Analysis of epidemiological trends in chronic diseases of Chinese residents

Following the population aging in China, dramatic changes have been observed in the spectrum of diseases among Chinese residents. E.g., the incidence and prevalence of chronic diseases, such as cardiovascular, cerebrovascular, metabolic, and respiratory diseases, are constantly growing. Additionally, osteoporosis, sarcopenia, and chronic renal disease have gradually become common chronic diseases among the elderly. Chronic diseases in the elderly have ranked first in the spectrum of diseases among Chinese residents. Therefore, understanding the trends of main chronic diseases among Chinese residents and developing proactive countermeasures have become a major public health issue for China.

most significant risk factors for cardiovascular and cerebrovascular diseases among the Chinese, and is associated with more than half of the incidence and mortality related to cardiovascular and cerebrovascular diseases. 13 Furthermore, more Chinese residents died of cardiovascular and cerebrovascular diseases than other reasons during these years, 14 so such diseases are regarded as major threats to the health of Chinese residents. As a result, curbing hypertension is the crux in the prevention and treatment of cardiovascular and cerebrovascular diseases. The crude prevalence (adjusted) rates of the population aged 15 years and older in five national sample surveys on hypertension conducted in China in 1958-1959, 1979-1980, 1991, 2002, and 2012 were 5.1%, 7.7%, 13.6%, 18.8%, and 25.2%, respectively. It can be concluded that the prevalence of hypertension among Chinese adults has clearly been on the rise, despite the discrepancy in the survey scope, total respondents, age, and diagnostic criteria. 15 Additionally, according to the data from surveys on hypertension collected from 450 000 people across 31 provinces, municipalities, and autonomous regions in China from 2012 to 2015, the crude prevalence rate of hypertension among the population aged 18 years and older was 27.9%. Furthermore, the data also showed that the prevalence of hypertension in largeand medium-sized cities remained high. At the same time, it substantially increased among the rural population, where it reached even higher levels than those observed among the urban population. The prevalence of hypertension among adults substantially increases as they age. For example, nearly one-third of the population aged 45-59 years, and half of the elderly suffer from hypertension. Nevertheless, it is worrisome that the rates of awareness, treatment, and control of hypertension are very low while the prevalence, disability, and mortality rates are high. Such rates of hypertension in Chinese adults sharply increased as the policy on medical reform was put in place during recent years. For example, China's hypertension survey from 2012 to 2015 16 showed that the rates of awareness, treatment, and control of hypertension among residents aged 18 years and older were 46.9%, 40.7%, and 15.3%, respectively. Despite an increase in such rates in 2002, the rates of awareness and treatment of hypertension were <50%, and the rate of control was even lower, far lagging behind those in developed countries. 17 The prevalence of hypertension in China continues to increase and is not effectively controlled. Furthermore, hypertension is an important risk factor for cardiovascular and cerebrovascular diseases. It is anticipated that the prevalence of hypertension and its cardiovascular and cerebrovascular complications in China will continue to rise over an extended period of time. As a result, it is all the more urgent to increase efforts in the prevention and treatment of hypertension, which is expected to be one of the most crucial public health issues among Chinese residents in coming years. As mentioned, the mortality rate for CHD in rural residents has substantially increased, surpassing that of urban residents. Furthermore, China has an expansive agricultural industry with a large rural population and high morbidity, so it should make every endeavor to enhance the prevention and treatment of CHD for rural residents.

