196 research outputs found
Semiparametric Bayesian Density Estimation with Disparate Data Sources: A Meta-Analysis of Global Childhood Undernutrition
Undernutrition, resulting in restricted growth, and quantified here using
height-for-age z-scores, is an important contributor to childhood morbidity and
mortality. Since all levels of mild, moderate and severe undernutrition are of
clinical and public health importance, it is of interest to estimate the shape
of the z-scores' distributions.
We present a finite normal mixture model that uses data on 4.3 million
children to make annual country-specific estimates of these distributions for
under-5-year-old children in the world's 141 low- and middle-income countries
between 1985 and 2011. We incorporate both individual-level data when
available, as well as aggregated summary statistics from studies whose
individual-level data could not be obtained. We place a hierarchical Bayesian
probit stick-breaking model on the mixture weights. The model allows for
nonlinear changes in time, and it borrows strength in time, in covariates, and
within and across regional country clusters to make estimates where data are
uncertain, sparse, or missing.
This work addresses three important problems that often arise in the fields
of public health surveillance and global health monitoring. First, data are
always incomplete. Second, different data sources commonly use different
reporting metrics. Last, distributions, and especially their tails, are often
of substantive interest.Comment: 41 total pages, 6 figures, 1 tabl
Childrenās height and weight in rural and urban populations in low-income and middle-income countries: a systematic analysis of population-representative data
Background Urban living aff ects childrenās nutrition and growth, which are determinants of their survival, cognitive
development, and lifelong health. Little is known about urbanārural diff erences in childrenās height and weight, and
how these diff erences have changed over time. We aimed to investigate trends in childrenās height and weight in rural
and urban settings in low-income and middle-income countries, and to assess changes in the urbanārural diff erentials
in height and weight over time.
Methods We used comprehensive population-based data and a Bayesian hierarchical mixture model to estimate
trends in childrenās height-for-age and weight-for-age Z scores by rural and urban place of residence, and changes in
urbanārural diff erentials in height and weight Z scores, for 141 low-income and middle-income countries between
1985 and 2011. We also estimated the contribution of changes in rural and urban height and weight, and that of
urbanisation, to the regional trends in these outcomes.
Findings Urban children are taller and heavier than their rural counterparts in almost all low-income and middleincome
countries. The urbanārural diff erential is largest in Andean and central Latin America (eg, Peru, Honduras,
Bolivia, and Guatemala); in some African countries such as Niger, Burundi, and Burkina Faso; and in Vietnam and
China. It is smallest in southern and tropical Latin America (eg, Chile and Brazil). Urban children in China, Chile,
and Jamaica are the tallest in low-income and middle-income countries, and children in rural areas of Burundi,
Guatemala, and Niger the shortest, with the tallest and shortest more than 10 cm apart at age 5 years. The heaviest
children live in cities in Georgia, Chile, and China, and the most underweight in rural areas of Timor-Leste, India,
Niger, and Bangladesh. Between 1985 and 2011, the urban advantage in height fell in southern and tropical Latin
America and south Asia, but changed little or not at all in most other regions. The urbanārural weight diff erential also decreased in southern and tropical Latin America, but increased in east and southeast Asia and worldwide, because weight gain of urban children outpaced that of rural children.Interpretation Further improvement of child nutrition will require improved access to a stable and aff ordable food supply and health care for both rural and urban children, and closing of the the urbanārural gap in nutritional status
Measuring Infertility in Populations: Constructing a Standard Definition for Use with Demographic and Reproductive Health Surveys
Background: Infertility is a significant disability, yet there are no reliable estimates of its global prevalence. Studies on infertility prevalence define the condition inconsistently, rendering the comparison of studies or quantitative summaries of the literature difficult. This study analyzed key components of infertility to develop a definition that can be consistently applied to globally available household survey data.
