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Site description

Physical geography of the Dar es Salaam DSA

The Dar es Salaam region, on the east coast of Tanzania, includes the municipalities of Ilala, Temeke, and Kinondoni (which constitute the city of Dar es Salaam) and a few outlying areas (Figure 9.1). It borders on the Indian Ocean to the east and, on all other sides, the coast region. In 1988, the estimated population of Dar es Salaam, according to a national census, was 1 360 865. But the city grew rapidly during the 1990s, and the current population of Dar es Salaam is estimated at 3 million. The area participating in surveillance covered eight “branches” in two municipal areas of Dar es Salaam: Temeke and Ilala.

Dar es Salaam is at sea level, and the DSS site lies between latitudes 6.82° and 6.89°S and longitudes 39.24° and 39.30°E. The climate is typically tropical, with hot weather throughout the year (range, about 26°–35°C) and two rainy seasons: short rains in November–December and long rains in March–May.

¹ Adult Morbidity and Mortality Project, Tanzania.

Population characteristics of the Dar es Salaam DSA

Because socioeconomic status is important in the study of mortality differentials, three areas of the city — Ilala, Mtoni, and Keko — were chosen. These areas were thought best for the following reasons:

• Ilala, because it is an old planned part of the city, whose inhabitants are largely urbanized;
• Keko, because it is mixed socioeconomically, containing both people of higher socioeconomic status and government civil servants, living in reasonable accommodation; and
• Mtoni, because it is an area of fairly low socioeconomic status, whose citizens include a large proportion of the original inhabitants of the Dar es Salaam region, many leading a peri-urban or semirural life.

These three areas contain eight branches, with a total population of 69 304 (as of June 1999).

Originally, the Zaramo ethnic group inhabited the area that is now Dar es Salaam. During the 20th century, however, the population became a mix of many of the country’s ethnic groups. Thus, the population in the DSA is a mixture of people from all parts of Tanzania. The majority of the population in the project area are Muslims (70%), and the remainder are Christians (30%).

The major language of people participating in the DSS is Kiswahili. A large portion of people in the DSA engage in small business or manual labour (both skilled and unskilled); and a few have office jobs.

Information on the highest level of education attained by individuals has been collected in both the census and the mortality-data survey, and the proportion of girls attending school is slightly higher than that of boys for all ages up to 14 years. Thereafter, this proportion drops significantly. From age 25, women with no formal education constitute a proportion two to three times greater than that of men. From age 30, significantly more men than women have completed primary and postprimary education.

The majority of people in Dar es Salaam live in low-cost rental housing, and the mean household size is 3.8. More than 70% of households occupy only one or two rooms. About 80% of households have tap water. Use of pit latrines is extensive (90%) in the Dar es Salaam DSA. It has both paved and unpaved roads, and all areas are well served with public transportation. The area has both public and private telecommunications. Electricity is available in these areas, mostly for domestic uses, such as lighting and cooking.

The Dar es Salaam region has one national and three municipal-government hospitals. People in the surveillance area make good use of all these facilities, although none is within the DSA itself. Two of the municipal hospitals, however, are within easy access to the study community, and the DSS population also has access to government health centres and dispensaries and to a number of private hospitals and dispensaries. The private hospitals are outside of the DSA, but some private dispensaries operate within the area.

Dar es Salaam DSS procedures

Introduction to the Dar es Salaam DSS site

DSS work is carried out in Dar es Salaam primarily to provide reliable population denominators for continuous cause-specific mortality monitoring. The demographic and mortality monitoring together provide municipal authorities with information on the burden of disease, health-facility use in the period before death, and population conditions. These data are used for evidence-based planning and evaluation of health services. The monitoring is an activity of the Tanzanian Ministry of Health and the municipal health-management team, as part of the Adult Morbidity and Mortality Project, phase 2 (AMMP-2). The goal of AMMP-2 is to decrease the morbidity and mortality stemming from conditions particularly likely to cause suffering and disadvantage among Tanzania’s poor people, where these conditions are amenable to health-service interventions. To contribute to this goal, the project has aimed to strengthen evidence-based planning and development of cost-effective health services within the context of health-sector reform in project districts and in the Ministry of Health of Tanzania.

Demographic and mortality monitoring in AMMP-1 and -2 is carried out in Hai District (Kilimanjaro region) and Morogoro District (Morogoro region), as well as in Dar es Salaam (see Chapters 10 and 12). In 1992, when DSS work began, the Dar es Salaam DSA comprised seven urban branches, with a total population of 67 000. At the end of 1993, one more branch, with a population of 4500, was included in the monitoring to make a total population of 71 500. The population in the Dar es Salaam DSA has remained remarkably constant, despite considerable in- and out-migration each year. Although the initial focus was on adults, the system has been collecting data on people of all ages.

The DSS is incorporated into both national and district structures. In the Ministry of Health, the National Sentinel System assumes overall responsibility for using DSS to gather demographic and mortality data. This system also operates in the Hai, Morogoro, and Rufiji DSS sites. At the district level, surveillance work will become part of the routine systems of the district. Mortality monitoring will continue indefinitely, and DSS will continue as long as the district has no cost-effective alternative way of generating reliable population denominators.

