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Precipitation variability in Sao Paulo State, Brazil

DUFEK, A. S.; AMBRIZZI, T.
Fonte: SPRINGER WIEN Publicador: SPRINGER WIEN
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
25.96%
The State of Sao Paulo is the richest in Brazil, responsible for over 30% of the Brazilian gross rate. It has a population of around 30 million and its economy is based on agriculture and industrial products. Any change in climate can have a profound influence on the socio-economics of the State. In order to determine changes in total and extreme rainfall over Sao Paulo State, climate change indices derived from daily precipitation data were calculated using specially designed software. Maps of trends for a subset of 59 rain gauge stations were analysed for the period 1950-1999 and also for a subset of this period, 1990-1999, representing more recent climate. A non-parametric Mann-Kendall test was applied to the time series. Maps of trends for six annual precipitation indices (annual total precipitation (PRCPTOT), very heavy precipitation days (R20mm), events greater than the 95th percentile (R95p), maximum five days precipitation total (RX5day), the length of the largest wet spell (CWD) and the length of the largest dry spell (CDD)) were analysed for the entire period. These exhibited statistically significant trends associated with a wetter climate. A significant increase in PRCPTOT, associated with very heavy precipitation days...

Global interannual trends and amplitude modulations of the sea surface height anomaly from the TOPEX/Jason-1 altimeters

POLITO, Paulo S.; SATO, Olga T.
Fonte: AMER METEOROLOGICAL SOC Publicador: AMER METEOROLOGICAL SOC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
25.96%
This study uses the global Ocean Topography Experiment (TOPEX)/Jason-1 altimeters` time series to estimate the 13-yr trend in sea surface height anomaly. These trends are estimated at each grid point by two methods: one fits a straight line to the time series and the other is based on the difference between the average height between the two halves of the time series. In both cases the trend shows large regional variability, mostly where the intense western boundary currents turn. The authors hypothesize that the regional variability of the sea surface height trends leads to changes in the local geostrophic transport. This in turn affects the instability-related processes that generate mesoscale eddies and enhances the Rossby wave signals. This hypothesis is verified by estimates of the trend of the amplitude of the filtered sea surface height anomaly that contains the spectral bands associated with Rossby waves and mesoscale eddies. The authors found predominantly positive tendency in the amplitude of Rossby waves and eddies, which suggests that, on average, these events are becoming more energetic. In some regions, the variation in amplitude over 13 yr is comparable to the standard deviation of the data and is statistically significant according to both methods employed in this study. It is plausible that in this case...

Modeling extreme minimum air temperature series under climate change conditions

Blain,Gabriel Constantino
Fonte: Universidade Federal de Santa Maria Publicador: Universidade Federal de Santa Maria
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2011 EN
Relevância na Pesquisa
25.96%
Considering the presence of non-stationary components, such as trends, in the extreme minimum air temperature series available from three locations of the State of São Paulo-Brazil, the aim of this research was to describe the probabilistic structure of this variable by using a non-stationary model (based on the general extreme value distribution; GEV model) in which the parameters are estimated as a function of time covariate. The Mann-Kendall test has proven the presence of significant increasing trends in all analyzed series. Furthermore, according to the Pettitt (changing-point) test, 1991 is the initial year of these trends (in the three locations). The applied selection criteria indicated that a GEV model in which the location parameter is estimated as a function of time is recommended to describe the probability structure of the variable under evaluation. The others two parameters of this model remained time-independent. According to this non-stationary model, the detected trends in the climate conditions of these locations have shown the same rate of change (0.04°C per year).

Analysis of interrupted time series mortality trends: an example to evaluate regionalized perinatal care.

Gillings, D; Makuc, D; Siegel, E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1981 EN
Relevância na Pesquisa
25.94%
Interrupted time series designs are frequently employed to evaluate program impact. Analysis strategies to determine if shifts have occurred are not well known. The case where statistical fluctuations (errors) may be assumed independent is considered, and a segmented regression methodology presented. The method discussed ia applied to the assessment of changes in local and state perinatal postneonatal mortality to identify historical trends and will be used to evaluate the impact of the North Carolina Regionalized Perinatal Care Program when seven years of post-program mortality data become available. The perinatal program region is contrasted with a control region to provide a basis for interpretation of differences noted. Relevant segmented regression models provided good fits to the data and highlighted mortality trends over the last 30 years. Considerable racial differences in these trends were identified, particularly for postneonatal mortality. Segmented regression is considered relevant for the analysis of interrupted time series designs in other applications when errors can be taken to be independent. Thus, the methodology may be regarded as a general statistical tool for evaluation purposes.

