African Population Studies Vol 26, 2 (Nov 2012)

Setting up a Demographic Surveillance System in Northern Angola

Maria João Costa *,1 Edite Rosário*,1António Langa, 1Gaspar António, 2Ali Bendriss 1,3 and Susana Vaz Nery 1a) 1 CISA Project (Health Research Centre in Angola), Caxito, Bengo, Angola; 2 Universidade Agostinho Neto, Angola; 3 Université Paris 8

a Corresponding author: CISA Project, Centro de Investigação em Saúde em Angola. Hospital Provincial do Bengo, Rua Direita, Caxito. Angola Tel. +244 921782840; [email protected] * The authors contributed equally to the work.

Abstract As in many regions of the developing world, the lack of accurate and up to date demographic information in Angola is a handicap to demographic and health research. To overcome this gap, a Health and Demographic Surveillance System (HDSS) was designed to support the research activities of CISA Project, a health research centre created in 2007 and located within Dande municipality in north- ern Angola. Here we report the methodology for setting up the HDSS-Dande as well as the adjustments made to improve the data collection process since the conclusion of the baseline census in April 2010. The HDSS data is instrumental for the support of epidemiological and other health studies.

Resumé Comme dans de nombreuses régions du monde en développement, en Angola le manque d'informations démographiques exactes et à jour est un handicap pour la recherché démographique et de santé. Pour surmonter cette lacune un système de surveillance démographique et de santé (SSDS) a été conçu pour soutenir les activités de recherche de CISA Project, qui est un centre de recherche médicale, créé en 2007 et situé dans la municipalité du Dande, dans le nord del'Angola. Nous rapportons ici la méthodologie choisie pour la mise en place de la SSDS- Dande ainsi que les ajustements effectués pour améliorer le processos de collecte des données depuis le recensement de base conclu en avril 2010. Les données du SSDS sont instrumentales pour le soutien des études épidémiologiques et d'autres études de santé.

Keywords: Angola, health and demographic surveillance system, HDSS, longitudinal data, health research

Introduction a partnership between Angola and Por- With the overall goal of contributing to tugal was established in 2007, to create the improvement of health conditions a health research centre,“Projecto in Angola through training and research, CISA” (Centro de Investigação em Saúde em Angola).1 The CISA Project is http://aps.journals.ac.za 133 African Population Studies Vol 26, 2 (Nov 2012) located within the Bengo General Hos- The DSA (Figure 1) covers the pital, in Caxito, a city 60 km northeast communes of Caxito, Mabubas and of Luanda, in the Municipality of Dande, Úcua, a contiguous area with a total Province of Bengo.2 area of 4.763,6 km2. The climate is CISA Project´s research interests tropical dry with an average tempera- include observational, intervention and ture of 25ºC. The annual precipitation clinical studies in malaria, tropical is low on average (600 mm), although neglected diseases (schistossomiasis, rainfall can be strong and destructive soil transmitted helminthiasis, tripanos- and drought is a problem both for agri- somiasis), and other diseases with pub- culture and water supply (Tavares and lic health relevance in the area. In 2008 Arsénio 2007). Three rivers cross the a Health and Demographic Surveillance DSA and nine lakes are located within System (HDSS) was designed and the area. Man-made irrigation channels implemented to support these research exist within Caxito and Mabubas. Two activities. The main objective of the main interprovincial paved roads cross HDSS is to collect accurate longitudinal the DSA, all others being dirt roads, data on population structure, dynamics making it difficult to reach some of the and location, providing reliable up-to- rural communities during the rainy sea- date denominators for the calculation of son. Health problems have been mainly vital rates and analyses requiring ‘at risk’ associated with infectious diseases, populations, as well as to provide a especially malaria (WHO 2011, AMD sampling frame for epidemiological or 2006), which is commonly referred to as a major cause of death. Other infec- other health related studies. tious diseases present in the area This paper describes the methodol- include sleeping sickness and schis- ogy used for setting up the HDSS- tossomiasis. Dande, the design and implementation Of the 69 hamlets which comprise of the field and data management pro- the DSA, 26 are in urban areas (25 cedures, the difficulties and limitations hamlets in Caxito, the capital of Bengo’s of collecting, storing and producing Province, and one in Mabubas).3 information, and the efforts to over- come these difficulties and limitations. It also includes a basic demographic description of the people living in the surveillance area, as well of their hous- ing conditions.

