Most previous studies have only assessed the burden of IHD among overall populations without any further stratification regarding temporal or spatial patterns. To the best of our knowledge, this is the first trend analysis focusing on age-, sex-, and province-specific IHD burden over the years 1990 to 2016 including the periods 1990 to 2005 and 2005 to 2016. The results can provide important information for developing IHD prevention and control strategies.
Age and sex disparities
The burden of IHD varied between ages, sexes, and provinces among the Chinese population. Our age-sex-specific analysis demonstrated that the IHD burden among seniors, particularly those aged 70+ years, was markedly higher than those under 49 years old, indicating that age was positively associated with increased risks of IHD. Since this is related to a growing population and rapid aging, it is expected that the middle-aged and elderly individuals should be the foremost concern when managing the IHD burden in China [16,17]. Marked discrepancies in the burden of IHD between sexes were found. YLDs in females were consistently higher than those in males whereas females experienced lower YLLs and DALYs. Behavioral patterns might partly explain the different trends seen in the IHD burden between sexes. In addition to males being more likely to have dreadful habits such as smoking, alcohol consumption, and poor diet which increases their baseline mortality rate of CVD [3], women tended to be active in seeking health care because they were more concerned in general about physical and mental health [10,18]. These findings show that the IHD burden among middle-aged and elderly males should be more widely publicized to manage the overall IHD burden.
Regional trends and disparities
Differences in the IHD burden existed between provinces of China. Most provinces saw a remarkable increase in IHD burden between 1990 and 2016. However, the age-standardised DALY rate experienced a sharp decline in several economically developed provinces, particularly in southeastern coastal areas such as Zhejiang, Hong Kong, and Macao. Socioeconomic status is one possible explanation for the provincial discrepancies, with poorer socioeconomic development being correlated with higher prevalence and death rates of diseases [11,12,19]. Equitable access to essential health services within provinces is a concern in China. The growing IHD burden over the past two decades is particularly obvious in certain remote provinces of less economically developed regions, such as Guizhou and Yunnan, where there is generally lower public awareness of preventive self-care, limited education, weaker health services, and inability to pay for treatment. Furthermore, north-south and west-east disparities in medical resource allocation, environmental conditions, individual metabolism, distribution of risk factors, and lifestyles and behavioral habits also exacerbated the provincial discrepancies [8,11,13,20,21]. The regional disparities were observed across countries worldwide. High-income countries such as South Korea, Denmark, and Israel experienced a considerate reduction in age-standardised DALY rates during 1990–2016, whereas Bangladesh and Uzbekistan in lower-middle income regions had an opposite increasing trend [4]. Tailored strategies of mitigating the IHD burden should be priorities for these countries with limited economic development.
Trends in IHD burden over time
Disparities in the IHD burden over time in China were observed. When comparing the variation in IHD burden in 1990–2005 and 2005–2016, we found that the rapid increase in YLLs had been effectively controlled in the most recent decade by the increase in YLDs. The progressive trend in the increase of YLD can be indicated by substantially increased prevalence of IHD. The China PEACE study showed national rates (per 100,000) of hospital admissions for ST-segment elevation myocardial infarction increased from 3.5 in 2001 to 15.4 in 2011. This rapidly rising incidence increased in its contribution to IHD prevalence [22]. Over the past two decades, improvements in health care services and medical treatments prolonged HALE of the Chinese population [13]. Unfortunately, the improvements contributed to the population growing and ageing, which increased the number of IHD events, especially among the elderly aged >65 years [4, 8, 20]. In addition, most old patients with IHD have comorbid peripheral atherosclerotic disease, but guideline-recommend therapies are unavailable to them [23, 24]. These present considerable challenges for disability control of IHD. While the IHD burden increased from 2005 to 2016, it did so at a relatively slower rate, with no significant differences in YLL in the elderly population during this period. Besides the increased number of older IHD patients, this can be partly explained by the enforcement of policies after 2005. National leadership has launched critical strategies and valuable prevention and control programs related to cardiovascular rehabilitation and tobacco control, along with widely advocating balanced diets and healthy lifestyles to ameliorate growing IHD hazards. In the new epoch seeking to achieve the “Healthy China 2030” [25] and the “13th Five-Year Public Health and Health Care Plan” [26], managing an increasing IHD burden is anticipated to be an uphill battle.
Potential risk factors of IHD
Over the past two decades, demographic shifts, with transitions in economic systems, social structures, environmental factors, life styles, and medical treatments and health-care services have had a widespread and far-reaching impact on potential IHD risk factors [8, 27]. We found wide geographic variation in epidemiology of risk factors among provinces in 2016. Metabolic risks factors including high blood pressure and high LDL cholesterol were the leading contributors of IHD burdens, with diet high in sodium and smoking remaining the main sources of the IHD burden attributable to behavioral risks in China. Exposure to environmental risk factors was associated with economic development, some provinces with weak economies, such as Tibet, had the highest IHD burden due to air pollution from solid fuels, with Beijing and Tianjin, rich in resources, experiencing the highest IHD burdens attributable to ambient particulate matter. Consistent with previous studies, our findings suggest the need to take tailored steps to mitigate exposure to risk factors such as physical inactivity, hypertension, high LDL-cholesterol levels, diabetes, and the low rates of education regarding the tertiary prevention of IHD [7, 28-33].
Study strengths and implications for policies
Several studies paying attention to the increased burden of IHD in China have been carried out. Most previous studies mainly conducted at the local level with a limited time frame and failed to provide an overall temporal and geographical trend analysis considering both demographic characteristics and provincial disparities [9-11,16,17, 34]. Our study provided comprehensive estimates of the IHD burden among Chinese and subgroup populations according to age, sex, and regions, with in-depth analyse of regional differences in risk factors at the provincial level. Through this we have uncovered some potentially valuable insights which can influence policy decisions. Firstly, we call for priorities aimed at improving the health level of general populations, particularly among middle-aged and elderly males engaging in high-risk behaviors. Better guidance in implementing targeted health policies at the provincial level needs to be emphasized, while also allowing for more accessible approaches based on different economic levels across provinces of China. Health authorities should pay more attention to the issue of “health inequality” and ensure that everyone is available to psychological well-being, regardless of their socio-economic status, gender, ethnicity, and residency. Our findings also uncover valuable insights for informing local governments of tailored strategies and programmes to reduce the prevalence of IHD risk factors.
While it improves on previous studies, this study has some limitations. Although our analysis of IHD burden was conducted at national and provincial levels, the disease burden at the county level and urban-rural discrepancies were not examined. The gaps between assessments at national/provincial levels and district levels were somewhat limited to measure a shift in the local disease burden and effectively and specifically influence public policies, which underscores the need for future district level studies [35]. Although the GBD 2016 study had updated the epidemiological data and analytic methodology, changes in diagnostic technology over time might cause inevitable measurement errors in the acquisition of data [2-5]. With regard to the estimation of YLDs, the calculation of disability weighting is based on multinational results, and precise data on non-fatal outcomes of IHD are insufficient. These may cause uncertainty for China [2].