Rationale for the Healthy Ageing Toolkit

The world’s population is ageing. In 2023, 8.5% of people worldwide are aged 65 and over. By 2050, this is projected to double to 16% of the global population. Most people aspire to live a long life and many government interventions focus on maximising lifespan. However, if the extra years of life are dominated by a rapid decline in physical and mental capacity, older people’s health will be limited putting at risk their quality of life and creating broader societal risks in terms of financial and social costs. Thus, maximising healthspan, the period that an individual spends in a state of health, is a key public health goal.

Ageing is shaped by physical, social, economic, and environmental factors across the life-course. Reflecting this, the WHO 2015 Report on Ageing and Health proposed a new concept of healthy ageing, oriented around an individual’s functional ability rather than the presence or absence of disease. Functional ability refers to those capabilities that enable people to move around, build and maintain relationships, meet their basic needs, make decisions, and contribute to society. Functional ability comprises intrinsic capacity, environmental characteristics, and the interaction between them. This definition emphasizes that health at older ages is not just about maintaining physical and mental health but is also about creating an environment that enables older adults to live their lives to the full. In addition, given that health inequities persist into older ages, a meaningful public health response to population ageing must tackle the broader determinants of health.

Evidence from population-based cohort studies is vital to understand how these factors act across the life-course to influence healthy ageing and its trajectories. Over recent decades, many ageing cohort studies have been established globally. Yet, the availability of longitudinal data with a rich set of measurements in the context of healthy ageing as defined by WHO remains unclear.

Data collections

We identified ageing cohort studies across the globe through a holistic search strategy and following specific inclusion and exclusion criteria. Through our search strategy, we found 287 cohort studies worldwide. We extracted data on key characteristics of the cohort studies, including region, country, the aim of the cohort studies, sample size, age distribution at baseline, study duration, and the number of follow-up waves. Focusing on the WHO definition of healthy ageing, we also extracted data availability on demographics, socioeconomic circumstances, and environmental factors and the different healthy ageing domains measured in each cohort study.

Strengths and Limitations

Strengths

Using a comprehensive and multifaceted strategy to identify all ageing cohort studies across the globe;
Assessing multiple sources to collect relevant information for each cohort study;
Including a range of indicators for each intrinsic capacity domain as well as some measures of health characteristics (e.g., diseases, disability, and injuries).

Limitations

To find ageing cohorts, we searched various resources, including Online cohort directories and repositories, publications and consortium papers containing systematic reviews and harmonized cohort studies, and keyword searches on electronic journal databases, including key Epidemiology journals, which publish “cohort profile” articles. Despite having multiple strategies to identify relevant cohort studies, it is possible that not all eligible cohort studies were identified. To address this issue, principal investigators of relevant ageing studies that we were unable to identify will be able to contact us and provide information, which will then be added to the Toolkit database.
Data gathered on characteristics, demographic, socioeconomic, social and environmental, and intrinsic capacity measures were mainly based on information provided in cohort studies websites and published cohort profiles. Overall, we found gathering detailed information on variables measured in the cohort studies challenging mainly due to limited information available on data collection and limited access to study questionnaires. Through the Toolkit webpage, we welcome principal investigators to contact us and provide additional information related to their measurements.