Path analysis of family resemblance with temporal trends: applications to height, weight, and Quetelet index in northeastern Brazil.

Province, M A; Rao, D C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1985 EN
Relevância na Pesquisa
25.96%
A multifactorial model incorporating temporal trends in its parameters is discussed. The model is a generalization of the tau model of Rice et al. in which the parameters are assumed to be specific functions of time. A special case of this model is fit to data on height, weight, and Quetelet index in 1,067 nuclear families to demonstrate the utility of the approach. The results indicate that there is considerable temporal variation in family resemblance over time for all three traits. For height and Quetelet index, both the transmissibility, comparable to heritability, and residual sibling environmental correlation show temporal changes, while for weight, only the latter exhibits significant trends. Trends were not found in the marital correlation for any of the traits, and only limited evidence was found for trends in the maternal transmission parameter for height. This provides an objective method for evaluating the nature and sources of temporal trends in family resemblance, which can easily be incorporated into the framework of any model-based approach.

Health transitions in sub-Saharan Africa: overview of mortality trends in children under 5 years old (1950-2000).

Garenne, Michel; Gakusi, Enéas
Fonte: World Health Organization Publicador: World Health Organization
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
25.96%
OBJECTIVE: To reconstruct and analyse mortality trends in children younger than 5 years in sub-Saharan Africa between 1950 and 2000. METHODS: We selected 66 Demographic and Health Surveys and World Fertility Surveys from 32 African countries for analysis. Death rates were calculated by yearly periods for each survey. When several surveys were available for the same country, overlapping years were combined. Country-specific time series were analysed to identify periods of monotonic trends, whether declining, steady or increasing. We tested changes in trends using a linear logistic model. FINDINGS: A quarter of the countries studied had monotonic declining mortality trends: i.e. a smooth health transition. Another quarter had long-term declines with some minor rises over short periods of time. Eight countries had periods of major increases in mortality due to political or economic crises, and in seven countries mortality stopped declining for several years. In eight other countries mortality has risen in recent years as a result of paediatric AIDS. Reconstructed levels and trends were compared with other estimates made by international organizations, usually based on indirect methods. CONCLUSION: Overall, major progress in child survival was achieved in sub-Saharan Africa during the second half of the twentieth century. However...

Detection of Practice Pattern Trends through Natural Language Processing of Clinical Narratives and Biomedical Literature

Chen, Elizabeth S.; Stetson, Peter D.; Lussier, Yves A.; Markatou, Marianthi; Hripcsak, George; Friedman, Carol
Fonte: American Medical Informatics Association Publicador: American Medical Informatics Association
Tipo: Artigo de Revista Científica
Publicado em //2007; 2007 EN
Relevância na Pesquisa
25.94%
Clinical knowledge, best evidence, and practice patterns evolve over time. The ability to track these changes and study practice trends may be valuable for performance measurement and quality improvement efforts. The goal of this study was to assess the feasibility and validity of methods to generate and compare trends in biomedical literature and clinical narrative. We focused on the challenge of detecting trends in medication usage over time for two diseases: HIV/AIDS and asthma. Information about disease-specific medications in published randomized control trials and discharge summaries at New York-Presbyterian Hospital over a ten-year period were extracted using Natural Language Processing. This paper reports on the ability of our semi-automated process to discover disease-drug practice pattern trends and interpretation of findings across the biomedical and clinical text sources.