Methods: We proposed a standard definition of infertility and used it to generate prevalence estimates using 53 Demographic and Health Surveys (DHS). The analysis was restricted to the subset of DHS that contained detailed fertility information collected through the reproductive health calendar. We performed sensitivity analyses for key components of the definition and used these to inform our recommendations for each element of the definition
Trends in adult body-mass index in 200 countries from 1975 to 2014: a pooled analysis of 1698 population-based measurement studies with 19.2 million participants
Background Underweight and severe and morbid obesity are associated with highly elevated risks of adverse health outcomes. We estimated trends in mean body-mass index (BMI), which characterises its population distribution, and in the prevalences of a complete set of BMI categories for adults in all countries. Methods We analysed, with use of a consistent protocol, population-based studies that had measured height and weight in adults aged 18 years and older. We applied a Bayesian hierarchical model to these data to estimate trends from 1975 to 2014 in mean BMI and in the prevalences of BMI categories (<18.5 kg/m2[underweight], 18.5 kg/m2to <20 kg/m2, 20 kg/m2to <25 kg/m2, 25 kg/m2to <30 kg/m2, 30 kg/m2to <35 kg/m2, 35 kg/m2to <40 kg/m2, ā„40 kg/m2[morbid obesity]), by sex in 200 countries and territories, organised in 21 regions. We calculated the posterior probability of meeting the target of halting by 2025 the rise in obesity at its 2010 levels, if post-2000 trends continue. Findings We used 1698 population-based data sources, with more than 19.2 million adult participants (9.9 million men and 9.3 million women) in 186 of 200 countries for which estimates were made. Global age-standardised mean BMI increased from 21.7 kg/m2(95% credible interval 21.3-22.1) in 1975 to 24.2 kg/m2(24.0-24.4) in 2014 in men, and from 22.1 kg/m2(21.7-22.5) in 1975 to 24.4 kg/m2(24.2-24.6) in 2014 in women. Regional mean BMIs in 2014 for men ranged from 21.4 kg/m2in central Africa and south Asia to 29.2 kg/m2(28.6-29.8) in Polynesia and Micronesia; for women the range was from 21.8 kg/m2(21.4-22.3) in south Asia to 32.2 kg/m2(31.5-32.8) in Polynesia and Micronesia. Over these four decades, age-standardised global prevalence of underweight decreased from 13.8% (10.5-17.4) to 8.8% (7.4-10.3) in men and from 14.6% (11.6-17.9) to 9.7% (8.3-11.1) in women. South Asia had the highest prevalence of underweight in 2014, 23.4% (17.8-29.2) in men and 24.0% (18.9-29.3) in women. Age-standardised prevalence of obesity increased from 3.2% (2.4-4.1) in 1975 to 10.8% (9.7-12.0) in 2014 in men, and from 6.4% (5.1-7.8) to 14.9% (13.6-16.1) in women. 2.3% (2.0-2.7) of the world's men and 5.0% (4.4-5.6) of women were severely obese (ie, have BMI ā„35 kg/m2). Globally, prevalence of morbid obesity was 0.64% (0.46-0.86) in men and 1.6% (1.3-1.9) in women. Interpretation If post-2000 trends continue, the probability of meeting the global obesity target is virtually zero. Rather, if these trends continue, by 2025, global obesity prevalence will reach 18% in men and surpass 21% in women; severe obesity will surpass 6% in men and 9% in women. Nonetheless, underweight remains prevalent in the world's poorest regions, especially in south Asia
Supporting information for National, regional, and worldwide estimates of low birthweight rates in 2015, with trends from 2000: a systematic analysis
Data produced by the World Health Organization, UNICEF, LSHTM and Johns Hopkins University to estimate national low birthweight (LBW) and numbers for 195 countries. LBW data was collated through a systematic review of national routine/registration systems, nationally representative surveys, and other data sources, and subsequently modelled using restricted maximum likelihood estimation with country-level random effects. Data includes a list of 1447 rate data points used as an input to the modelled estimates, yearly national-level covariates for each of the 195 countries studied from 2000 to 2015, and information on estimated low birthweight rates from 2000 to 2015 for 148 countries with data. Stata code used to generate these estimates is provided
National, regional, and global trends in insufficient physical activity among adults from 2000 to 2022:A pooled analysis of 507 population-based surveys with 5Ā·7 million participants