1. CISA Project is the first Health Research Centre in Angola. It is the result of a partnership between the Portuguese Institute for Development Assistance (IPAD), Calouste Gulbenkian Foundation (FCG), the Angolan Ministry of Health (MINSA) and the Bengo Provincial Government and is being developed under the scope of the Cooperation Program between Angola and Portugal. 2. The major administrative areas in Angola are the Provinces (“províncias”), which are divided into municipalities (“municípios”), which in turn are divided in communes (“comunas”). Within the communes, the population lives in hamlets (“bairros”). Hamlets designate the group of houses that comprise villages in rural areas and neighborhoods in urban areas. http://aps.journals.ac.za 134 African Population Studies Vol 26, 2 (Nov 2012)

The Demographic Surveillance Area (DSA)

Figure 1 Health and Demographic Surveillance Area in the Dande Municipality, Bengo Province, Angola

Literature review and health policies (Ngom 2001, Sié et al. theoretical framework 2010). The majority of the established HDSS are organised in the International A HDSS is the process of defining risk Network for the continuous Demo- and corresponding dynamics in demo- graphic Evaluation of Populations and graphic rates of birth, death and migra- their Health (INDEPTH). This network tion over time (Phillips 1998). It is an has 42 members in 19 countries, and important tool to address health and most of them are located in Africa (29) epidemiological studies and to inform and in Asia (12) (INDEPTH 2011).

3. Urban areas are defined as the capitals of provinces and municipal headquarters, having agglomerations of 2 000 or more inhabitants and basic infrastructures (schools, health centres, pavement main roads, etc.) (National Statistics Institute of Angola, 2011). Rural areas are mainly dispersed settlements. http://aps.journals.ac.za 135 African Population Studies Vol 26, 2 (Nov 2012)

