Liu Y, Yang G, Zeng Y, Horton R, Chen L.
Policy dialogue on China's changing burden of disease.
Lancet. 2013 Jun 8;381(9882):1961-2.
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The Lancet article by Chan and colleagues is the most comprehensive epidemiological assessment thus far of dementia and its major subtypes (Alzheimer’s disease and vascular dementia) in mainland China. It provides estimates on major measures of epidemiology, for example, prevalence, incidence, and mortality, as well as the disease burden (absolute number of cases) in China. Martin Prince’s comment on this study is excellent.
Dementia is very much an age-dependent disorder; after 65 years of age, both prevalence and incidence rates double every five years. Approximately one in two persons aged 95+ is affected by dementia in a Swedish study (von Strauss et al., 1999), which is confirmed in this study of people in China.
This study showed a slight increase in the age-specific prevalence of dementia from 1990 and 2000 to 2010, which is likely due to methodological issues and increased awareness of dementia by the public and by health professionals. The dramatic increase in the absolute number of patients with dementia over the whole period is likely to be driven by a steadily increasing aging population. Indeed, according to the World Bank, the life expectancy at birth in China was 69 years in 1990, 71 years in 2000, and 73 years in 2010, and the proportion of people age 65+ was 6 percent in 1990, 7 percent in 2000, and 8 percent in 2010.
Over the last few decades and in the future, China faces a rapidly increasing older population, driven primarily by low fertility owing to the long-term one-child policy since the late 1970s and by a substantial increase in life expectancy owing to a decline in late-life mortality as a result of social development and fast economic growth since the 1980s. In recent years, the quick urbanization in China has further accelerated the process of population aging (Gong et al., 2012). In this context, China will face even bigger challenges owing to an older population and dementia than other countries in the world. This is supported by comparing the analysis by Chan et al. to previous studies. For instance, a 2005 Lancet article estimated that the number of people with dementia worldwide would double about every 20 years from 2001 (Ferri et al., 2005), whereas Chan and colleagues’ analysis suggested that the number of patients with dementia in China almost tripled in 20 years from 1990 (3.68 million) to 2010 (9.19 million). In addition, worldwide the number of patients with dementia increased by 46.5 percent, from 24.3 million in 2001 (Ferri et al., 2005) to 35.6 million (Alzheimer Disease International 2010 report), while Chan et al. estimated that in China it increased by 63.5 percent, from 5.62 million in 2000 to 9.19 million in 2010.
To deal with the fundamental challenges of population aging and dementia in China, some key areas need to be further explored: 1) development of a healthcare system covering elderly people living both in urban and rural regions, and 2) development of effective interventions that postpone the onset of dementia and late-life cognitive impairment. The latter is critical to fundamentally reducing the burden of the disease. According to research in Western societies, cardiovascular risk factors (e.g., hypertension, diabetes, obesity) and related disorders (e.g., stroke and coronary heart disease) are important determinants of dementia. Some of these factors and disorders have declined since the 1970s among traditional high-income nations. By contrast, the prevalence of most of these factors and disorders has increased in China, especially with regard to hypertension, diabetes, obesity, and stroke. Intervention strategies targeting these metabolic risk factors are likely to be effective in reducing the risk of dementia or in postponing its onset.
Action items could include national campaigns against chronic, non-communicable diseases that target unhealthy lifestyles and cardio-metabolic risk factors. They would likely reduce the risk of dementia and late-life cognitive impairment as well. Increasing research personnel and boosting the financial investment in research on the health care of elderly people and on specific intervention strategies against dementia would help. In particular, focusing on psychosocial, social-cultural, and vascular risk factors might prove most beneficial.
von Strauss E, Viitanen M, De Ronchi D, Winblad B, Fratiglioni L.
Aging and the occurrence of dementia: findings from a population-based cohort with a large sample of nonagenarians.
Arch Neurol. 1999 May;56(5):587-92.
Gong P, Liang S, Carlton EJ, Jiang Q, Wu J, Wang L, Remais JV.
Urbanisation and health in China.
Lancet. 2012 Mar 3;379(9818):843-52.
Ferri CP, Prince M, Brayne C, Brodaty H, Fratiglioni L, Ganguli M, Hall K, Hasegawa K, Hendrie H, Huang Y, Jorm A, Mathers C, Menezes PR, Rimmer E, Scazufca M, .
Global prevalence of dementia: a Delphi consensus study.
Lancet. 2005 Dec 17;366(9503):2112-7.