Increasing Clinical Virulence in Two Decades of the Italian HIV Epidemic

Müller, Viktor; Maggiolo, Franco; Suter, Fredy; Ladisa, Nicoletta; De Luca, Andrea; Antinori, Andrea; Sighinolfi, Laura; Quiros-Roldan, Eugenia; Carosi, Giampiero; Torti, Carlo
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
25.96%
The recent origin and great evolutionary potential of HIV imply that the virulence of the virus might still be changing, which could greatly affect the future of the pandemic. However, previous studies of time trends of HIV virulence have yielded conflicting results. Here we used an established methodology to assess time trends in the severity (virulence) of untreated HIV infections in a large Italian cohort. We characterized clinical virulence by the decline slope of the CD4 count (n = 1423 patients) and the viral setpoint (n = 785 patients) in untreated patients with sufficient data points. We used linear regression models to detect correlations between the date of diagnosis (ranging 1984–2006) and the virulence markers, controlling for gender, exposure category, age, and CD4 count at entry. The decline slope of the CD4 count and the viral setpoint displayed highly significant correlation with the date of diagnosis pointing in the direction of increasing virulence. A detailed analysis of riskgroups revealed that the epidemics of intravenous drug users started with an apparently less virulent virus, but experienced the strongest trend towards steeper CD4 decline among the major exposure categories. While our study did not allow us to exclude the effect of potential time trends in host factors...

Trends in Inequalities in Induced Abortion According to Educational Level among Urban Women

Pérez, Gloria; García-Subirats, Irene; Rodríguez-Sanz, Maica; Díez, Elia; Borrell, Carme
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
25.94%
This study aims to describe trends in inequalities by women’s socioeconomic position and age in induced abortion in Barcelona (Spain) over 1992–1996 and 2000–2004. Induced abortions occurring in residents in Barcelona aged 20 and 44 years in the study period are included. Variables are age, educational level, and time periods. Induced abortion rates per 1,000 women and absolute differences for educational level, age, and time period are calculated. Poisson regression models are fitted to obtain the relative risk (RR) for trends. Induced abortion rates increased from 10.1 to 14.6 per 1,000 women aged 20–44 (RR = 1.44; 95% confidence interval (CI) 1.41–1.47) between 1992–1996 and 2000–2004. The abortion rate was highest among women aged 20–24 and 25–34 and changed little among women aged 35–44. Among women aged 20–24 and 25–34, those with a primary education or less had higher rates of induced abortion in the second period. Induced abortion rates also grew in those women with secondary education. In the 35–44 age group, the induced abortion rate declined among women with a secondary education (RR = 0.66; 95% CI 0.60–0.73) and slightly among those with a greater level of education. Induced abortion is rising most among women in poor socioeconomic positions. This study reveals deep inequalities in induced abortion in Barcelona...

Childhood brain tumours and use of mobile phones: comparison of a case–control study with incidence data

Aydin, Denis; Feychting, Maria; Schüz, Joachim; Röösli, Martin
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 20/05/2012 EN
Relevância na Pesquisa
25.96%
The first case–control study on mobile phone use and brain tumour risk among children and adolescents (CEFALO study) has recently been published. In a commentary published in Environmental Health, Söderqvist and colleagues argued that CEFALO suggests an increased brain tumour risk in relation to wireless phone use. In this article, we respond and show why consistency checks of case–control study results with observed time trends of incidence rates are essential, given the well described limitations of case–control studies and the steep increase of mobile phone use among children and adolescents during the last decade. There is no plausible explanation of how a notably increased risk from use of wireless phones would correspond to the relatively stable incidence time trends for brain tumours among children and adolescents observed in the Nordic countries. Nevertheless, an increased risk restricted to heavy mobile phone use, to very early life exposure, or to rare subtypes of brain tumours may be compatible with stable incidence trends at this time and thus further monitoring of childhood brain tumour incidence rate time trends is warranted.

Increased Upper and Lower Tract Urothelial Carcinoma in Patients with End-Stage Renal Disease: A Nationwide Cohort Study in Taiwan during 1997–2008

