Founding Documents

The problem

 As the year two thousand approaches, with the revolution of the information age still gaining speed, it seems inconceivable that for large parts of the globe's population there remains a void in vital health information. For one billion people living in the world's poorest countries, where the burden of disease is highest, those who are born or who die are still not counted. From the limited data available, the health profile of these populations is akin to an iceberg: the bulk of reliable data on trends in age, gender and geographic variations remains to be uncovered. This great void in population-based information constitutes a major and long-standing constraint to the articulation of effective policies and programs aimed at improving the health of the poor and as such perpetuate profound inequities in the health of the poor.

The imperative for a reliable information base to support health development has never been greater. Although cost-effective interventions exist for the unfinished agenda represented by high mortality and fertility rates, their potential benefit has yet to be realized. Without population-based data, health services rarely reach those at greatest risk, most of who die without any contact with the health system. At the same time, high mortality societies contain a growing population whose health profile reflects surprisingly high rates of chronic diseases. There is a similar inability to reliably document the health status of this population, and virtually no capacity to assess potential interventions. Of particular concern is the greater interface of this population with the health system, which may skew allocations away from the high mortality conditions. Moreover, dynamic global forces are leading to a third wave of health threats which include violent deaths, accidents, mental illness and new infectious pathogens, for which reliable systems of ongoing monitoring and surveillance are wanting. Finally, priority policies directed to the problems of high fertility and reproductive ill-health remain unimplemented as they are inadequately guided by evidence and trial.

Available Sources of Data

 Ironically, there is a surprising amount of information-generation, research activity, and capacity in data-poor countries. This reflects the ever-growing demand for information on which to base decisions. These efforts, however, are plagued by poor coordination and communication, inadequate standardization of methods, excessive quantities of misleading or poor quality data, fragmentary and biased coverage in existing information systems, and missing links with policy and program. Furthermore, current health information systems are expensive, facility based, divert limited research expertise, fail to develop institutional or individual capacities, and because they do not reflect the problems of people in their communities provide no systematic approach for planning the allocation of health resources.

 Standing in sharp contrast, however, is the experience of a limited number of field stations which have, as their foundation, continuous monitoring systems of geographically defined populations that can generate high quality, population-based, health and demographic data on a longitudinal basis. These field sites have a proven track-record in providing high quality population-based information often operating in highly disadvantaged environments. These data are able to inform, on the one hand, priority setting, policy decisions and the allocation of resources and, on the other, a highly-focused, intervention-oriented, research agenda. They constitute a critical yet weakly harnessed alternative to the dearth of valid, population-based information in much of the developing world. Moreover, the fast-paced development of user-friendly computer technology, accompanied by sharp reductions in cost, has greatly reduced the financial and technical obstacles to establishing such sites.

The Potential of Demographic Surveillance

 The methods, approaches and work settings offered by field sites supporting continuous monitoring of vital events in geographically defined populations provide unique opportunities. These relate to the methodological strength of longitudinal follow-up of defined populations, the findings that can result, and their applications to health and other social systems.

 A profile of cause-specific mortality for an entire population can make a critical contribution towards strengthening the information base on which to rest decisions about health care practice. This is of fundamental importance given the widespread health reforms underway. Decisions include: targeting priority diseases and health conditions, allocating scarce financial and human resources, improving the efficiency of programs, and developing the skill-base of health workers.

 A demographic surveillance system (DSS) provides a platform on which to base a range of health, social, economic and behavioral studies. These can take advantage of the sampling frame inherent in a DSS, whether at individual, household/compound or neighborhood level. Studies may be inter-linked, exploit a mix of qualitative and quantitative methodologies, and address a diversity of formative, hypothesis generating, or hypothesis driven issues. Findings can be related to underlying patterns of mortality, fertility and migration. There is thus the potential for significant research efficiencies when work is super-imposed on a well-functioning surveillance system.

The impact of interventions on mortality, non-fatal health outcomes, fertility and migration can be rigorously assessed. Interventions may be therapeutic (such as new drugs or vaccines), behavioral (e.g. sexual and reproductive behaviors) or involve changes to routine service delivery, health policy, or more extensive health reforms and development strategies. They may address the maximum impact of interventions under strictly controlled conditions (efficacy), or the impact of introducing new interventions into already existing services (community effectiveness). In a number of cases, such as bed-nets, vitamin A supplementation and measles vaccine trials, unexpected health gains/losses have been revealed by the ability to track overall and cause-specific changes in mortality.

Methodologically, the prospective study design is immensely powerful as it links a sequence of events (births, migration in or out, disease, death) to the life-course of a particular individual. This imparts great power to the search for the primary causes of severe ill-health. Grounding the work in a whole population sample removes many of the biases that characterize other study designs.

 Long-term engagement with poor, often marginalized communities provides the opportunity for in-depth understanding of their priority concerns and pressing health needs, their health care preferences and responses to service innovation, and individual and group reactions to social change.

 Finally, these research environments provide unparalleled applied training opportunities for health and other professionals, with a particular emphasis on strengthening national capacities to seek, interpret and apply available information in the essential effort of evidence-based policy, practice and resource allocations.  Read more