In this study, we evaluated the trends and burden of major CVD death in a rapidly developing society. HS, IHD and IS were the top 3 leading causes of CVD death during 1974-2015. As the leading cause of CVD immature death, HS death mainly occurred among occupational population aged 35-69 years in both sexes. Except for those unmodifiable HS risk factors include age, sex, race-ethnicity and genetics, modifiable risk factors such as hypertension, smoking, waist-to-hip ratio, diet and heavy alcohol consumption were well established [31,32]. HS is highly prevalent in LMICs where the burdens of hypertensive disorders are heavy [32]. HS accounts for <30% of stroke death in USA, whereas it accounts for 30-40% of all stroke death in China [33]. Alcohol and smoking consumptions have direct relationships with HS. The consumptions are strongly related to a specific worksite and time of shift, job stressors, and air pollution [34, 35]. Heavy alcohol and smoking consumptions are linked to hypertension and poor blood pressure control in hypertensive patients [36, 37]. Air pollution factors such as nitrogen dioxide and ozone also increase the risk of HS death via increasing the incidence of hypertension [38-40]. HS death started to decrease from 1995, possibly due to 4 reasons: first, hypertension was under the control because anti-hypertensives were covered by medical insurance in China since 1992; second, effective control of blood pressure owing to the World Bank-supported mass health promotion program in 1996 decreased HS-related death; third, pollution-causing industries were removed during the 1980s, which greatly reduced ambient pollution; fourth, medical insurance and medical reform since 1990 have got initial achievements.
IHD, the 2nd cause of CVD-related immature death during 1974-1995, ranked the leading cause of CVD deaths after 1995, which was in accord with that in the whole Chinese population [41]. Marked regional differences in epidemiological trends in age-standardized mortality of IHD have been documented in China. In 2015, the mortality from IHD in Heilongjiang province located in the north east region and Shanghai in the southeast region of China was 187.4 per 100 000 and 44.2 per 100 000, respectively [42]. This difference might be caused by relatively higher SDI, less ambient or indoor pollution in winter, higher temperature, and more advanced health care systems in Shanghai. The crude mortality of IHD kept increasing in both sexes, possibly because of the increase in the proportion of aged population [10]. Ambient pollution and consumption of red and processed meat are positively associated with the risk of IHD, possibly because of high serum non-high-density lipoprotein cholesterol concentration and systolic blood pressure; whereas regular excise like cycling is inversely associated the risk of IHD [42-45]. The age-standardized IHD mortality began to decline slowly after 1998 although population in Shanghai is aging at an unprecedented level since 1995. Improvements in medical service and healthy lifestyle promotion should be effective in decreasing IHD death. IS has been associated with low income, low education levels, hypercholesterolemia, physical inactivity, smoking, and obesity [46-48]. IHD and IS had been recognized as a single type of CVD called ischemic disease in international guidelines because they shared pathologies and risk factors, and shared strategies for primary and secondary prevention [18]. Ischemic disease increased with increased total cholesterol and decreased with elevated high-density lipoprotein cholesterol [49]. The trend in ischemic disease is affected by aging, SDI, lifestyle change, and the quality of medical care. Smoking led to a 63% higher risk of ischemic disease in urban male smokers [50]. A study of the China Kadoorie Biobank has demonstrated that individuals in the top quintiles of physical activity have a 23% lower risk of major ischemic events than those in the bottom quintiles [51]. Compared to people who never or rarely ate fresh fruit, people consuming fresh fruit daily had a 34% lower risk of IHD and a 25% lower risk of IS [52]. Total IHD death had been decreased significantly since the Chinese government issued the “National Physical Fitness Program” in 1995. Pledging sports and health-building services would be aligned with national economic development. Residents in Shanghai kept the habit of daily consumption of fresh vegetables and fruits during the 42 years, the proportion of daily consumption varied from 34% to 39%, which may contribute to changes in CVD mortality curves (Figure S2 in Additional file). The mechanisms by which fruits and vegetables protected CVD death include not only some known bioactive nutrient effects, but also their functional properties including reducing antioxidant stress, improving plasma lipoproteins, lowering blood pressure, improving insulin sensitivity, and regulating hemostasis [53]. These evidences indicate that ischemic CVD should be prevented via improving lifestyles such as quitting smoking, increasing physical activity, and consuming fresh vegetables and fruits.
RHD, the main cause of CVD deaths in children and young adults in LMICs, results from an abnormal autoimmune response to a group A streptococcal infection [54]. Preventive measures, based on antibiotic treatment especially penicillin use, are very efficient. Thus, RHD reflects a poor socioeconomic condition that lead to lack of medical resources. With steady socioeconomic growth during 1974-2015 in Shanghai, death from RHD kept decreasing rapidly.
In this study, we found that death of hemorrhagic CVD, ischemic CVD, and myocardial valvular CVD increased in population born during 1937-1945 and increased again in those born during 1958-1965. This might be caused by early life exposure to serious adverse condition especially malnutrition during the Japanese military occupation (1937-1945) and the Chinese Famine (1958-1961), respectively. Exposures to adverse living condition and malnutrition in early life are often associated with metabolic syndrome including hyperglycemia, hypertension, and type 2 diabetes that contribute to an increased occurrence of CVD in later life [55-58]. Thus, to decrease adverse events including malnutrition in early life should be important for the prevention of the major types of CVD in later life.
Over the 42-year study period, a reduction in the age-standardized CVD mortality was greater in women than in men. The age-standardized mortality rate and SYPLL of CVD kept decreasing in women after 1977 and declined sharply after 1998 but did not decline anymore in men, which is consistent with a previous observation in China [59]. In the 21st century, HS, IHD, and IS have become the 3 main lifetime threats to men and shown a growing trend, suggesting that specific research and health promotion strategies of CVD for men should be brought to attention. This sex disparity is possibly caused by different levels of risk factor exposure. In China, men are more likely to be exposed to factory air pollution, tobacco smoking, and alcohol abuse [60]. Smoking cessation and alcohol restriction should be effective in controlling more CVD-caused immature death in men.
Further, SCD will be the leading cause of CVD during 2025-2029. This suggests that with the improvement of medical services, the first episode of CVD rarely lead to death, and turn into sequelae stage, which will prolong lifetime but may reduce the healthy life year. It also weakens the quality of life and aggravates the burden, hence the urgent need for effective rehabilitation care to prevent disability caused by sequelae of CVD in the future.
This study has major strengths including a stable and large population, a social context of rapid economic development and intensive change of the policies, and stringent mortality ascertainment. However, there are certain limitations to be acknowledged. First, although death registration in Yangpu is one of the high-quality systems in China, the death certification was too precise to assign CVD subtypes using ICD codes, only 7 causes of CVD deaths were demonstrated, other CVD subtypes were grouped as “other cardiovascular and circulatory diseases”. Second, lifestyle, disease history, and medical care data were not included in this system, so it was impossible to quantitate the associations of the risk factors with CVD death.
Conclusively, although the trends in cause-specific mortality and burden of CVD in urban Shanghai have generally declined during 1974-2015, the threat of CVD to human life is still the primary concern. Exposure to adverse event and malnutrition in early life contributed to an increase in CVD death. It is necessary to improve air quality, strengthen health education, advocate smoking cessation, restrict alcohol consumption, and popularize reasonable diet. Medical insurance and improvement in medical service are important for the prevention and control of CVD death. Effective rehabilitation is needed to prevent the disability caused by sequelae of CVD.