Wang, Shuo-Meng; Lai, Ming-Nan; Chen, Pau-Chung; Pu, Yeong-Shiau; Lai, Ming-Kuen; Hwang, Jing-Shiang; Wang, Jung-Der
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
25.94%
Background. Urothelial cancer (UC) is the leading cancer of patients with end-stage renal disease (ESRD) in Taiwan. The aims of this study were to explore the time trends of UC incidences and propose possible etiologic factors. Methods. Abstracting from the National Health Insurance Research Database (NHIRD), there were 90,477 newly diagnosed cases of ESRD between 1997 and 2008 covering the patients aged 40–85. Among them, 2,708 had developed UC after diagnosis of ESRD. The CIR40–85 (cumulative incidence rate) of upper tract UC (UTUC) and lower tract UC (LTUC) were calculated for ESRD patients and general population, as well as SIR40–85 (standardized incidence ratio) for comparison. Results. Female ESRD patients were found to have 9–18 times of elevated risks of UC, while those of males were increased up to 4–14 times. The time trends of CIR40–84 and SIR40–84 of UTUC in females appear to decline after calendar year 2000. These trends may be related to AA associated herbal products after 1998. Conclusions. Patients with ESRD are at increased risks for both LTUC and UTUC in Taiwan. We hypothesize that the time trends associate with the consumption of aristolochic acid in Chinese herbal products (female predominant).

Changes in Trace Metal Trends Over Time in a Rural Lake in Southern Ontario: Evaluation of Potential Metal Sources and Sediment Quality in Kahshe Lake

Angelo, Amy
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN
Relevância na Pesquisa
25.96%
Kahshe Lake is located in the Muskoka-Haliburton region of Southern Ontario. The lake has no known point sources of metal contaminants and the surrounding catchment has been altered by shoreline cottage development. One core sample was taken from the deepest part of the lake in July, 2009 and was analysed by Inductively Coupled Plasma-Optical Emissions Spectroscopy (ICP-OES) for metal concentrations. Metals included in the study are As, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, S and Zn. The primary objectives of the study include: 1) determining which metals are present within the lake in pre-twentieth century levels; 2) determining which elements exist in elevated or decreased concentrations when compared to pre-twentieth century levels; 3) to give a qualitative assessment of which metals, if any, pose a risk to biota within the lake system using Interim Sediment Quality Guidelines (ISQG) and Probable Effect Levels (PEL); and 4) determining if any elemental trends are associated in order to speculate on a common emission sources. All metals except K and Mg (for which concentrations declined in surface sediment relative to sediment at the bottom of the core) showed elevation above pre-twentieth century concentrations over time. Percent increases from pre-twentieth century levels were highest for Pb (677.7%)...

Vector Autoregressive Models

LUETKEPOHL, Helmut
Fonte: Instituto Universitário Europeu Publicador: Instituto Universitário Europeu
Tipo: Trabalho em Andamento Formato: application/pdf; digital
EN
Relevância na Pesquisa
25.96%
Multivariate simultaneous equations models were used extensively for macroeconometric analysis when Sims (1980) advocated vector autoregressive (VAR) models as alternatives. At that time longer and more frequently observed macroeconomic time series called for models which described the dynamic structure of the variables. VAR models lend themselves for this purpose. They typically treat all variables as a priori endogenous. Thereby they account for Sims’ critique that the exogeneity assumptions for some of the variables in simultaneous equations models are ad hoc and often not backed by fully developed theories. Restrictions, including exogeneity of some of the variables, may be imposed on VAR models based on statistical procedures. VAR models are natural tools for forecasting. Their setup is such that current values of a set of variables are partly explained by past values of the variables involved. They can also be used for economic analysis, however, because they describe the joint generation mechanism of the variables involved. Structural VAR analysis attempts to investigate structural economic hypotheses with the help of VAR models. Impulse response analysis, forecast error variance decompositions, historical decompositions and the analysis of forecast scenarios are the tools which have been proposed for disentangling the relations between the variables in a VAR model. Traditionally VAR models are designed for stationary variables without time trends. Trending behavior can be captured by including deterministic polynomial terms. In the 1980s the discovery of the importance of stochastic trends in economic variables and the development of the concept of cointegration by Granger (1981)...