None of the African centres is located lected at the individual (sex, date of in Angola nor in Central Africa, rein- birth, relationship to the head of house- forcing the importance of the imple- hold, literacy level, parents’ and hus- mentation of the HDSS in Dande within band’s identifications) and household the international health research pano- levels (composition of the household rama. walls and roofing materials, number of The general methodology of a rooms, source of drinking water, exist- HDSS consists in performing an initial ence of kitchen and latrines). census, i.e. enumerating and registering A resident in the HDSS-Dande is the entire population of a given geo- defined as any person who lives, has graphic area, followed by updates on been living or intends to stay in a house- demographic and health related events, hold for a period of at least three for every resident in the DSA, accord- months. People who live in more than ing to a specified and regular periodic- one household are registered where ity, therefore keeping a longitudinal they spend more than half their time. A cohort of life events (Sankoh 2002; person’s follow-up ends within the Clark 2004). Although the INDEPTH HDSS when he/she migrates to an area provides the basis for the standardiza- outside of the DSA (Hosegood 2007 tion of methodology (INDEPTH and Nhacolo et al. 2006). 2011b), each HDSS adopts its own, A household is defined as any group according the local context and its pur- of people living together and sharing pose. the same economy. Members of the Although same papers discuss the same family living in the same house but methodology for longitudinal monitor- having separate domestic expenses and ing systems, the published literature on identifying different household heads HDSS is mainly on demographic and count as two or more households. The health outcomes resulting from long- household head is the person recog- term sequential data collection (e.g. nized as such by the members of the Kamugisha et al. 2001, Adazu et al. household. Some persons are heads of 2005, Kahn et al. 2007, Jahn et al. more than one household but are regis- 2007). The current manuscript aims to tered as residents of only one. Polyga- fill that gap. mous men are registered in the house of the first wife. Data and methods A unique identifier system is used to The HDSS-Dande initial census was follow individuals longitudinally. Each conducted between September 2009 household is given a code in which the and April 2010 and since then each first three characters indicate the ham- household is visited every four months let and the last four the house number. to update information on pregnancies, This code is then used to create the births, deaths and migrations. individual permanent ID, based on the location where each person is living the Variables and concepts under first time he/she is identified by the sys- surveillance tem. When a person changes his/her During the initial census data were col- place of residence within the DSA, a http://aps.journals.ac.za 136 African Population Studies Vol 26, 2 (Nov 2012) location ID is registered, allowing the holds.5 Twenty one field workers database to keep record of all move- (sixteen interviewers and five supervi- ments, to track migrations and to avoid sors) and six data clerks were consid- double enumeration of members in the ered necessary for the implementation database (Kahn et al. 2007). of the baseline census. All workers underwent an initial two-week training Design and implementation of session and weekly meetings between procedures the entire field team and the HDSS The initial census work plan was pre- manager allowed for knowledge con- sented to all levels of local administra- solidation and problem solving. tion (municipality, communes and hamlets). The scouting operations in Counting, enumerating, and the field took place from May to georeferencing of households December 2008. Hamlet coordinators During the process of counting the and traditional authorities (‘sobas’) col- households of the area, done to pre- laborated with the HDSS team in the view the dimension of the census and process of recognising territory, helping to estimate logistic needs (such as the to define the borders of each hamlet household identification plates), it and mediating the contacts between became evident that the real number of the field team and the local population, households would fairly exceed the namely through the arrangement of estimates of the total population based community meetings. These meetings on the data of AMD. Therefore only were organized in each hamlet before three of the five communes of the the beginning of fieldwork with the pur- Dande municipality were included pose of informing the population about (Caxito, Mabubas and Úcua), to main- the HDSS’s objectives and mobilizing tain the initial intention of about 60,000 them to cooperate. people under surveillance. The three A pilot survey was done to test and communes included in the DSA are adjust the questionnaire. A manual with contiguous and comprise urban and all the definitions, procedures and staff rural settings, with a variety of land- functions was produced and distributed scapes and environmental conditions. to the entire team, along with the set of After counting, the households of forms used for data collection and qual- the DSA were enumerated, i.e. the- ity control. household ID code was painted on Team dimensioning was based on wooden plates and fixed at the main the productivity results of the pilot sur- entrance of each household, facilitating vey4 with the aim of setting up a HDSS its visibility by the household members covering approximately 60,000 people, and field workers. Given the impor- that according to the available data by tance of the geographical location of the Municipal Administration of Dande events for understanding health out- (AMD) would include the entire munic- comes (Montana and Spencer 2001), ipality and correspond to 14,000 house- the households were simultaneously

