Foreword: The INDEPTH WHO-SAGE collaboration – coming of age

I t is no surprise that there is a lack of evidence on the health of older populations in lowand middleincome countries. Much current attention is focused on the Millennium Development Goals, prioritising maternal and child health and leading infectious diseases. The epidemiological transition is relatively recent and health researchers and policy-makers are still grappling with the new data demands. And even in high-income countries, which face increasingly large older populations and predominance of chronic diseases, there are major evidence gaps. The set of papers in this Supplement represent a significant step towards better evidence on the health of older populations. The papers are based on studies in four African and four Asian countries as part of a collaboration between two multi-country networks. The first network is the well-established International Network for the Demographic Evaluation of Populations and Their Health (INDEPTH) in developing countries. It is an international platform of sentinel demographic sites that provides health and demographic data and research to enable developing countries to set health priorities and policies based on longitudinal evidence and includes more than 30 sites, mostly in Africa and Asia. It has an outstanding record of collecting vital statistics and has been a vehicle for the generation of information on a wide range of health topics. The second network is the World Health Organization (WHO) Study on Global AGEing and Adult Health (SAGE). SAGE is a multi-country study that addresses health and health-related outcomes and their determinants in populations around the world with a focus on lowand middle-income countries. The emphasis is on common methodological approaches to ensure cross-population comparability. SAGE country studies aim for a longitudinal cohort design with the inclusion of populations 50 years and over along with a comparative cohort of persons aged 18 49 years. The first round has recently been completed in China, Ghana, India, Mexico, Russia and South Africa. The SAGE and INDEPTH networks have initiated a collaboration to study adult health and ageing in lowand middle-income settings. This collaboration offers several unique features which will allow both the generation of unique evidence and detailed methodological work to validate self-reported morbidity and survey mortality data. INDEPTH sites have relatively large populations under surveillance with regular monitoring of vital events, which allows the inclusion of a standard short module to examine health and health-related outcomes in regular surveillance rounds. In addition, innovative strategies can be developed to link survey and surveillance data to inform larger national estimates as well as developing and testing strategies for robust small area estimates. In three of the eight countries with sites Ghana, India and South Africa reported in this volume of Global Health Action (GHA), national SAGE studies are ongoing. The collaboration will also draw upon the expertise within INDEPTH sites to improve methods in data collection in older populations in lowand middleincome countries. This includes improved recording of age, development of verbal autopsy tools to assess the cause of death in the ageing population, the measurement of health and health-related outcomes for ageing care providers caring for HIV/AIDS orphans, and the caregiving burden and its association with health. Other routinely collected demographic data such as migration and its relationship to health outcomes will also be essential. Furthermore, some sites have data from other studies on changing patterns in risk factors and can relate that to the health status of older adults. This Supplement to GHA brings together the first set of papers from this collaboration. This set of papers focuses on describing the current situation among older people and identifies a number of consistent patterns. For instance, the health of women among older adults is worse than that of men; living alone jeopardises health and wellbeing; and being poor is bad for health. There are, however, important differences within and between sites as well. For example, older adults in Vadu, India, who are not in a partnership are not as badly off as in other study sites, probably because of support from extended and adjoined families; older adults with the poorest health in Purworejo, Indonesia, are clustered in the semi-urban belt of the district; and patterns of the older adult population structure are changing as exemplified by the predominance of older men in Agincourt, South Africa and of older women in the slums of Nairobi, Kenya. The results also reveal close relationships between declining health, increasing disability and worsening of quality of life in the ageing population. FOREWORD INDEPTH WHO-SAGE Supplement