Recent trends in agricultural production of Africa based on AVHRR NDVI time series

VRIELING Anton; DE BEURS Kirsten; BROWN Molly
Fonte: SPIE Europe Publicador: SPIE Europe
Tipo: Contributions to Conferences Formato: Printed
ENG
Relevância na Pesquisa
25.96%
African agriculture is expected to be hard-hit by ongoing climate change. Effects are heterogeneous within the continent, but in some regions resulting production declines have already impacted food security. Time series of remote sensing data allow us to examine where persistent changes occur. In this study, we propose to examine recent trends in agricultural production using 26 years of NDVI data. We use the 8-km resolution AVHRR NDVI 15-day composites of the GIMMS group (1981-2006). Temporal data-filtering is applied using an iterative Savitzky-Golay algorithm to remove noise in the time series. Except for some regions with persistent cloud cover, this filter produced smooth profiles. Subsequently two methods were used to extract phenology indicators from the profiles for each raster cell. These indicators include start of season, length of season, time of maximum NDVI, maximum NDVI, and cumulated NDVI over the season. Having extracted the indicators for every year, we aggregate them for agricultural areas at sub-national level using a crop mask. The aggregation was done to focus the analysis on agriculture, and allow future comparison with yield statistics. Trend analysis was performed for yearly aggregated indicators to assess where persistent change occurred during the 26-year period. Results show that the phenology extraction method chosen has an important influence on trend outcomes. Consistent trends suggest a rising yield trend for 500-1100 mm rainfall zones ranging from Senegal to Sudan. Negative yield trends are expected for the southern Atlantic coast of West Africa...

Near-term projection of anthropogenic emission trends using neural networks

BALSAMA Alessia; DEBIASE Lucia; JANSSENS-MAENHOUT Greet; PAGLIARI VALERIO
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Articles in Journals Formato: Online
ENG
Relevância na Pesquisa
25.96%
This study analyses for the first time the global time series 1970-2008 of the Emissions Database for Global Atmospheric Research (EDGAR) for 10 chemical species and more than 3000 subsectors with neural networks, looking for non-linear behaviours that several species bear in common. The application of the different neural network types, suggests that General Regression Neural Networks (GRNN) are more adequate to train a typical Gaussian trend with a very low error. As such, GRNN are very suitable to complete the database for some missing data points within the time-series of the database, but they are not so good for a projection outside the database time period. Instead Multi Layers Perceptron (MLP) is very adequate for projecting for a subsequent year to the database time period, even though MLP is characterised by a slightly higher absolute mean error than the GRNN. By means of the Principal Component Analysis (PCA) we identified which chemical substances are driven similarly by the activity data over the almost 40 years time period. We observed that in all the geographic aggregations the emission trends of CO2, SO2 and NOX can be grouped into one cluster, and the emission trends of CH4 and the particulates in another cluster. The best interval time for the prediction proved to be eleven years and projections seemed to be reliable for three consecutive years following the last year of the database time-series.; JRC.H.2-Air and Climate

Real-Time Classification of Twitter Trends

Zubiaga, Arkaitz; Spina, Damiano; Martínez, Raquel; Fresno, Víctor
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/03/2014
Relevância na Pesquisa
25.96%
Social media users give rise to social trends as they share about common interests, which can be triggered by different reasons. In this work, we explore the types of triggers that spark trends on Twitter, introducing a typology with following four types: 'news', 'ongoing events', 'memes', and 'commemoratives'. While previous research has analyzed trending topics in a long term, we look at the earliest tweets that produce a trend, with the aim of categorizing trends early on. This would allow to provide a filtered subset of trends to end users. We analyze and experiment with a set of straightforward language-independent features based on the social spread of trends to categorize them into the introduced typology. Our method provides an efficient way to accurately categorize trending topics without need of external data, enabling news organizations to discover breaking news in real-time, or to quickly identify viral memes that might enrich marketing decisions, among others. The analysis of social features also reveals patterns associated with each type of trend, such as tweets about ongoing events being shorter as many were likely sent from mobile devices, or memes having more retweets originating from a few trend-setters.; Comment: Pre-print of article accepted for publication in Journal of the American Society for Information Science and Technology copyright @ 2013 (American Society for Information Science and Technology)