4. Each fieldworker interviewed an average of fifteen households per day. 5. Considering the average number of 5 inhabitants per household given by the Malaria Indicators Survey (MIS) 2006-2007 (COSEP, 2007). http://aps.journals.ac.za 137 African Population Studies Vol 26, 2 (Nov 2012) georeferenced, using a hand-held geo- the end of each round a period of revis- graphical positioning system (GPS) its is planned as a final attempt to inter- Garmin 60 Cx. Household georeferen- view a resident in all households. tiation was complemented with the col- Whenever an adult member is not avail- lection of coordinates of relevant able after all the revisits, a neighbour locations such as roads, paths, rivers, may serve as a proxy informant to col- lakes, irrigation channels and public lect basic information. The information buildings (health facilities, schools, that the respondent is a non member of administration, churches, etc.). All the the household is registered in the ques- coordinates were integrated in a geo- tionnaire. database and will be used to produce Data on housing conditions is maps. updated only once a year and was actu- alized at the end of 2011 during the 5th Initial census and update rounds round. The census which established the base- line population has been followed by Data management and quality update rounds in order to update the control information on demographic events for The field team reviews every question- every resident in the DSA and to keep a naire to check for missing answers and longitudinal data collection. Given the major inconsistencies. Supervisors are high mobility of the population in the responsible for additional procedures DSA update, rounds are carried out to guarantee the quality of data collec- every four months to minimize the loss tion, including: random spot checks of events such as deaths, births, abor- (duplication of 5% of the interviews to tions or stillbirths and in and out migra- assure the veracity and quality of field tions. With the support of a update work) and supervised visits with each round book, which summarizes all the fieldworker (to monitor their perform- collected individual data in each house- ance). hold, the field team visits each DSA At the Data Unit questionnaires are household, checks the composition of recorded and issued a unique ID serial the household and registers demo- number. Quality is assured by validation graphic events (who died, who was checks, double entries verified by auto- born, who entered or left the DSA and matic comparison and regular compu- when). In each household there is an ter checks to look for inconsistencies attempt to recruit an adult member (e.g. duplicated ID and members, capable of giving information on all the wrong ID on deaths and out-migration). residents and on the characteristics of Inconsistent or illogical data returns to the household. In the absence of such a the field for correction. suitable informant the field worker Daily copies of the database are schedules a new visit, with a maximum made, one of which is kept outside the of four visits per update round,6 and at computer room for safety.

6. The four revisits are done only in the hamlets with good accessibility. In some of the rural areas that are difficult to reach, the round plans only two visits (a regular visit and a second one at the final period of the round). http://aps.journals.ac.za 138 African Population Studies Vol 26, 2 (Nov 2012)

Ethical issues tacts are needed, by radio The HDSS forms were registered in the announcements or through super- National Institute of Statistics of Angola visor visits, in order to schedule (INEA). Participation of households, interviews according to the availa- both in census and update rounds, is bility of the population. Hamlet voluntary and verbal consent is coordinators are important liai- required. After the initial census sons with the population. researchers provided feedback infor- 2. To obtain accurate data on the char- mation to all levels of the administration acteristics of the members of the and promoted meetings with local lead- DSA: the difficulty of obtaining ers to discuss research findings, where accurate data in some African cen- fact sheets with the main demographic suses and surveys, with contexts findings of each hamlet and commune identical to those found in our DSA were distributed. All individual data was (high rates of illiteracy and lack of treated in confidentiality and no infor- identification documents) is well mation on names was disseminated. documented (United Nations 1955, To assure confidentiality of stored Andoh 1980; IDRC 2002; Jahn et al. data, password access and different lev- 2007; Adazu 2009). Sometimes els of access, depending on the user, is respondents find it difficult to guaranteed. answer questions related to other Health and social problems men- residents of the household and tioned by residents during their visits occasionally about themselves, were communicated to the Provincial mainly on names and ages. People Health Directorate and Social Services often use different names at differ- respectively. ent moments (one name at home Challenges and constraints in the and another at school, for example) follow-up of individuals in the and nicknames are common (peo- HDSS ple are frequently known as “the Specific procedures are in place to eldest one”, “the youngest one”, overcome the many difficulties arising “mummy”, “daddy”), making it dif- from following up all residents and ficult to register official names and event in the DSA, listed below. to guarantee that residents will be 1. To ensure a high coverage of the identified in the next visit. In order population: some geographically to minimize these problems the isolated populations, mostly coal field team should ask for documents burners and farmers, can be very to obtain dates of birth and names difficult to reach, as roads leading as accurately as possible or, in the to these locations may become absence of such documents or relia- inaccessible during the rainy sea- ble information, to use approximate son. Additionally, these workers dates when the respondent doesn’t are not available during the day, as know the exact year, month or day they leave their houses very early of his own or someone else’s date in the morning and return at night. of birth.7 In the last case, field For successful visits previous con- workers register that a date of birth http://aps.journals.ac.za 139 African Population Studies Vol 26, 2 (Nov 2012)