| CEREB ROVA SCUL AR D IS E A S E S
Stroke is the second-leading cause of death among those 60 years and older in China, and has become a global public health issue due to its high rates of incidence, disability, and mortality. 18 Over recent years, China has witnessed a rapid development of cerebrovascular diseases, with high prevalence and disability rates and increased medical expenses. Consequently, such diseases have placed an enormous financial burden on individuals, families, and society. China conducted a large-scale epidemiological survey on cerebrovascular diseases as early as in the 1980s, which was comparable to the epidemiological surveys conducted over recent years due to the basic consistency in survey methods and diagnostic criteria. In 1982, the age-standardized prevalence of stroke among residents in six major Chinese cities was 719/100 000, the incidence was 205/100 000 people per year, and the mortality rate was 109/100 000 people per year. In 1985, the age-standardized prevalence of stroke among rural residents in 21 Chinese provinces and cities was 394/100 000, the incidence was 172/100 000 people per year, and the mortality rate was 132/100 000 people per year. 19,20 The prevalence (crude) rate of stroke among people aged over 60 years in 1992 was 7.9%, which increased to 12.  22 The survey indicated that the prevalence (crude) rate of stroke in China was around 1287/100 000, which was a dramatic growth from 30 years ago. Furthermore, the prevalence of stroke among men over 40 years was significantly higher than that among women over 40 years, and that among the rural population gradually overtook that among the urban population. Currently, approximately 11 million patients suffer from stroke in China, aside from asymptomatic cerebral infarction, according to the estimate of prevalence by this epidemiological survey. In light of an epidemiological survey on cerebrovascular diseases among 600 000 Chinese residents conducted in 2013, the incidence (crude) rate of stroke was 274/100 000 people per year. Specifically, the incidence (crude) rates of stroke among the rural and urban populations were 227/100 000 people per year and 168/100 000 people per year, respectively, while the prevalence of asymptomatic cerebral infarction was about 19.9%.
Compared with three decades ago, the incidence of stroke among rural residents sharply increased by 32%, whereas among urban residents, it had increased by 18.1%. Furthermore, people were suffering from stroke at an earlier age. 20,22 In the meantime, this survey demonstrated that the death (crude) rate of stroke was 126/100 000 people per year. Specifically, the death (crude) rates among rural and urban populations were 117/100 000 people per year and 75/100 000 people per year, respectively, which was 11% and 31% lower compared to 30 years ago. Additionally, an epidemiological study among 15 000 urban residents in Tianjin that lasted for over two decades 23 illustrated that the average annual incidence rate of an individual's first stroke in 1992-1998, 1999-2005, and 2006-2012 was 124/100 000 people per year, 190/100 000 people per year, and 318/100 000 people per year, respectively. It was estimated that the incidence would grow by about 6.5% a year, with the greatest increase in men aged 45-65 years.
An epidemiological survey of cerebrovascular diseases among 600 000 Chinese people in 2013 20,22 showed that ischemic stroke, cerebral hemorrhage, and subarachnoid hemorrhage represented 70%, 24%, and 4% of the total strokes, respectively. In addition, the incidence of a cerebral hemorrhage in China was far higher than that in the United States. The incidence rates of ischemic China Chronic Disease and Risk Factor Surveillance (CCDRFS), the age-standardized prevalence of TIA in China was around 2%, while the awareness and treatment rates were <10%. Additionally, TIA was a precursor to stroke, so proactive intervention could effectively prevent the incidence of stroke. 24 By 2013, the age-standardized mortality of stroke among Chinese residents had dropped by 21% from 1990. Specifically, the mortality of ischemic stroke increased by 29%, while that of hemorrhagic stroke dropped by 38%, which may be due to the prevention and treatment as well as primary prevention of hypertension.
The prevalence of cerebrovascular diseases in China remains high and continues to rise; however, the mortality rate seems to have dropped, due to China's proactive prevention of cerebrovascular diseases. It is noteworthy that the age at onset of stroke has reduced in China, indicating that attention should be paid to the elderly and also to the prevention and treatment of cardiovascular and cerebrovascular diseases among young and middle-aged residents.
More proactive and effective strategies should be developed for screening, awareness, prevention, and treatment of TIA. Given the rapid increase in the incidence of cerebrovascular diseases among rural residents, great importance should also be attached to the intervention mode among rural populations to minimize the damage of such diseases to the health of Chinese residents as well as the society and economy.

