more likely to have two or more CVD risk factors compared with women and the young, in accordance with other previous studies.3 4 6 7 10 11 The gender disparities may be due to the fact that Chinese men assume more responsibility in society, tend to smoke more cigarettes and be more susceptible to psychological stress than women. In contrast, Chinese women tend to have more awareness of body weight especially in their young and middle years, which could translate into favourable cardiovascular risk profiles. However, the sex discrepancy in CVD risk factor clustering does not exist in other economically developed countries. In both South Korea and Malaysia,17 18 the prevalence of obesity in women was significantly higher than in men, and clustering of CRFs was more common in women. The result that the clustering of CVD risk factors increased progressively with age may attribute to the increasing prevalence of each risk factor with age. Our data showed that the clustering of CVD risk factors was more common in rural areas than in urban areas, inconsistent with other previous studies.5 9 Urban-rural differences may be explained by the rapid urbanisation of rural areas, and the improvement of the healthcare system and health conditions in urban areas in China.

Our study demonstrated that the level of SES was negatively associated with CVD risk factor clustering. As the level of SES increased, the number of CVD risk factors decreased, which was consistent with other reports.3 4 8 12 Socioeconomic inequalities may have unequal access to the knowledge of chronic disease control and prevention, healthcare services and medical resources. Socioeconomic disparities may eventually lead to health behaviours inequality with various SES levels.

The present study also showed that insufficient PA and unhealthy diets were positively associated with the clustering of CVD risk factors. Unhealthy lifestyle behaviours were still prevalent in Nanjing, in line with other domestic studies.43 44 Unhealthy lifestyle behaviours may play an important role in the process of atherosclerosis by leading to physiological changes.45 46 Lifestyle modification was the most important strategy in preventing CVD risk factors under the supervision of the government. In 2012, the blueprint for non-communicable diseases (NCDs) prevention and control in China (2012–2015) issued by 15 multispectral ministries including the Ministry of National Health and Family Planning was implemented, which promoted a  nationwide healthy lifestyle initiative. A new operating paradigm for NCD prevention and control has been formed, featuring the government’s leading role, multisectoral coordination, social mobilisation and extensive participation.

In the Health Nanjing 2030 programme, the Nanjing Municipal Health and Family Planning Commission has stated strong support for four main NCDs (CVD, diabetes, cancer and chronic respiratory disease) prevention and control, and is planning a corresponding regional health policy. First, only 18 cities have legislated to ban smoking in public areas at present, not including Nanjing city. The implementation of the smoking ban in public places will be promoted, and complete smoke-free indoor public places is gradually being accomplished in Nanjing. By 2020, all of the schools, party and government organisations, enterprises and institutions, medical and health agencies are required to be smoke-free. The overall smoking rate over 15 years of age will drop to 20.0% in 2030. Second, the physical fitness awareness of all residents in Nanjing will be further enhanced; the physical quality and health level of people will be continuously improved by 2030. All communities or villages will provide practical basic public sports and fitness facilities, and an urban-rural ‘15 min fitness circle’ shall be completely formed. Meanwhile, it is required to make efforts to provide free or low-cost sports fields and facilities, and public sports facilities and sports grounds of schools meeting conditions shall be 100% open to the public. Third, healthy nutrient products should be available to the public, especially green, organic, pollution-free and protein-rich foods. Nutrition and health knowledge should be spread and popularised. The use of salt, oil and sugar in processed foods should be controlled and reduced. The daily intake of salt in 2030 will be reduced relatively by 20% from the 2011 level in Nanjing.47 Final, more behaviour modification efforts are required to achieve CVD risk factor reduction. The effectively primary, secondary and tertiary prevention of CVD risk factors can substantially decrease the risk of developing CVD.

An advantage of the present study was that the results were based on a community-based study with a large representative sample of residents in Nanjing, which ensured sufficient power for calculation of regional estimates. Additionally, the high-quality study design and implementation with a high response rate, application of standard protocols and instruments, data collection by trained interviewers, and vigorous quality control throughout the survey period, in all the above ensured the validity of our self-reported data.

Our study also had several limitations. First, the cross-sectional design cannot determine the causality or temporal relationship between the clustering of CVD risk factors and CVD. However, previous studies demonstrated that these risk factors were more likely to develop CVD events in Chinese adults.48 Second, the oral glucose tolerance test was not performed in the present study, which could underestimate the prevalence of diabetes. Third, the information on current smoking status was based on self-report, which could be subject to reporting bias. Moreover, those who smoked one cigarette per day irregularly or less than 18 packs in total each year were not included in current smokers. Therefore, the prevalence of current smoking may be under-reported. Final, the mean of the second and third BP measurements in single-visit BP measurements was calculated for analyses, which could overestimate the prevalence of hypertension.

In summary, this cross-sectional study provides a regional prevalence and clustering of CVD risk factors in Nanjing, and fills the information gap in this region. Our analyses indicate that men, elderly people, rural residents and participants with lower levels of SES or unhealthy lifestyle behaviours are susceptible to CVD modifiable risk factor clustering, known as high-risk groups. It is important to focus on the prevention of CVD risk factors among the overall population and especially the vulnerable population in China. Consequently, the Nanjing government has developed effective public health policies at the regional level, such as avoidance or cessation of smoking in public areas, popularising scientific knowledge, enhancing the public’s health awareness, organising health promotion programmes, producing healthy nutrient foods, providing free or low-cost public sports facilities and fitness facilities, strengthening major chronic diseases prevention and control, and improving the medical service system and basic public health service, to reduce the prevalence and clustering of CVD risk factors.