Most previous studies have only assessed the disease burden of IHD across overall populations without any further stratification regarding age, sex, or provincial and temporal or spatial patterns. To the best of our knowledge, this study is the first overall analysis focusing on the temporal and spatial trends of age-, sex-, and province-specific IHD burden based on representative data from the GBD 2016 study over the periods of 1990 to 2016, 1990 to 2005, and 2005 to 2016, in Chinese and subgroup populations. Its results should provide important information for developing IHD prevention and control strategies.
Age and sex disparities
The disease burden of IHD varied between ages and sexes among the Chinese population. The 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 middle-aged and elderly individuals should be the foremost concern when assessing future IHD burden in China [16,17]. This suggests that a major health education initiative, rallying community members to extend care for seniors and tertiary intervention providing timely diagnosis, treatment, and rehabilitation for geriatrics suffering from IHD should be encouraged by health authorities at the grassroots level.
Marked discrepancies in the disease burden from 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 are more 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
Marked regional disparities in the IHD burden were observed in the spatial trend studies across various provinces of China. Most of the provinces saw a remarkable increase in IHD burden between 1990 and 2016. The age-standardized DALY rate experienced a sharp decline in several economically developed provinces, particularly in southeastern coastal areas such as Zhejiang, Hong Kong, and Macao, which may be due to the growing population and extended life expectancy in these economically advantaged areas. Socioeconomic status is one possible explanation for the provincial discrepancies with poorer socioeconomic development correlated with a higher prevalence and death rate of diseases [11,12,19]. Equitable access to essential health services within provinces is a concern in China and the significantly 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, all of which exacerbates the situation of unmet needs. Furthermore, north-south, and west-east disparities in medical resource allocation, regional environmental conditions, individual metabolism, distribution of risk factors, lifestyles and behavioral habits may also be factors in the discrepancies seen in locational variation of IHD burden [8,11,13,20,21].
Trends in IHD burden over time
Disparities in the IHD burden over various time periods in China were observed. When comparing the variation in IHD burden in 1990-2005 and 2005-2016, we found that the rapid increase in IHD-related premature death had been effectively controlled in the most recent decade by the increase in IHD-related disability, which can be correlated with the improvement in health care services, prolonged HALE, extensive health insurance coverage, and timely medical treatments over the same time period [8,20]. While the IHD burden increased from 2005 to 2016, it did so at a relatively slower rate. National leadership has launched critical strategies and valuable prevention and control programs related to cardiovascular rehabilitation and tobacco control, along with widely advocating a balanced diet and healthy lifestyles to ameliorate growing IHD hazards. In the new epoch seeking to achieve the “Healthy China 2030” [22], the “13th Five-Year Public Health and Health Care Plan” [23], and the “Sustainable Development Goals” (SDGs), managing an increasing IHD burden is anticipated to be an uphill battle.
Potential risk factors of IHD
Over the past 20 years, quality of life, life expectancy, health life expectancy, and income conditions of general populations have dramatically improved, which leads to an ageing population [4]. The rises seen in IHD DALYs and the age-standardized DALYs from 1990 to 2016 were inconsistent. This indicates that in addition to critical drivers such as the rapid growth and ageing of the Chinese population, they may also be closely related to the epidemiology of four behavioral NCD risk factors, i.e., tobacco use, alcohol consumption, unhealthy diet, and physical inactivity [11,16,17]. Demographic shifts, with transitions in economic systems, social structures, environmental factors, life styles, and medical treatments and health-care services have gradually had a widespread and far-reaching impact on potential IHD risk factors [8,24]. Previous studies have attempted to assess the disease burden attributable to risk factors and their findings highlighted the changes in major controllable lifestyles hazards for IHD in China, signaling the need to take effective 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, all of which are considered to pose a serious threat to IHD prevention and treatment [7,25-30]. We speculate that the diverse trends in IHD burden among different ages, sexes, and regions is most likely affected by these risk factors.
Study strengths and implications for policies
Several studies paying attention to the problems of the increased disease burden of IHD in China have been carried out. Most previous studies mainly worked at the local level with a limited time frame and failed to provide an overall temporal and geographical trend analysis which systematically considered both demographic characteristics and provincial disparities [9-11,16,17,31]. Our study revealed more comprehensive statistics in IHD burden among Chinese and subgroup populations according to age, sex, and regions, based on results derived from the advanced GBD 2016 study [2-5]. 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 the different economic levels of the various provinces of China, which would ensure that medical and health care services can be equally available. Health authorities should also pay more attention to the issue of “health inequality” affecting the Chinese population and ensure everyone must be given equal opportunities to enjoy a state of physical-and-mental health regardless of their socio-economic status, gender, ethnicity, and residency, in order to manage the IHD burden.
While it improves on previous studies, this study also has its limitations. Firstly, although our analysis of IHD burden was conducted at national and provincial levels, the disease burden at the county level and any urban-rural discrepancies were not examined. The gaps between assessments at national or 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 [32]. Although the GBD 2016 study had updated the scientific data and analytic methodology of the GBD 2015 study, changes in diagnostic technology over time periods might exert great impact on time trends of IHD, thus making inevitable measurement errors in the acquisition of data [2-5]. With regard to the estimation of YLDs, the disability weighting came from multiple national statistical results all over the world, which leads to uncertainty when estimating YLDs specifically for China [2].