has been estimated and make a after the visit of the fieldworker and note to confirm the exact date in would be reported in the following the next visit. During the initial cen- round. Others might have been sus, 3% of the individual birth dates omitted due to cultural issues. To registered was estimated by the overcome these questions, field field workers. workers receive constant training, 3. To track migrants: people often namely during the weekly meetings move from one household to with several role play exercises, on another within the DSA. These techniques regarding how to movements correspond to internal approach interviewees in order to migrations. In order to prevent obtain reliable and complete infor- duplicate registries, complete inter- mation. Furthermore there has nal migration file reconciliation has been an effort to strengthen the been introduced, i.e. every in- network of community informants, migration register form of someone especially through systematic con- who moves within the DSA has to tacts with hamlet coordinators, match with its counterpart out- who are asked to register deaths migration register form. Reconcilia- and births in the hamlet. Another tion of in and out-migration forms is attempt to reduce the number of performed at the data manage- “missing deaths” is consulting hospi- ment unit, where computed opera- tal records. These records are then tions facilitate the detection of compared with the HDSS database double registers. to find correspondences between 4. To reduce missing demographic the names of people who died in events. The number of births the hospital and the residents in the expected in the DSA for one year, DSA. In order to avoid losing peri- based on the age specific fertility natal deaths (due to an undercount rate given by the MIS (COSEP of stillbirths and early infant deaths 2007), is of 2.640 whereas the DSA that can occur between the captured 2.371 (90% of the rounds), each known pregnancy expected) in a similar period. and expected date of birth is regis- According to the World Health tered. The database produces lists Organization estimates for mortal- of expected births, helping to con- ity in Angola in 2009, the expected trol its data collection. number of deaths in the DSA in one year would be 1,115 whereas only Results 581 deaths were registered (52%). Some deaths may have occurred Demographic data and housing

7. Field workers have a calendar of local events to help respondents locate dates of birth and a table of conversion of calendar years in years of age and vice versa. Furthermore, there are defined rules to approximate dates when the day or month of birth is unknown: the interviewer tries to determine whether the person was born in the beginning, middle or at the end of the month (then indicating date of birth on days 5, 15 or 25). When the respondent does not know the day or the month of the birth date, the interviewer indicates the date as 30th of June (middle of the year). http://aps.journals.ac.za 140 African Population Studies Vol 26, 2 (Nov 2012)

conditions rural areas). The median of the distribu- The HDSS-Dande initial census regis- tion is 3 and the mode is 1 (in urban tered 15,643 households and 60,075 centres, median and mode are both 4, people. The population density in the and in rural areas more people live 2 DSA is 12.6 inhabitants per km . Urban alone, being the median and the mode areas concentrate a great part of the of 2 and 1, respectively). population (70% of the households, The population age pyramid of corresponding to 77% of residents). HDSS-Dande (Fig. 2) illustrates the pre- The average number of inhabitants per household is 3.8 (4.2 in urban centres dominance of young and the reduced and 3 in rural areas), which is influenced number of aged people (half the popu- by the large number of households lations is under 20 years old, 46% have composed of singular persons (19% of ages between 20 and 64 years old and total, 10% residing in urban and 9% in only 4% are 65 or over).

[85, +’[ [80, 84] [75, 79] [70, 74] [65, 69] [60, 64] [55, 59] [50, 54] [45, 49]

[40, 44] Male

Age GroupsAge [35, 39] Female [30, 34] [25, 29] [20, 24] [15, 19] [10, 14] [5, 9] [0, 5[