| ENDO CRINE AND ME TABOLI C DISE A SE S
Over the past four decades, due to the aging of the Chinese population and changes in lifestyles, diabetes has developed from a rare disease into a common and frequently occurring disease. China has carried out plenty of large-scale epidemiological surveys on diabetes nationwide and the prevalence of diabetes soared to 10.4% in 2013 from 0.67% in 1980. In 1980, the epidemiological data from 300 000 people across 14 Chinese provinces and cities suggested that the prevalence of diabetes among all age groups was only 0.7%. Over the past decades, the prevalence of metabolic-related chronic diseases (eg, diabetes, obesity, and hyperlipidemia) has remained high and shows a clear onward trend. It is therefore anticipated that such diseases will remain common chronic diseases among Chinese residents in future. Not only does this represent a grave threat to health, it also increases medical expenses and the burden on medical care, society, and the economy. Accordingly, the current focus should be on the control of metabolic-related chronic diseases and on minimizing the incidence of relevant complications.
Lowering the incidence and prevalence of such diseases remains the primary goal in upcoming years.

| RE S PIR ATORY D IS E A S E S
Chronic respiratory diseases, represented by chronic obstructive pulmonary disease (COPD), result in a heavy economic burden. It was estimated that COPD would become the third leading global cause of death by 2020, second only to ischemic heart disease and cerebrovascular disease. As the population is aging faster than ever, COPD has also become one of the principal causes of dis-  Chinese residents aged 40-49 years were 32.9% and 3.2%, respectively; those of osteopenia and osteoporosis among Chinese residents aged over 50 years were 46.4% and 19.2%, respectively; and the prevalence of osteoporosis among Chinese residents aged over 65 years was 32.0%, where women and rural residents had significantly higher rates than men and urban residents. 43 The prevalence of osteoporosis in Chinese residents was high, while their awareness of such disease was seriously inadequate. The survey demonstrated that the awareness rates of osteoporosis among patients aged [40][41][42][43][44][45][46][47][48][49] years and over 50 years were 0.9% and 7.0%, respectively. The detection rates of BMD and awareness rates of osteoporosis were low because residents, especially the senior residents, had an insufficient understanding of the importance and harm of osteoporosis.

| MUSCULOS K ELE TAL D IS E A S E S
Moreover, they received treatment only when enduring serious complications, thereby missing the best opportunity for the prevention and treatment of osteoporosis.
The mass and strength of skeletal muscles vary with age, peak in young and middle ages, and then drop as one gets older. Specifically, muscle mass decreases by 1%-2% after 50 years of age, while muscle strength declines by 1.5%-3%. Furthermore, the total amount of muscle is reduced by 30% by 80 years and is accompanied by greater reductions in muscle power and strength. 44 The prevalence  who were over 60 years old suggested that the prevalence rates of sarcopenia among male and female residents were 6.4% and 11.5%, respectively. These rates were 9.3% and 4.1% among elderly men and women in Taiwan, China, respectively. 49   in China by 2007, resulting in a prevalence of 51.7/1 000 000. 56 In 2008, the number of patients with ESRD grew to 103 000 in 2008, and the prevalence was 79.1/1 000 000. 56 Thereafter, the incidence of ESRD surged in China, and the patients receiving RRT exceeded 300 000 by the end of 2014. 57 Over recent years, the prevalence of CKD has been on the rise in China. Especially high rates were observed among senior citizens due to their advanced age, thereby substantially affecting their health and quality of life. In addition to enhancing awareness and curbing the diseases of the kidney system, China should take proactive measures to control diseases that are likely to cause CKD complications, such as hypertension and diabetes, administer drugs rationally, and reduce the damage to the kidney system.

| SUMMARY
Health is a crucial aspect of human development that provides a basis for economic and social development. Improvement in health care represents an important achievement in our efforts to build a stronger nation and achieve greater prosperity. It is also a shared expectation of the public. 2 As China becomes an aging society due to the rapidly aging population, the lifelong health of all is the ultimate goal. Recent years have witnessed numerous changes in the spectrum of disease among Chinese residents. The incidence and prevalence of chronic diseases, such as cardiovascular, cerebrovascular, metabolic, and respiratory diseases, are constantly growing.
Additionally, osteoporosis, sarcopenia, and chronic renal disease When the strategy of "Healthy China" is put in place, it is necessary to grasp the epidemiological trends of chronic diseases and the status of prevention and treatment in China and to explore solutions and countermeasures in a bid to offer references for the prevention and treatment of such diseases. 4