Background Insufficient physical activity increases the risk of non-communicable diseases, poor physical and cognitivefunction, weight gain, and mental ill-health. Global prevalence of adult insufficient physical activity was last publishedfor 2016, with limited trend data. We aimed to estimate the prevalence of insufficient physical activity for 197 countriesand territories, from 2000 to 2022.Methods We collated physical activity reported by adults (aged ā„18 years) in population-based surveys. Insufficientphysical activity was defined as not doing 150 minutes of moderate-intensity activity, 75 minutes of vigorous-intensityactivity, or an equivalent combination per week. We used a Bayesian hierarchical model to compute estimates ofinsufficient physical activity by country or territory, year, age, and sex. We assessed whether countries or territories,regions, and the world would meet the global target of a 15% relative reduction of the prevalence of insufficientphysical activity by 2030 if 2010ā22 trends continue.Findings We included 507 surveys across 163 countries and territories. The global age-standardised prevalence ofinsufficient physical activity was 31Ā·3% (95% uncertainty interval 28Ā·6ā34Ā·0) in 2022, an increase from 23Ā·4%(21Ā·1ā26Ā·0) in 2000 and 26Ā·4% (24Ā·8ā27Ā·9) in 2010. Prevalence was increasing in 103 (52%) of 197 countries andterritories and six (67%) of nine regions, and was declining in the remainder. Prevalence was 5 percentage pointshigher among female (33Ā·8% [29Ā·9ā37Ā·7]) than male (28Ā·7% [25Ā·0ā32Ā·6]) individuals. Insufficient physical activityincreased in people aged 60 years and older in all regions and both sexes, but age patterns differed for those youngerthan 60 years. If 2010ā22 trends continue, the global target of a 15% relative reduction between 2010 and 2030 will notbe met (posterior probability <0Ā·01); however, two regions, Oceania and sub-Saharan Africa, were on track withconsiderable uncertainty (posterior probabilities 0Ā·70ā0Ā·74).Interpretation Concerted multi-sectoral efforts to reduce insufficient physical activity levels are needed to meet the2030 target. Physical activity promotion should not exacerbate sex, age, or geographical inequalities
Global, regional, and national trends in haemoglobin concentration and prevalence of total and severe anaemia in children and pregnant and non-pregnant women for 1995ā2011: a systematic analysis of population-representative data
Background Low haemoglobin concentrations and anaemia are important risk factors for the health and development
of women and children. We estimated trends in the distributions of haemoglobin concentration and in the prevalence
of anaemia and severe anaemia in young children and pregnant and non-pregnant women between 1995 and 2011.
Methods We obtained data about haemoglobin and anaemia for children aged 6ā59 months and women of
childbearing age (15ā49 years) from 257 population-representative data sources from 107 countries worldwide. We
used health, nutrition, and household surveys; summary statistics from WHOās Vitamin and Mineral Nutrition
Information System; and summary statistics reported by other national and international agencies. We used a
Bayesian hierarchical mixture model to estimate haemoglobin distributions and systematically addressed missing
data, non-linear time trends, and representativeness of data sources. We quantifi ed the uncertainty of our estimates.
Findings Global mean haemoglobin improved slightly between 1995 and 2011, from 125 g/L (95% credibility interval
123ā126) to 126 g/L (124ā128) in non-pregnant women, from 112 g/L (111ā113) to 114 g/L (112ā116) in pregnant
women, and from 109 g/L (107ā111) to 111 g/L (110ā113) in children. Anaemia prevalence decreased from 33% (29ā37)
to 29% (24ā35) in non-pregnant women, from 43% (39ā47) to 38% (34ā43) in pregnant women, and from 47%
(43ā51) to 43% (38ā47) in children. These prevalences translated to 496 million (409ā595 million) non-pregnant
women, 32 million (28ā36 million) pregnant women, and 273 million (242ā304 million) children with anaemia in
2011. In 2011, concentrations of mean haemoglobin were lowest and anaemia prevalence was highest in south Asia
and central and west Africa.
Interpretation Childrenās and womenās haemoglobin statuses improved in some regions where concentrations had
been low in the 1990s, leading to a modest global increase in mean haemoglobin and a reduction in anaemia
prevalence. Further improvements are needed in some regions, particularly south Asia and central and west Africa, to
improve the health of women and children and achieve global targets for reducing anaemia.
