| 1. |
- Musenge, Eustasius, et al.
(författare)
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Bayesian analysis of zero inflated spatiotemporal HIV/TB child mortality data through the INLA and SPDE approaches : applied to data observed between 1992 and 2010 in rural North East South Africa
- 2013
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Ingår i: International Journal of Applied Earth Observation and Geoinformation. - : Elsevier BV. - 1569-8432 .- 1872-826X. ; 22, s. 86-98
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Tidskriftsartikel (refereegranskat)abstract
- Longitudinal mortality data with few deaths usually have problems of zero-inflation. This paper presents and applies two Bayesian models which cater for zero-inflation, spatial and temporal random effects. To reduce the computational burden experienced when a large number of geo-locations are treated as a Gaussian field (GF) we transformed the field to a Gaussian Markov Random Fields (GMRF) by triangulation. We then modelled the spatial random effects using the Stochastic Partial Differential Equations (SPDEs). Inference was done using a computationally efficient alternative to Markov chain Monte Carlo (MCMC) called Integrated Nested Laplace Approximation (INLA) suited for GMRF. The models were applied to data from 71,057 children aged 0 to under 10 years from rural north-east South Africa living in 15,703 households over the years 1992-2010. We found protective effects on HIV/TB mortality due to greater birth weight, older age and more antenatal clinic visits during pregnancy (adjusted RR (95% CI)): 0.73(0.53;0.99), 0.18(0.14;0.22) and 0.96(0.94;0.97) respectively. Therefore childhood HIV/TB mortality could be reduced if mothers are better catered for during pregnancy as this can reduce mother-to-child transmissions and contribute to improved birth weights. The INLA and SPDE approaches are computationally good alternatives in modelling large multilevel spatiotemporal GMRF data structures.
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| 2. |
- Ngongondo, Cosmo S., et al.
(författare)
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Regional frequency analysis of rainfall extremes in Southern Malawi using the index rainfall and L-moments approaches
- 2011
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Ingår i: Stochastic environmental research and risk assessment (Print). - : Springer Science and Business Media LLC. - 1436-3240 .- 1436-3259. ; 25:7, s. 939-955
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Tidskriftsartikel (refereegranskat)abstract
- Rainfall extremes often result in the occurrence of flood events with associated loss of life and infrastructure in Malawi. However, an understanding of the frequency of occurrence of such extreme events either for design or disaster planning purposes is often limited by data availability at the desired temporal and spatial scales. Regionalisation, which involves "trading time for space" by pooling together observations for stations with similar behavior, is an alternative approach for more accurate determination of extreme events even at ungauged areas or sites with short records. In this study, regional frequency analysis of rainfall extremes in Southern Malawi, large parts of which are flood prone, was undertaken. Observed 1-, 3-, 5- and 7-day annual maximum rainfall series for the period 1978-2007 at 23 selected rainfall stations in Southern Malawi were analysed. Cluster analysis using scaled at-site characteristics was used to determine homogeneous rainfall regions. L-moments were applied to derive regional index rainfall quantiles. The procedure also validated the three rainfall regions identified through homogeneity and heterogeneity tests based on Monte Carlo simulations with regional average L-moment ratios fitted to the Kappa distribution. Based on assessments of the accuracy of the derived index rainfall quantiles, it was concluded that the performance of this regional approach was satisfactory when validated for sites not included in the sample data. The study provides an estimate of the regional characteristics of rainfall extremes that can be useful in among others flood mitigation and engineering design.
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| 3. |
- Thorogood, Margaret, et al.
(författare)
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The Nkateko health service trial to improve hypertension management in rural South Africa : study protocol for a randomised controlled trial
- 2014
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Ingår i: Trials. - : Springer Science and Business Media LLC. - 1745-6215. ; 15, s. 435-
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Tidskriftsartikel (refereegranskat)abstract
- Background: South Africa has a high and rising prevalence of hypertension. Many affected individuals are not using medication, and few have controlled blood pressure. Until recently, primary care clinics focused on maternal and child health and management of acute conditions, but new government initiatives have shifted the focus to chronic diseases, including HIV/AIDS and hypertension.Methods/Design: The Nkateko trial will test the effectiveness of clinic-based lay health workers (LHWs) in supporting hypertension management. It is a pragmatic, cluster randomised controlled trial based in the Agincourt subdistrict of northeast South Africa, and it is underpinned by long-term health and demographic surveillance. Eight primary care facilities, with their catchment communities, are randomised to usual care or the addition of LHWs focused on chronic care. All clinics (intervention and control) will be provided with a clerk to collect information on clinic attendees and will match them to preexisting surveillance records. Intervention clinics will have LHWs working alongside nursing staff and focusing on health care for people with chronic conditions, particularly hypertension. The LHWs will be supported by an implementation manager, who will work with clinic staff to develop the most effective role for the LHWs. Control clinics will continue to provide usual care. The primary outcome will be the change between two population surveys conducted before and after the intervention in the proportion of the population with uncontrolled hypertension and a risk profile indicating at least moderate risk of cardiovascular disease. A process evaluation will be based on a realist approach using patient exit interviews, clinic observations and interviews with health professionals, LHWs and patients to document the intervention and its implementation.Discussion: There are challenges in the design of this trial. Assessing change through population surveys may reduce measurable effects; however, we feel this is appropriate because we aim to attract those who currently do not use clinics, and we hope to improve care for clinic users. Clinics were randomised at an open meeting because we were concerned that a remote process of randomisation would not be trusted by the community. We are constantly working to achieve an effective balance between the intervention and process evaluations.
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