Long-range correlations and trends in Colombian seismic time series

Martin-Montoya, L. A.; Aranda-Camacho, N. M.; Quimbay, C. J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
25.95%
We study long-range correlations and trends in time series extracted from the data of seismic events occurred from 1973 to 2011 in a rectangular region that contains mainly all the continental part of Colombia. The long-range correlations are detected by the calculation of the Hurst exponents for the time series of interevent intervals, separation distances, depth differences and magnitude differences. By using a modification of the classical $R/S$ method that has been developed to detect short-range correlations in time series, we find the existence of persistence for all the time series considered except for magnitude differences. We find also, by using the $DFA$ until the third order, that the studied time series are not influenced by trends. Additionally, an analysis of the Hurst exponent as a function of the number of events in the time and the maximum window size is presented.; Comment: 21 pages, 6 figures, 2 figures added, types corrected, accepted to be published in Physica A

A Latent Source Model for Nonparametric Time Series Classification

Chen, George H.; Nikolov, Stanislav; Shah, Devavrat
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
25.96%
For classifying time series, a nearest-neighbor approach is widely used in practice with performance often competitive with or better than more elaborate methods such as neural networks, decision trees, and support vector machines. We develop theoretical justification for the effectiveness of nearest-neighbor-like classification of time series. Our guiding hypothesis is that in many applications, such as forecasting which topics will become trends on Twitter, there aren't actually that many prototypical time series to begin with, relative to the number of time series we have access to, e.g., topics become trends on Twitter only in a few distinct manners whereas we can collect massive amounts of Twitter data. To operationalize this hypothesis, we propose a latent source model for time series, which naturally leads to a "weighted majority voting" classification rule that can be approximated by a nearest-neighbor classifier. We establish nonasymptotic performance guarantees of both weighted majority voting and nearest-neighbor classification under our model accounting for how much of the time series we observe and the model complexity. Experimental results on synthetic data show weighted majority voting achieving the same misclassification rate as nearest-neighbor classification while observing less of the time series. We then use weighted majority to forecast which news topics on Twitter become trends...

Testing and estimation of models with stochastic trends.

Busetti, Fabio
Fonte: London School of Economics and Political Science Thesis Publicador: London School of Economics and Political Science Thesis
Tipo: Thesis; NonPeerReviewed Formato: application/pdf
Publicado em //2001 EN
Relevância na Pesquisa
25.96%
The thesis considers time series and econometric models with stochastic trend components. Locally Best Invariant tests for the presence of stochastic trends are constructed and their asymptotic distributions derived. Particular attention is paid to models with structural breaks, as the tests have high power also against alternative hypotheses in which the trends of the series contain a small number of breaks but are otherwise deterministic. Asymptotic critical values of the tests are tabulated for series with a single breakpoint. A modification of the LBI statistic is then proposed, for which the asymptotic distribution depends only on the number of the breaks and not on their location. Common stochastic trends imply cointegration and thus testing the number of common trends can also be regarded as testing the dimension of the cointegration space. A test for common trends recently proposed in the literature is extended to series which contain structural breaks. Testing for the presence of a nonstationary seasonal component is then examined. The LBI test, adjusted for serial correlation by means of a nonparametric correction, is extended in various directions and its performance is compared with that of a parametric test. Representation...

Health transitions in sub-Saharan Africa: overview of mortality trends in children under 5 years old (1950-2000)

Garenne,Michel; Gakusi,Enéas
Fonte: World Health Organization Publicador: World Health Organization
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2006 EN
Relevância na Pesquisa
25.96%
OBJECTIVE: To reconstruct and analyse mortality trends in children younger than 5 years in sub-Saharan Africa between 1950 and 2000. METHODS: We selected 66 Demographic and Health Surveys and World Fertility Surveys from 32 African countries for analysis. Death rates were calculated by yearly periods for each survey. When several surveys were available for the same country, overlapping years were combined. Country-specific time series were analysed to identify periods of monotonic trends, whether declining, steady or increasing. We tested changes in trends using a linear logistic model. FINDINGS: A quarter of the countries studied had monotonic declining mortality trends: i.e. a smooth health transition. Another quarter had long-term declines with some minor rises over short periods of time. Eight countries had periods of major increases in mortality due to political or economic crises, and in seven countries mortality stopped declining for several years. In eight other countries mortality has risen in recent years as a result of paediatric AIDS. Reconstructed levels and trends were compared with other estimates made by international organizations, usually based on indirect methods. CONCLUSION: Overall, major progress in child survival was achieved in sub-Saharan Africa during the second half of the twentieth century. However...