Funding Bill & Melinda Gates Foundation, Grand Challenges Canada, and the UK Medical Research Council
Report on the 2013 Rapid Assessment Survey of Marine Species at New England Bays and Harbors
Introduced species (i.e., non-native species that have become established in a new location) have increasingly been recognized as a concern as they have become more prevalent in marine and terrestrial environments (Mooney and Cleland 2001; Simberloff et al. 2005). The ability of introduced species to alter population, community, and ecosystem structure and function, as well as cause significant economic damage is well documented (Carlton 1989, 1996b, 2000; Cohen and Carlton 1995; Cohen et al. 1995; Elton 1958; Meinesz et al. 1993; Occhipinti-Ambrogi and Sheppard 2007; Pimentel et al. 2005; Thresher 2000). The annual economic costs incurred from managing the approximately 50,000 introduced species in the United States alone are estimated to be over $120 billion (Pimentel et al. 2005). Having a monitoring network in place to track new introductions and distributional changes of introduced species is critical for effective management, as these efforts may be more successful when species are detected before they have the chance to become established. A rapid assessment survey is one such method for early detection of introduced species. With rapid assessment surveys, a team of taxonomic experts record and monitor marine speciesāproviding a baseline inventory of native, introduced, and cryptogenic (i.e., unknown origin) species (as defined by Carlton 1996a)āand document range expansions of previously identified species. Since 2000, five rapid assessment surveys have been conducted in New England. These surveys focus on recording species at marinas, which often are in close proximity to transportation vectors (i.e., recreational boats). Species are collected from floating docks and piers because these structures are accessible regardless of the tidal cycle. Another reason for sampling floating docks and other floating structures is that marine introduced species are often found to be more prevalent on artificial surfaces than natural surfaces (Glasby and Connell 2001; Paulay et al. 2002). The primary objectives of these surveys are to: (1) identify native, introduced, and cryptogenic marine species, (2) expand on data collected in past surveys, (3) assess the introduction status and range extensions of documented introduced species, and (4) detect new introductions. This report presents the introduced, cryptogenic, and native species recorded during the 2013 survey
Estimates of burden and consequences of infants born small for gestational age in low and middle income countries with INTERGROWTH-21st standard: analysis of CHERG datasets
Objectives: To estimate small for gestational age birth prevalence and attributable neonatal mortality in low and middle income countries with the INTERGROWTH-21st birth weight standard.Design: Secondary analysis of data from the Child Health Epidemiology Reference Group (CHERG), including 14 birth cohorts with gestational age, birth weight, and neonatal follow-up. Small for gestational age was defined as infants weighing less than the 10th centile birth weight for gestational age and sex with the multiethnic, INTERGROWTH-21st birth weight standard. Prevalence of small for gestational age and neonatal mortality risk ratios were calculated and pooled among these datasets at the regional level. With available national level data, prevalence of small for gestational age and population attributable fractions of neonatal mortality attributable to small for gestational age were estimated.Setting: CHERG birth cohorts from 14 population based sites in low and middle income countries.Main outcome measures: In low and middle income countries in the year 2012, the number and proportion of infants born small for gestational age; number and proportion of neonatal deaths attributable to small for gestational age; the number and proportion of neonatal deaths that could be prevented by reducing the prevalence of small for gestational age to 10%.Results: In 2012, an estimated 23.3 million infants (uncertainty range 17.6 to 31.9; 19.3% of live births) were born small for gestational age in low and middle income countries. Among these, 11.2 million (0.8 to 15.8) were term and not low birth weight (ā„2500 g), 10.7 million (7.6 to 15.0) were term and low birth weight (\u3c2500 \u3eg) and 1.5 million (0.9 to 2.6) were preterm. In low and middle income countries, an estimated 606ā500 (495ā000 to 773ā000) neonatal deaths were attributable to infants born small for gestational age, 21.9% of all neonatal deaths. The largest burden was in South Asia, where the prevalence was the highest (34%); about 26% of neonatal deaths were attributable to infants born small for gestational age. Reduction of the prevalence of small for gestational age from 19.3% to 10.0% in these countries could reduce neonatal deaths by 9.2% (254ā600 neonatal deaths; 164ā800 to 449ā700).Conclusions: In low and middle income countries, about one in five infants are born small for gestational age, and one in four neonatal deaths are among such infants. Increased efforts are required to improve the quality of care for and survival of these high risk infants in low and middle income countries
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