The Dar es Salaam Public Health Service Delivery System is the primary local user of the data, and the Ministry of Health is the primary national user. Additional users of the data include

• The government’s multisectoral National AIDS Control Programme;
• The Vice President’s Office (which produces national poverty- and welfare-monitoring indicators);
• Ministry of Health initiatives for malaria control (for example, social marketing of insecticide-treated nets and the national malarial-drug policy);
• Nongovernmental organizations (for example, the Tanzania Public Health Association);
• Projects (for example, Dar es Salaam Urban Health Project);
• Donors (for assessment of health-sector performance);
• National Poverty Monitoring Group;
• Other sectors, such as the Ministry of Education, Bureau of Statistics, and Ministry of Labour and Youth Development; and
• Tanzanian and international researchers.

Dar es Salaam DSS data collection and processing

The initial population in the DSS approached the level that Hayes et al. (1989) suggested is best for the ascertainment of cause-specific mortality. As stated above, the Dar es Salaam areas were chosen to represent a range of urban living conditions, including variations in socioeconomic status and population density.

Field procedures

INITIAL CENSUS — An initial census was carried out in 1992, because neither vital registration nor the 1988 National Census provided an accurate basis for estimating population denominators. At first, a baseline census was taken to determine who was resident in each household under surveillance. A single form was used for each household.

REGULAR UPDATE ROUNDS — Subsequently, the population has been enumerated twice a year (May–June and October–November). In each update round, the information from the previous round is printed on new forms for each household. Each household is visited, and an adult member is interviewed. The enumerators verify and, where necessary, update existing data. When new households appear as a result of either migration into the area or splitting of existing households, they are registered on new-household forms. Key informants, such as local leaders, identify these households. Vital events (births and deaths) and migrations are recorded for each household. The following information is recorded for each individual: name, age, sex, relationship to head of household, main occupation, marital status, alcohol consumption and smoking habits, date of entry into the household, mode of entry, date of exit, mode of exit, and whether the individual’s parents are alive. Recently, questions on religion have been added. Migration tracking is limited to recording the dates of entry into and exit from the area and the district of origin or destination; successive migrations of individuals into and out of the area are not linked. Thus, although it is possible to determine who is resident at any point in time (and therefore to calculate denominators), it is impossible to calculate the total time particular individuals spend in the DSA.

The DSS employs eight community-development workers as enumerators for the census-update rounds, and three clinical officers act as verbal-autopsy (VA) supervisors. The system also has community-based key informants, who report deaths to the VA supervisor on a regular basis. Whereas the census-update rounds take place twice annually, mortality monitoring, which provides information on probable causes of death, is continuous. Probable causes of death are determined using VA techniques.

CONTINUOUS MORTALITY SURVEILLANCE — The primary objective of the AMMP approach to DSS is to provide sentinel data on the burden of disease to inform health planning and priority-setting, and thus efforts are made to determine the cause of death for each person who dies in the area under surveillance. This is achieved by interviewing the relatives and caretakers of the deceased, using a short, standard interview schedule. Different forms are used for deaths among infants <31 days old, children between 31 days and <5 years old, and all persons =5 years old. The forms contain a section to identify the respondent, one to identify the deceased, an open-ended history section, a checklist of previously diagnosed conditions, a checklist of symptoms and their duration, a list of health services sought in the period leading up to the death, a residential history, and a summary of any confirmatory evidence, such as medical records or a death certificate. Trained health personnel complete the form after interviewing one or more of the deceased’s relatives or caretakers. Wherever possible, the interview takes place within 6 weeks of the death.

Deaths are usually reported by community-based key informants, and in Dar es Salaam various individuals are used for this purpose. Key informants are chosen because of their awareness of events, such as deaths, in their communities. In addition, communities receive feedback in a newsletter; consequently, they perceive a benefit in participating in the surveillance system and actively report deaths to the key informants, thus making this a form of vital registration. Recently, each key informant from a village or area has been given a turubai (canvas tarpaulin) so that the bereaved families from the community can borrow it for funeral gatherings during the mourning period. This has enabled key informants to get information on a death that has occurred in his or her area and thus report it to the supervisor. The VA personnel meet the key informants on a regular basis to find out about new deaths that have occurred. They then meet with the relatives or caretaker of the deceased to verify that the death has occurred, then perform the VA.

Two physicians independently assign a cause of death. Until 1999, a modified version of ICD-10 was used. From 2000, a shorter, broader list of codes, developed by AMMP and the Ministry of Health, has been used. The diagnoses given by the two coders are compared, and discrepancies are given to a third coder. If all three coders disagree, the form is coded as “uncertain/unknown.” Wherever possible, confirmatory evidence of the cause of death is obtained. This includes in- and out-patient records, death certificates, and burial permits.

