A life-course approach to health: synergy with sustainable development goals

Abstract A life-course approach to health encompasses strategies across individuals’ lives that optimize their functional ability (taking into account the interdependence of individual, social, environmental, temporal and intergenerational factors), thereby enabling well-being and the realization of rights. The approach is a perfect fit with efforts to achieve universal health coverage and meet the sustainable development goals (SDGs). Properly applied, a life-course approach can increase the effectiveness of the former and help realize the vision of the latter, especially in ensuring health and well-being for all at all ages. Its implementation requires a shared understanding by individuals and societies of how health is shaped by multiple factors throughout life and across generations. Most studies have focused on noncommunicable disease and ageing populations in high-income countries and on epidemiological, theoretical and clinical issues. The aim of this article is to show how the life-course approach to health can be extended to all age groups, health topics and countries by building on a synthesis of existing scientific evidence, experience in different countries and advances in health strategies and programmes. A conceptual framework for the approach is presented along with implications for implementation in the areas of: (i) policy and investment; (ii) health services and systems; (iii) local, multisectoral and multistakeholder action; and (iv) measurement, monitoring and research. The SDGs provide a unique context for applying a holistic, multisectoral approach to achieving transformative outcomes for people, prosperity and the environment. A life-course approach can reinforce these efforts, particularly given its emphasis on rights and equity.


Introduction
The right to the highest attainable standard of health for all people, is enshrined in the World Health Organization's (WHO) constitution and in the United Nations' (UN's) human rights framework. 1,2 Subsequent international declarations emphasize that health is interlinked with peace, development and the environment. 1,3-6 The UN's Sustainable Development Goal 3 (SDG 3) for 2030 is to "ensure healthy lives and promote well-being for all at all ages". 7 Adoption of the SDGs provides a unique opportunity to apply a holistic, people-centred, multisectoral approach to health and development, which is well aligned with a life-course approach to health. [8][9][10][11][12] Properly applied, a life-course approach can help realize the vision of SDG 3, ensure universal health coverage (UHC) and achieve health and well-being for all at all ages.
To take advantage of this unique opportunity, we commissioned two reports on the evidence supporting a life course approach to health to inform policy and practice in the SDG era. The first focused on conceptual and operational implications and the second on epidemiology and the risk of chronic disease. 13,14 These evidence syntheses showed that there remain barriers to implementing a life-course approach. There needs to be a better, shared understanding of how individuals' health and well-being are shaped by multiple factors and how the risk of ill health can accumulate across life stages and generations. [8][9][10][13][14][15][16] One obstacle is the current focus on single diseases or specific age groups, rather than holistically addressing health throughout life. Operational constraints include frequent shifts in political priorities, short-term policy and funding cycles, poor coordination between the actions of health care and other sectors of society in addressing social and environmental change (which may threaten both health and sustainable development) and limited measurement of health and well-being across individuals' lives and generations. [12][13][14]17 In addition, the evidence syntheses found that most studies of the life-course approach focused on noncommunicable diseases and healthy ageing in high-income countries -few considered other health topics, younger age groups or low-and middle-income countries. 13 Further, the predominant themes were theoretical, epidemiological, research-based and clinical, with limited application to policy, planning and programme implementation. 13,14 The aim of this article is to show how a life-course approach can be extended to all health topics, age groups and countries by building on a synthesis of existing scientific evidence, experience in different countries and advances in health strategies and programmes. Aligned with the SDGs and UHC, a life-course approach can facilitate the integration of individual, social, economic and environmental considerations. 7 As recommended by the Lancet Commission on Planetary Health, operationalizing a life-course approach will involve "integrating the aim of sustained improvements in human health and well-being with the preservation of key natural systems, supported by good governance and appropriate policies". 17 First, we provide a conceptual framework for a life-course approach by presenting definitions of the key concepts required to build shared understanding -a prerequisite for collective action. 9,10,13 This conceptual framework was developed by analysing and thematically categorizing the findings of the two evidence synthesis reports, which reviewed more than 200 publications, using a qualitative, narrative synthesis method. 13,14,18 The conceptual framework was based on WHO's World Report on Ageing and Health. 15 Its approach to healthy ageing was extended to other age groups and health topics through consultations across WHO departments that took into account scientific and conceptual advances and updates in global strategies and programmes. [8][9][10]16,19 Our synthesis method followed a multigrounded theory approach and included deductive and inductive analyses and triangulation of the different methods. 20 Particular attention was paid to the implications of implementing a life-course approach to help achieve UHC and realize the SDGs.