5.000 3.000 1.000 1.000 3.000 5.000

Population

Figure 2 Population pyramid of HDSS-Dande, 2010

The median age within the HDSS- siderably according to the place of resi- Dande is 19 years old, 18 in urban and dence, being the urban population 29 in rural populations. Those values, as younger than the rural (54% and 40% well the different age ratios (Table 1), under 20, respectively). People aged 65 show that the age structure differs con- or above represent 3% of the total http://aps.journals.ac.za 141 African Population Studies Vol 26, 2 (Nov 2012) population in urban areas and 7% in measures the relation between the two rural areas. halves of the female population in The indicators of fertility also show reproductive age shows that the poten- different patterns according to the tial for fertility, defined as the number place of residence. Women of child- of women aged 20-34 per 100 women bearing age represent 48% of the aged 35-49, is much higher in urban female population in urban centres and (237) than in rural areas (89). 40% in rural areas. The ratio that

Table 1 Demographic ratios calculated for DSA, according to rural-urban residence Ratios DSA Urban Rural Youth ratio (under 15/over 64)*100 11,4 16,7 5,0 Ratio of children (aged 0-4)/(aged 5-9)*100 100 100 100 Age dependency ratio (under 15+over64)/(aged 15-64)*100 80 85 65 Youth dependency ratio (under 15)/(aged 15-64)*100 74 80 54 Elderly dependency ratio (over 64)/(aged 15-64)*100 6 5 10 Child-women ratio (0-4)/(women aged 15-49)*1000 650 656 627 Ratio of (women 20-34)/(women 35-49)*100 189 237 89 Sex ratio (man)/(women)*100 98 96 102

