Meta-analysis in epidemiology

Meta-analysis is the structured and systematic qualitative and quantitative integration of the results of several independent studies (Le. the epidemiology of results). As in any epidemiological study, a meta-analysis needs to start with clearly stated aims and objectives. Attention needs to be paid to selection bias in selecting the study population (all publications on the topic). An initial qualitative assessment (conducted blinded to results) categorises projects on the basis of their methods, as unacceptable (dropped from later analysis) and acceptable or good. Further analysis could be conducted by stratifying or weighting independent studies according to preset quality criteria. The quantitative assessment involves deriving a pooled measure of outcome (usually the relative or attributable risk). Tests for heterogeneity are required before pooling. By pooling the results from many settings using different methods, the ability to generalise them in terms of their public health relevance is increased.S Afr Med J 1990; 78: 94·97

Epidemiological research methods. Part VII. Epidemiological research in health planning

CITATION: Yach, D. & Botha, J. L. 1987. Epidemiological research methods. Part VII. Epidemiological research in health planning. South African Medical Journal, 72:633-636.The original publication is available at http://www.samj.org.zaThe goal of epidemiology is to improve the health status of human populations. In our series thus far we have srressed the need to use the correct design for epidemiological studies, a sampling scheme that yields interpretable results, measurements that are both valid and reliable, and finally the appropriate analysis. These methodological considerations are of importance if the goal is to be reached. In this article we assume that most of these issues have been adequately dealt with and focus on how the results of epidemiological research can be used by health planners to improve the health status of regions and the country as a whole.Publisher’s versio

Epidemiological research methods. Part II. Descriptive studies

CITATION: Botha, J. L. & Yach, D. 1986. Epidemiological research methods. Part II. Descriptive studies. South African Medical Journal, 70:766-772.The original publication is available at http://www.samj.org.zaIn a descriptive study, therefore, the magnitude and distribution of a health problem in a specified population is studied in terms of TIME (when did it occur?), PLACE (where did it occur?) and PERSON (which groups are affected?). The design starts with an idea that occurs to the researcher about a particular problem. This is followed by selecting a group of individuals to be studied (sampling), considering which attributes to measure (measurement), describing the findings, and finally drawing conclusions on the basis of the findings. Commonly, new ideas or hypotheses are generated in this final stage, usually regarding possible explanations for the health problems described (cause-effect relationships). Such relationships may be attempts to explain the aetiology of diseases or the effect of preventive, curative or rehabilitative measures. Important issues affecting the reliability of the sampling and measurement processes are discussed, some descriptive statistical measures demonstrated and how conclusions are affected by these, are indicated.Publisher’s versio

Lessons from a small country about the global obesity crisis

Developed countries had high obesity rates before the problem was taken seriously and hence the genesis must be seen in retrospect. Developing countries offer a clear view of causal factors but also opportunities for prevention, which must focus on both food and physical activity environments

An evaluation of the national measles vaccination campaign in the new shanty areas of Khayelitsha

A local component of the national measles vaccination campaign was evaluated in an area undergoing rapid urbanisation near Cape Town. Four serial cross-sectional cluster samples were used. Proven vaccination coverage before the campaign was 55,8% (95% confidence interval (Cl) 46 - 66%), immediately afterwards it was 71,1% (95% Cl 65 - 77%), and 6 months later 73,6% (95% Cl 67 - 80%). The increase was not sustained among Transkei-born children. Significant determinants of vaccination coverage were: place of birth (X2 = 9,7; 2 df; P = 0,008); ≤6 months stay in Cape Town (odds ratio (OR) 2,22; 95% Cl 1,2 - 4,0%); and home birth (OR 3,21; 95% Cl 1,2 - 8,4%). The value of campaigns in controlling measles, as well as the role of a comprehensive health care service are discussed

Missed opportunities for immunisation at hospitals in the western Cape - a reappraisal

Immunisation practices were examined at 6 hospitals in the western Cape during the latter half of 1992 to determine whether these practices had improved subsequent to the February 1991 resolution of the Health Matters Committee (HMC) on immunisation in hospitals, and since a similar study was undertaken in 1990. Exit interviews were conducted with the escorts of all children aged 3 - 59 months who attended the study hospitals on the days designated for the study.In the second study, 88 of the 311 children studied (28,3%) were in need of immunisation on arrival, but only 12 of the 88 (13,6%) were immunised during the hospital visit. There was no evidence of an increase in requests to see children's Road-to-Health cards (37,1% compared with 35,2% previously). The  incidence of missed opportunities for measles immunisation in children aged 6 - 59 months remained unacceptably high (51,4% compared with 63,7% previously, when a strict definition was used; and 15,7% compared with 18,1% previously, when a lenient definition was used).Health authorities at all levels need to take urgent action to address the problem of missed opportunities for immunisation at hospitals