Conceptual framework
As we defined it, life course approach to health optimizes the functional ability of individuals throughout life, enables well-being and realization of rights, and recognizes the critical interdependence of individual, intergenerational, social, environmental and temporal factors. Fig. 1 depicts the conceptual framework we developed. It is important to provide clear definitions of key concepts, such as: (i) functional ability; (ii) intrinsic capacity; (iii) well-being; (iv) the realization of rights; (v) life stage; (vi) resilience; (vii) risk; and (viii) the social and environmental determinants of health.
The main outcome of the life-course approach to health is functional ability, which is the sum of the individual and environmental attributes that enable a person to be or do what they have reason to value. 10 Functional ability enables well-being at all ages and is interdependent with the realization of rights. For a neonate or infant, functional ability could be manifested by feeding well and playing; for older adults, by the ability to function independently without dependence on care. Functional ability is determined by the individual's intrinsic capacity and physical and social environments and by the interaction between the individual and these environments. 10 Intrinsic capacity is the sum of all physical and mental (including psychological) capacities. 10 The con-cept of functional ability is consistent with the International Classification of Functioning, which defines functioning as a composite term for body functions and structures and the individual's activities and participation. 21 Additionally, functional ability takes into account the interaction between, and the interdependence of, individual, social and environmental determinants of health and the individual agency and collective actions required to ensure health and well-being throughout life. In Fig. 1, functional ability and intrinsic capacity are depicted as idealized arcs across the life course. Intrinsic capacity follows a biologically determined trajectory of physical and mental capacities. In contrast, functional ability can be optimized throughout life by a supportive environment. The vertical bars in Fig. 1 indicate that functional ability and intrinsic capacity can vary across a range at all life stages. This variability depends on the individual's circumstances and on the critical events that influence health trajectories.
Well-being is a subjective state that can be evaluated across three domains: (i) perceived life satisfaction; (ii) emotions experienced; and (iii) self-realization and a sense of purpose or meaning. 22 A meta-analysis of longitudinal studies indicated that subjective well-being is associated with lower mortality. 22 Good health depends on, and enables, the realization of rights. 2,23 Desired health outcomes should be achieved by applying human rightsbased, gender-responsive and equitydriven approaches to policy-making and programme implementation. In addition to fulfilling legal obligations, this will help ensure better and more equitable health outcomes. 24,25 On life stages, there are differing perspectives and a need for clarity. For example, questions exist about whether life begins at birth or earlier, about the most appropriate age ranges for different stages and about the specific events that influence health trajectories throughout life. Life stage definitions are influenced not only by chronological age, but also by sociocultural norms and the individual's functional status. 13,14 For practical reasons and for programming purposes, here the  life course is regarded as starting at birth. Our timeline in Fig. 1 covers four broad stages: (i) birth, the neonatal period and infancy; (ii) early and later childhood and adolescence; (iii) youth and adulthood; and (iv) older adulthood. These four stages are based on programming approaches used in global health strategies. [8][9][10]16,19 The preconception period and pregnancy, which occur during the reproductive years, are also important times during the life course. They can affect the next generation, as reflected in intrinsic capacity at birth. Resilience to ill health and the risk of ill health accumulate throughout life and across generations. 13,14 For example, 70% of preventable deaths from noncommunicable diseases in adults have been linked to risks encountered, and behaviours that started, during adolescence. 26 In particular, 50% of mental health problems are established by the age of 14 years and 75%, by the age of 24 years. 27 In addition to the critical events that shape an individual's health trajectory, the number and sequence of exposures to risk and periods of increased susceptibility -some of which occur before birth or are genetically inherited -are also crucial. [12][13][14]16 Social and environmental determinants of health include health systems, essential public health functions, multisectoral factors and cross-sectoral actions. There is evidence linking people's health and well-being to poverty reduction, education, access to clean air and water, the realization of human rights and sustainable livelihoods and environments, all of which are underpinned by good governance. 7,17,25,[28][29][30] The individual good and social good are mutually dependent and both are underpinned by the physical environment. Taking this interdependence into account requires a paradigm shift in health and development policies and programmes. 9,10,17,30,31

Implications for implementation
The implementation of a life-course approach to health involves four areas: (i) policy and investment; (ii) health services and systems; (iii) local, multisectoral and multistakeholder action; and (iv) measurement, monitoring and research.