The most common referred wall mate- Index (WI), the Myers’ blended Index rial in the DSA was adobe, whereas iron (MI) and the United Nations Age-Sex sheets were the predominant roof Accuracy Index (ASAI). According to material. The majority of households the WI and MI, the census results are (70%) do not have a kitchen and almost reliable data (WI = 95, MI = 4.2), and half the households (45%) do not have according to the ASAI are fairly reliable latrines. Of those that have latrines data (ASAI = 38.7). 43% share them with neighbours. More than half households in the HDSS Discussion (62%) obtain drinking water from an unimproved source: 48% of the house- Regarding methodology and the proce- holds from a river, 10% from an unpro- dures followed in the HDSS-Dande, tected dug well and 3% from lakes and there are some aspects that need to be irrigation channels. Only around 8% of improved, namely the communication the households, located mainly in urban and the involvement of the community areas, have access to private taps of of the DSA. Occasionally field workers treated water. have difficulty attempting to interview people not used to door to door ques- The accuracy of data tionnaires and maybe because of the The accuracy of data collected was long war period in Angola they are not evaluated by standard statistical and very “open” to expose their identity, demographic methods: the Whipple’s especially those working in security or http://aps.journals.ac.za 142 African Population Studies Vol 26, 2 (Nov 2012) police forces (a considerable number of movements, making it difficult to com- adult men). To overcome this problem pare with the composition of greater it was necessary to organize meetings populations (e.g. Clark, 2004; Adazu et at the police headquarters to explain al., 2005). Despite these limitations, in the objectives of the HDSS. There is the absence of vital records or of also the constant need to deal with the demographic and health knowledge of expectations of the population, who specific populations, the DSA is an expect drug distribution or provision of important tool to support health health care services, since field workers research and interventions. In the par- are associated with a health research ticular case of CISA Project, the popula- centre. Another aspect to highlight is tion registered in the DSA (60,000) is the local understanding of the ID plates more than double the estimates given which enumerate the households. They by the local Administration of popula- had a very good acceptance by the tion for the three communes under sur- inhabitants of the DSA and are being veillance (29,000 persons) (AMD 2006). used for other purposes such as in resi- This lack of knowledge on the demo- dential addresses and by the electricity graphic characteristics of populations as company during the door-to-door well as on the housing and health condi- installation of public provision of elec- tions reveals the importance of the tricity. Some people remove the plate implementation of the HDSS to support and take it with them when moving health research in Angola, and in this from one house to another (within or particular area. without the DSA), causing some distur- At CISA Project, the HDSS is being bance in the field work. These aspects developed in parallel with a Paediatric show the need for strengthening the Clinical Surveillance System and sup- communication strategy with the com- ports a Verbal Autopsy System. Addi- munity. In addition to the frequent con- tionally, the HDSS can be used as a tact with the local leaders, one should sampling frame, as it happened in previ- consider other strategies such as thea- ous studies, namely a malaria, shisto- tre plays for the community, as well as somiasis, geohelminths, anemia and jingles on the radio with short and malnutrition prevalence study (Figueir- accessible messages about the role of edo et al. 2011), and a hypertension the CISA Project and the HDSS. prevalence study. The HDSS is also val- The implementation and the main- uable in allowing for follow-ups of resi- tenance of a HDSS is usually a time and dents during and after an intervention cost consuming challenge. A drawback and cohort studies. Furthermore it aims of these sites is the inability to extrapo- to gather information beyond demogra- late data from a HDSS to extensive phy, as specific sets of questions are areas since the data is typically collected added on subjects like health care on small or isolated areas and is not access and utilization and economic representative of larger populations. welfare and the wellbeing of the house- Another issue relates to the demo- holds. During the 5th update round, graphic characteristics of the study data on housing conditions collected in areas, often marked by migration the initial census was updated and indi- http://aps.journals.ac.za 143 African Population Studies Vol 26, 2 (Nov 2012) cators assessing living standards were ing if it is the result of a sub-representa- collected to allow for the calculation of tion of the former group or indicative of a wealth index of the DSA population. a decline in fertility. The framework of analysis that inte- The weight of women in reproduc- grates those indicators seeks compara- tive ages is very similar in the DSA and bility with other HDSS and Demo- in the national population (46% and graphic Health Surveys. 45%, respectively) as well the number As shown by baseline census data, of young women of childbearing age the population of the DSA has a typical (189 women aged 20-34 per 100 age structure for Angola and other sub- women aged 35-49 in the DSA vs184 in Saharan African countries (COSEP the national territory). 2007 and Nhacolo et al. 2006).There is The sex ratio shows that women a general similarity of several demo- exceed men both in the DSA (98) and graphic indicators in HDSS-Dande and in national population (93). The excep- in the national population according the tion occurs in rural areas of the DSA, Population Wellbeing Survey (PWS) where the number of men exceeds (INEA 2008). Both register a young women in a sex ratio of 102. This might population, as the age ratios confirm, be the result of migrations of young sin- particularly in urban areas. That charac- gle men, coming usually from the south- teristic is more pronounced in the DSA ern provinces (like Benguela and where the young urban represent more Huambo) for farming labour in the than three times the weight of young DSA, or of the labour migration of coal rural (16.7 vs. 5) (Table 1), while in burners coming mostly without family PWS they represent the double (27.4 mainly from within the DSA and Luanda vs. 13.7). province. These migrants are probably There is a particularity in the shape more vulnerable to health threats, as of the DSA pyramid: a reduced number they appear to be living in poorer con- aged 10-19 (compared to the previous ditions, without a social net to which age group 5-9), followed by a protuber- turn to, in case of need. Further studies ance in the age group 20-24. The latter are warranted in order to characterize happens only in urban population, and this population. may be due to a potential attraction exercised by the higher education insti- Conclusions tutions located in Caxito that would This paper aimed to describe the meth- bring young people from Luanda to odology of setting up the DSS-Dande study in Caxito. In the national popula- and give the first glimpse on the popula- tion the number of people in those age tion in surveillance. The HDSS is a plat- groups declines gradually. form which provides the population The ratio of children aged 0-4 and basis for health surveys and will develop 5-9 years shows similar numbers of its full purpose as new research pro- children in both groups in the DSA jects are conducted. The HDSS-Dande (100) that is not present in the national is the first HDSS implemented in the population (where that ratio is 120). region of Central Africa. Further char- Further research will allow understand- acterization of the population in the http://aps.journals.ac.za 144 African Population Studies Vol 26, 2 (Nov 2012)

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