Data management

During the census, a field supervisor reviews all completed forms and returns those with errors and inconsistencies to the enumerators for correction. Those passing inspection are sent to the data centre in Dar es Salaam and entered into a computer. All census forms with errors detected during data entry are logged and returned to the field for correction. Once the corrected forms are returned to the office, they are logged back in, and the problems are resolved.

Staff are trained to enter the data into microcomputers using a data-entry system designed specifically for the project in Microsoft FoxPro. They are instructed on how the census forms should be completed so that, in addition to the computer validation programs, they, too, can detect errors and inconsistencies. The validation programs range from simple range checks to checks for inconsistencies across household

members, such as an individual identified as a “spouse” but with marital status recorded as “never married.”

Several methods are employed to ensure data quality, including checks in the field and in the data-entry process. Supervisors visit a random sample of households to verify entries on the census forms and check that the census includes all the households visited and that no nonexistent households have been included. Following each census, reinterviews are also conducted of a sample of households for each enumerator. Because of the large amount of data collected in a single census, it is impossible to double enter all data for verification; instead, a 5–10% random sample is taken, and the forms are checked against the entered data.

At the end of each interview, the interviewers give each household a newsletter designed by the municipal health-management team and produced and distributed by the project for US $0.11 per household. It contains health-education messages and simplified presentations of results from the previous round. It shows that the DSS is part of the functioning of the district health system. The newsletter is designed to help the communities and their leaders better understand the areas where they live. In 1999, 94% of households reported receiving the newsletter, and 89% of households reported reading it.

Dar es Salaam DSS basic outputs

Demographic indicators

The primary outputs of the system are estimates of cause-specific mortality for all ages. As stated, the resident population of the DSS site is about 70 000. Average household size is 3.8. Male–female ratio is 100 : 102, with an age-dependency ratio of 59%. The main age group structures of the current population are as follows: those <1 year old account for 3.1%; 1–4 years old, 10.4%; 5–14 years old, 21.9%; 15–64 years old, 63.0%; and =65 years old, 1.6%. Between July 1992 and June 1999, the maternal mortality ratio was 669 per 100 000 live births.

The following migration figures reflect changes of residence of people on an annual basis and do not capture short-term movements between the enumeration rounds. In 1998–99, the surveillance area had an out-migration of 17 796 people. The region of destination was obtained for 15 124 of these: most (75%) migrated to another part of Dar es Salaam; the rest, to various parts of the country, except for 172 who moved to other countries outside Tanzania. During the same years, 16 581 people migrated to households within the surveillance area. The place of origin for 13 087 (79%) was determined: 68% migrated from areas within Dar es Salaam; the remainder came from other parts of Tanzania, except for 67 who came from other countries. As can be seen from the figures above, the population in the Dar es Salaam surveillance area is very dynamic. Dar es Salaam attracts young adults, and this can be seen in the shape of the population pyramid (Figure 9.2). The excess of females becomes obvious in the 15–19-year age group, whereas for males this occurs 5 years later.

Table 9.1 shows the age- and sex-specific all-cause mortality at the Dar es Salaam DSS site.

In 2000, AMMP added questions to the census round to determine more detailed fertility and migration characteristics and their effects on the population structure. Preliminary analyses of the data indicated that a considerable amount of short-term migration occurred between census rounds. In addition, the age-specific fertility rates of those who migrated to Dar es Salaam were about half those of older residents. The in-migration of young adults, with lower levels of fertility, contributed to the “bulge” in the population pyramid in the 15–49 age group. These are preliminary data, and further analyses of these data are planned.

Acknowledgments

AMMP is a project of the Tanzania Ministry of Health, funded by the Department for International Development (DFID), United Kingdom. The project is implemented in partnership with the University of Newcastle upon Tyne, United Kingdom.

This chapter is, in part, an output of a project that DFID has funded for the benefit of Tanzania and other developing countries, and the views expressed are not necessarily those of DFID.

The AMMP team includes K.G.M.M. Alberti, Richard Amaro, Yusuf Hemed, Berlina Job, Gregory Kabadi, Judith Kahama, Joel Kalula, Ayoub Kibao, John Kissima, Henry Kitange, Regina Kutaga, Mary Lewanga, Frederic Macha, Haroun Machibya, Honorati Masanja, Louisa Masayanyika, Mkamba Mashombo, Godwill Massawe, Gabriel Masuki, Ali Mhina, Veronica Mkusa, Ades Moshy, Hamisi Mponezya, Robert Mswia, Deo Mtasiwa, Ferdinand Mugusi, Samuel Ngatunga, Mkay Nguluma, Peter Nkulila, Seif Rashid, J.J. Rubona, Asha Sankole, Daudi Simba, Philip Setel, Nigel Unwin, and David Whiting.

The AMMP team would like to acknowledge the municipal health-management team from Temeke and Ilala for their continued support and collaboration. We are also grateful for the contributions and efforts of AMMP support staff: Mariana Lugemwa, Dorothy Lyimo, Rukia Mwamtemi, Getrude Peter, Charles William, Mustapha Kahise, and Juma Mfinanga. Finally, we would like to express our sincere thanks to all those who live in the project area for their patience and cooperation.

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