Policy and investment
A life-course approach requires holistic, long-term, policy and investment strategies that promote better health outcomes for individuals and greater health equity in the population -the two are interlinked. 30 For example, since 1995 the Australian Longitudinal Study on Women's Health has provided evidence of how gender and health inequities accumulate throughout life: women who struggled to manage financially before the age of 20 years had an increased risk of reduced physical capacity in later life and their physical decline started earlier. 15 To counter this, the government updated its policy to ensure age-appropriate health care and address inequities across the life course. 13,15 Long-term investment in a lifecourse approach can provide high returns for health and sustainable development, both by limiting ill health and the accumulation of risk throughout life and by contributing to social and economic development. For example, in 2013 it was reported that 11% of recent economic growth in low-and middleincome countries resulted from a reduction in preventable deaths. 32 Investment in early childhood, child and adolescent health and development can yield a benefit-to-cost ratio of 10-to-1 in health, social and economic benefits and rates of mental health disorders and noncommunicable diseases in later life can be reduced. 26,27,33,34 In 2014, an analysis indicated that a comprehensive package of family planning, quality-of-care improvements in pregnancy and childcare and the prevention and management of childhood illnesses would yield 9 United States dollars in economic and social benefits in low-and middle-income countries for every dollar spent. 35 For older people, integrated health, social and environmental investment can help reduce health-care costs and care dependency and promote well-being. 36 Investment in evidence-based interventions can also improve resilience and mitigate risks throughout life and across generations. 9,10,13,14,19 Despite the evidence supporting disease prevention, in 2015 the Organisation for Economic Co-operation and Development (OECD) estimated that spending on prevention had decreased since 2009 in around half of OECD countries, whereas spending on longterm, outpatient and inpatient care continued to grow. 37 Much more focus is required on preventing health risks and reducing their cumulative effect throughout life and across generations, and to avoid prohibitive health-care costs. Further, domestic health expenditure and development assistance for health have tended to prioritize specific diseases or life stages over others. 38 A more holistic, long-term approach to policy and investment is required to operationalize a life-course approach to health, thereby helping to ensure UHC and realize the SDGs.

Health services and systems
Properly implemented, a life-course approach can improve the effectiveness and reach of UHC. Planning for a life-course approach to health should coincide with national planning to achieve UHC, preferably in a people-centred manner. For example, integrating services holistically to address people's health and well-being, rather than focusing on specific diseases or issues, can yield better health outcomes and improve efficiency. 39 A two-year study of health sector reform in China highlighted the value of people-centred integrated care for ensuring better health for the population at all ages: quality of care was enhanced, individuals and families experienced better care and the cost was affordable for both individuals and government -all factors critical for UHC. 40 Countries should themselves ascertain how best to implement UHC to ensure highquality and accessible services and provide financial protection that matches the unique health-care needs of their populations. 19 These needs are detailed in Fig. 2, which shows the core UHC framework, comprising health-care needs and health services and systems, and includes consideration of life stages and the enabling environment.
Health systems strategies such as integrated people-centred health services can contribute to operationalizing the life-course approach and to implementing UHC. 41 A strong health-care system is essential and WHO proposes an approach to improving system performance that will help it evolve and respond to emerging challenges. This approach has three elements: (i) strengthening the foundations of the health system; (ii) setting a coherent institutional framework; and (iii) supporting transformation. 42 In addition, essential public health functions, which constitute a country's minimum public health requirements in areas such as governance, disease control, health promotion and health research, 43 are important for linking actions in health and other sectors. All these elements require investment in, and the development of, a dedicated health workforce.

Local action
Global strategies and national policies have to be translated into local actions to achieve the desired outcomes. Actions across different sectors of society can have a synergistic effect in improving health, reducing poverty, improving education and gender equality and promoting socioeconomic and sustainable development. 7,25 Cross-sectoral programmes involving health and other sectors are key. For example, the Madsen's Institute for Tribal and Rural Advancement programme in India used a life-course approach with cross-sectoral programmes to transform the health of, and prospect of sustainable development for, people in 48 villages in Orissa. 44 The programme, which was led by local communities along with local health services and government, started with malaria control and expanded, according to the communities' needs, to include other health, educational, environmental and poverty-reduction goals, because these were recognized as interdependent. The result was a range of health, social and developmental advances and the infant mortality rate halved over 15 years, though it remained extremely high in neighbouring villages not covered by the programme. 44 Policy and implementation efforts across different sectors can be coordinated by applying, for example, the Health in all Policies approach 25 and multistakeholder policy dialogue. 45 These techniques can help promote accountable and participatory governance and the institutionalization of crosssectoral programmes and multistakeholder partnerships, in alignment with the SDGs. Political leadership is critical for assuring an integrative, multisectoral approach. 7,25 Many countries have made progress towards achieving UHC and improving health and sustainable development using strategies aligned with these implementation techniques: Brazil, Chile, China, Cuba, Rwanda, Thailand and subnational regions such as Kerala in India have strengthened health systems, broadened access to health services and provided progressive financing to expand UHC. 28,46 These countries and others made progress by also addressing inequities in, and the social and environmental determinants of, health. 7,25,28,46

