he Nairobi DSS is part of the International Network of Field Sites with Continuous Demographic Evaluation of Populations and their Health in Developing Countries (INDEPTH). The INDEPTH Network aims to overcome a major constraint to the development of health polices and programs — a lack of accurate information. In much of the developing world, the registration of vital statistics is minimal or non-existent. Moreover, conventional sources of information — data collected from health care facilities — provide an incomplete picture of health problems. In Africa, where an estimated 80 % of people die outside of such facilities, millions of births and deaths go uncounted.
"There are models for population growth — but if you're going to make decisions, you have to do it on the basis of good data," says Dr Wendy Ewart, who directs a research funding program at The Wellcome Trust in London, England on the health consequences of population change. "We have to understand how society is changing."
A new book published by Canada's International Development Research Centre (IDRC) will contribute to this understanding. Population and Health in Developing Countries: Vol 1. Population, Health, and Survival at INDEPTH Sites summarizes mortality data and trends recorded at 22 INDEPTH research sites and reports on mortality patterns for Africa. The data is drawn from the sites' demographic surveillance systems (DSS).
A DSS is a way to continuously monitor populations at the household level within a geographically defined area. It records births, deaths, causes of death, and migrations in and out of the area. In the Nairobi DSS, for example, enumerators visit the same households every three months and gather information through interviews. In the slums, where makeshift houses can disappear overnight, this can pose some particular challenges. "The good thing is that the DSS is set up to deal with how people move. We track down all those movements," says Dr Pierre Ngom, a senior research scientist with the Nairobi DSS. Keeping track of who is moving where is important for the accuracy of the data — an individual should not be counted twice. The verbal autopsy is another innovative feature associated with many surveillance systems. When a death is reported, an interview is done with a close associate of the deceased. The interviewer asks about the symptoms, signs, and circumstances leading up to the death. The answers usually point to a cause of death.
The rich data that results from these and other techniques of demographic surveillance can help assess health problems, guide the selection of appropriate interventions, and measure their effectiveness.
Growth of surveillance
The first DSS was developed in Matlab, Bangladesh in 1966, a part of the field research program for the International Centre for Diarrhoeal Disease Research. At the outset, traditional birth attendants reported population changes in 132 villages on a weekly basis. Today, trained community health workers monitor more than 200,000 people in what has become the longest running surveillance system in the world. The Matlab DSS was instrumental in helping to prove the effectiveness of oral rehydration solution in preventing infant deaths due to diarrhea, a discovery that is credited with saving an estimated one million children each year.
In the last decade, other research sites in the developing world have incorporated similar surveillance systems into their work. (The availability and lower cost of computer equipment have helped boost DSS use.) Three of the sites have been part of IDRC-supported projects. In 1993, Ghana's Navrongo Health Research Centre built on previous surveillance resources to create the first DSS using a custom designed system created for Africa. It was used successfully in the field trials for insecticide-treated bednets in Ghana as well as in Burkina Faso, the Gambia, and Kenya. These trials showed that sleeping under nets reduced total child deaths by 17%.
South to south collaboration
Researchers from Navrongo helped to establish the Rufiji DSS, one of two sites that feed research data to the IDRC-supported Tanzania Essential Health Interventions Project (TEHIP). These sentinel DSS sites are helping local health planners to select cost effective interventions that take aim at leading causes of death and disease. The more strategic allocation of scarce health care resources has literally saved lives. In Rufiji, for example, child mortality has fallen dramatically between 1999 and 2001.
These findings highlight the particular value of DSS data for donors, at a time when there is greater demand for resources to be spent efficiently and equitably. "From a funder's point of view, if you're going to use interventions to tackle health issues, you've got to measure whether they work or not," says Dr Ewart. "Demographic surveillance helps you do that."
Benefits of network
Dr Ewart, whose Wellcome Trust program funds several DSS sites, calls them a "global resource." This resource is being strengthened through the INDEPTH Network, which brings together 29 DSS sites in Asia and Africa. Formed in 1998, the network serves to enhance the research capacities of the sites and their ability to coordinate activities and define the research and development agenda.
Dr Fred Binka, INDEPTH's Executive Director, administers the network from a secretariat based in Accra, Ghana. He points to Population and Health in Developing Countries as an example of INDEPTH's capabilities. "The monograph speaks for itself," says Dr Binka. "It's the information from all the sites that really makes the case for the contributions we can make over and above the country-specific sites."
For example, demographers and planners currently use statistical and demographic models for sub-Saharan Africa that are not based on actual data. "In the past, much of what we 'knew' about mortality in Africa was based on assumptions," says Dr Don de Savigny, research manager of TEHIP and a member of INDEPTH's Board of Trustees. Population and Health in Developing Countries challenges these assumptions by using real data from DSS sites to analyse mortality in Africa. The results show trends that differ from those mapped by the conventional models. In particular, the INDEPTH data describes more accurately the effects of HIV/AIDS on mortality — information that is of vital importance to efforts to deal with the pandemic.
INDEPTH plans to share its data and provocative analysis more widely through the publication of other monographs. These will cover new life tables for Africa, fertility trends, migration patterns, reproductive health, causes of mortality, and health equity.
Jennifer Pepall, a writer in IDRC's Communications Division in Ottawa, recently traveled to East Africa.