The greatly increased expectancy of survival into old age is one of humanity's major achievements.1 To the contrary, worldwide population ageing and the attendant increases in public spending on health and social care are seen as a threat to worldwide economic stability in the 21st Century.2 Informed policy making and planning necessitates an understanding of the present and probable future distribution of morbidity and its effect on mortality, disability, and dependence. Several effects need to be considered; demographic and epidemiological transitions and secular changes in the effectiveness and coverage of disease control measures. Effects will vary between disorders and regions.
The worldwide epidemic of chronic diseases is strongly linked to population ageing. Disorders with a strong age-dependent relation will increase in prevalence in parallel with the absolute and relative numbers (relative to the total population size) of older people (≥60 years). In high-income countries, population ageing persists as fertility continues to fall and life expectancy increases slowly. For many middle-income countries mortality has decreased over much of the 20th century, and decreasing fertility is now ushering in unprecedented rapid population ageing. The doubling in the proportion of the population aged 65 years and older from 7% to 14%, accomplished in 46 years in the UK, 68 years in the USA, and 116 years in France, will be completed in just 26 years in China and 21 years in Brazil.3 The appendix reviews the implications for China and national policy directions.
The epidemiological transition from the age of pestilence and famine to the age of degenerative and man-made diseases is near complete in most high-income countries. Low-income and middle-income countries face various gradations of a double burden of infectious and non-communicable diseases, the balance shifting inexorably towards non-communicable diseases. A globalisation of risk behaviours; including diets rich in saturated fat and increase of tobacco use and underactivity, with consequent obesity; partly causes the rapid increase in burden of chronic diseases in these regions. After the transition, in high-income countries, cardiovascular risk factors and diseases are typically associated with economic disadvantage and low levels of education, but the trend is often in the opposite direction in low-income and middle-income countries.
Key messages
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23% the global burden of disease arises in older people (nearly half the burden in high-income countries and a fifth in low-income and middle-income countries)
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Chronic non-communicable diseases account for most of the burden; leading contributors are cardiovascular diseases, cancer, chronic respiratory diseases, musculoskeletal diseases, and mental and neurological disorders
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Population ageing will be the major driver of projected increases in disease burden in older people, most evident in low-income and middle-income countries and for strongly age-dependent disorders (dementia, stroke, chronic obstructive pulmonary disease, and diabetes). These are also the disorders for which chronic disability makes a substantial contribution to burden
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Primary and secondary prevention for cardiometabolic disorders is probably as effective in older people as it is in younger people, and the benefit is increased in view raised levels of absolute risk of adverse outcomes. Nevertheless, access and coverage is especially poor in older people
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Effective intervention in older people is complicated by ageism, complex multimorbidity, and no access to age-appropriate care, and is exacerbated by user fees, inadequate income security and social protection. Assessment and treatment needs to be holistic, coordinated and person-centred. Home-based outreach, and multidimensional assessment of frailties that might be treated or mitigated might help to reduce individual and societal effects on disability and dependence
In high-income countries, mortality from cardiovascular disease has been decreasing in all age groups. The average age of first onset and death from cardiovascular disease has been increasing and shifting the burden into older age. Decreasing incidence plays a part, but case fatality rates have also fallen with improved acute hospital management. Since prevalence is a product of incidence and duration, long survival for these and other chronic diseases has a profound effect on population burden, particularly on years lived with disability and needs for care.
In this Review, we trace these changing patterns examining present and future burden of major chronic diseases of particular relevance to older people (cardiovascular diseases [stroke and ischaemic heart disease], cancer, diabetes, chronic respiratory diseases, visual impairment, dementia, and musculoskeletal disorders) across world regions by income level and their underlying risk factors and evidence-based treatments. We complement this disorder-based approach by reviewing three cross-cutting themes; fraility, multimorbidity, and ageism in the provision of service; that distinctively characterise the interaction of ageing and health and pose challenges and opportunities to strengthen health systems to meet the needs of older people.