Peering into the black hole - the quality of black mortality data in Por~ Elizabeth and the rest of South Africa

In the year ending 30 June 1989, 26,8% of 5345 deaths in the Port Elizabeth area were classified as ill-defined. A study was undertaken in an attempt to identify the reasons for the high proportion of such deaths. Copies of all death notifications and death register forms of black people in the area served by the Port Elizabeth City Health Department were collected for a 6-week period. Of the 316 deaths, 154 (48,7%) were certified by medical practitioners at a hospital, 158 (50%) by the police and 4 (1,3%) by private medical practitioners. Of the police-certified deaths 116 (73,4%) were recorded as due to 'natural causes', with the remainder being submitted to autopsy. Of the hospital deaths, 26% were not adequately described in the section for the cause of death on the death certificate. Review of national mortality data for 1985 showed that only 29,9% of ill-defined deaths (in all population groups) were certified by a medical practitioner. The prime source of deaths classifed as ill-defined, both in Port Elizabeth and nationally, were those not certified by a medical practitioner. Strategies aimed' at minimising the number of deaths certified by the police need to be developed

Epide·miology of non-fatal injuries due to external causes in Johannesburg-Soweto Part I. Methodology and materials

In this, the first of two articles examining the epidemiology of non-fatal trauma in Johannesburg-Soweto, we define case inclusion criteria, and discuss the methodology and materials used in this low-cost, hospital-based survey. The survey was conducted between 8 June 1989 and 24 August 1990. Sampling of both inpatient trauma cases and those seen in casualty departments took place in 6 state and 5 private hospitals located within or nearby the Johannesburg magisterial district. Demographic details about each patient, as well as information concerning spatial and temporal details of the incident, involvement of alcohol or drugs, diagnosis, severity of injury, and placement after casualty treatment, were collected by interviewing each patient. Data concerning the age, sex and racial composition of the background population were assembled from a number of sources. After discussing the internal limitations of this methodology, it is concluded that its findings may be of limited use for improving secondary interventions, but are of definite value for trauma prevention programmes

Environmental determinants of acute respiratory symptoms and diarrhoea in young coloured children living in urban and peri-urban areas of South Africa

The impact of environmental risk factors associated with housing was examined in relation to diarrhoeal disease and acute respiratory symptoms in South African coloured children. A multistage cluster sample representative of all coloured people living in the major urban and peri-urban areas of South Africa was used for the study. Interviews were conducted with respondents from 1 227 households. Overall, 8,5% children under 5 years were reported to have had diarrhoea, while 29% had experienced coughing and breathing problems in a 2-week recall period. Individual risk factors identified using the odds ratios (ORs) for diarrhoea included not having an inside tap or a flush toilet in the homes (both yielded an OR of 3,3), not owning a refuse receptacle (OR = 2,5), not being connected to an electricity supply (OR = 2,5), low household income (OR = 1,8), more than 2 people per room (OR = 2,0) and less than Standard 5 maternal education (OR = 1,6). Absence of an inside toilet, not having a refuse receptacle and overcrowding all remained as independent risk factors after logistic regression analyses. Multiple logistic regression analyses revealed that not having a refuse receptacle and the absence of electricity for heating purposes were independently associated with respiratory symptoms. The overall preventive potentials for respiratory symptoms were significantly less than those for diarrhoea. Improving physical access to essential environmental health services in urban areas and improvements in the educational status of women are urgently needed if childhood infections are to be prevented

Epidemiology of non-fatal injuries due to external causes in Johannesburg-Soweto Part 11. Incidence and determinants

A total of 3535 trauma cases were enumerated in Johannesburg- Soweto between 1989 and 1990 in the course of 271 hospital ward rounds and 43 casualty watches. The overall trauma incidence was 2886 new cases per annum per 100000 population, rising to 19872 for coloured males aged 20 - 24 years and to 8761 for black males aged 20 - 24 years. Overall the malelfemale ratio was 2,9 rising to 6 or more in adolescence (15 - 19) for blacks andcoloureds. There were some 156 new resident cases of trauma daily; half these were victims of interpersonal violence, and coloureds constituted 22% of this group, although forming only 8% of the denominator population. Witluegards to cause, most trauma among blacks and coloureds arose from interpersonal violence and significantly less from transport accidents. Among blacks injured in transport accidents (the majority of which involved motor vehicles) most were pedestrians, whereas most whites injured in such accidents were occupants of vehicles. For all groups trauma was most likely to be incurred 'in the street' although for white and coloured women the home was most dangerous. The implications of these and related findings for treatment and prevention and briefly reviewed