Measurement, monitoring and research
Better understanding of the life-course approach to health, which can be obtained from both objective measures and people's subjective experience, can guide individual and collective efforts to improve functional ability at all ages. In particular, more information is needed on how greater life expectancy in some populations affects individuals' health and well-being in later life. Several key issues influencing measurement, monitoring and research should be considered.

Outcomes
New international standards incorporating a core set of indicators applicable to all life stages are needed to improve the measurement of life-course variables. 12,13 Age Chronological age may not accurately represent biological, social, psychological or functional age or an individual's experience of ageing. 12,13 Clearer information on age ranges for specific life stages and on how to identify critical phases and pathways would enable key services to be targeted more effectively.

Determinants of health
The focus should be on determinants that are modifiable or amenable to change. Determinants that shape a particular life stage or influence health throughout life should be identified and monitored. 36

Change in functioning and interventions
Identify and measure both factors that can cause a decline in functioning or well-being and those that can reverse that decline (e.g. reducing air pollution) and determine how this knowledge was obtained. Identify interventions likely to produce the greatest gains at different life stages.

Critical pathways and complex systems
A unified measurement approach is needed to take account of the wide variety of life course variables. 10,13,14 This should include metrics for analysing the life course, measures of people-centred services and patient-reported outcomes.

Equity
Increased understanding is needed of how and why some people and groups experience unequal access to services, resources and power and have restricted rights and freedoms. Data should be collected from, for example, statistical surveys, administrative records and human rights reports. Engagement with

Research studies
Substantial investment in birth cohort, longitudinal and intervention studies is needed, particularly in low-and middleincome settings. 13,14,47 Past examples include WHO's Study on global AGEing and adult health (SAGE) in six low-and middle-income countries 48 and the Longitudinal Ageing Study in India (LASI). 49 Assuring long-term investment in cohort studies across the life course can be challenging, as in the 30-year Pelotas birth cohort study in Brazil. 50

Country information systems
High-quality data on health, health equity and social and environmental determinants of health across the life course are needed, along with the capacity to analyse, communicate and use the data for policies and programmes.

Implementation research and knowledge exchange
Research policy and new research should be aligned to support and understand the implementations of the life-course approach. The exchange of knowledge between countries should be promoted. Table 1 provides examples of how SDGs, which have already been integrated into monitoring frameworks in many countries, can be aligned with the life-course approach. Indeed, the life-course approach is relevant to many SDGs. However, more work is required to improve the tracking of individuals' functional ability and health trajectories, including the accumulation of resilience and risk throughout life and across generations. It will also be important to determine how countries use this information to take appropriate actions and to achieve better outcomes.

Qualitative studies
Such studies are needed to gain an insight into the context-specific, individual, sociopolitical, cultural, economic and environmental factors that influence health and well-being throughout life, some of which may otherwise be overlooked or poorly understood. 13

Conclusion
A life-course approach to health can help shape UHC and wider ambitions for health and the SDGs in several ways. First, and by definition, a lifecourse approach is central to ensuring the health and well-being of all people at all ages (SDG 3). Second, this approach recognizes the interdependence of people, prosperity and the environment and can be employed to implement multisectoral actions for achieving shared goals. Third, it can inform country-specific planning for UHC and bring together elements of many existing national, regional and global health and development strategies. Fourth, it emphasizes rights, gender equality and equity, thereby ensuring no one is left behind -a central tenet of the 2030 agenda for sustainable development. The usefulness of the life-course approach for helping countries address critical, interdependent factors affecting health and sustainable development in a holistic manner means that it fits perfectly with efforts to achieve UHC and to realize the SDGs. However, translating this approach into actions will involve overcoming numerous constraints and will require more work by stakeholders across many sectors of society.