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PubMed1996

The transmission dynamics and control of hepatitis B virus in The Gambia.

A deterministic, compartmental, mathematical model is used to describe the transmission dynamics of hepatitis B virus (HBV) in a high endemicity country. All three major transmission routes are included in the model, that is, perinatal, horizontal and sexual transmission. The model also reflects the demography of a typical developing country, and incorporates age-dependence in the rates of transmission and the probability of becoming a chronic carrier. Numerical simulations of the model are shown to capture the observed age-specific patterns of serological markers. The sensitivity of the model to age-specific heterogeneities and routes of transmission is investigated. The model is used in a preliminary study of the possible implications of mass infant immunization on HBV epidemiology, and the results suggest that eradication of HBV may be achieved by immunizing less than 70 per cent infants, which is relatively low compared to most childhood viral infections. This is due in part to the interaction between changes to the average age at infection under immunization, and the nature of age-dependence in the force of infection and the probability of becoming a carrier. However, numerical results also suggest that eradication may take many decades to be achieved, largely due to the presence of a pool of chronic carriers. Furthermore, there may be a significant lag between the implementation of mass infant immunization and a decline in the incidence of liver cancer.

Adolescent↗
PubMed1998

The influence of practice characteristics on the prescribing of benzodiazepines and appetite suppressant drugs.

BACKGROUND: The prescribing volume of benzodiazepines and of appetite suppressant drugs have been suggested as possible indicators of prescribing quality. OBJECTIVE: To investigate the variation among general practices in the prescribing of benzodiazepines and appetite suppressants by examining the contribution to this variation of training status, partnership status, fundholding status and the level of deprivation in the practice population. METHODS: Prescribing data (PACT) were analysed for 350 practices in the former Mersey Regional Health Authority, for the year ending March 1991 and the year ending March 1994. Data were first standardized for variation in practice population demography. Multiple linear regressions were used to investigate the variation among practices in standardized prescribing volume in both years. RESULTS: For benzodiazepines, training status and partnership status contributed to all models and level of deprivation contributed to some (percentage of variation explained for year ending March 1991: 10% to 21%, year ending March 1994: 8% to 20%). For appetite suppressant drugs fundholding status and an interaction between training status and level of deprivation contributed to all models in both years (percentage of variation explained for year ending March 1991: 19% to 20%, year ending March 1994: 20% to 21%). CONCLUSION: The prescribing of benzodiazepines is lower in training practices, in multi-partner practices and in practices serving a less deprived population, while the prescribing of appetite suppressant drugs is lower in training practices and in fundholding practices. Variation in prescribing knowledge, organizational and management capabilities and patient demand may be explanatory factors.

Journal Article↗
PubMed1998

The use of angiotensin converting enzyme inhibitors in general practice--appropriate or inappropriate?

AIMS: To evaluate the pattern of prescribing of angiotensin-converting enzyme (ACE) inhibitors in general practice, related to the primary clinical diagnosis and concomitant medication. DESIGN: A descriptive survey of general practitioners' prescribing habits, presumptive diagnosis and patient demography over a period of 2 weeks in April 1994. SETTING: A stratified quota sample of 22 practices in Northern Ireland. RESULTS: The major clinical indication for the use of ACE inhibitors was essential hypertension (61.5%) with only a minority usage (19.9%) in congestive heart failure. Co-prescription of drugs with potential for interaction with angiotensin-converting enzyme inhibitors was not uncommon (16.7%). Of the 353 patients with a diagnosis of congestive heart failure, only 64 (18.1%) were receiving ACE inhibitors. The dosages used were lower than recommended for this indication. A significantly higher proportion of elderly patients with heart failure were prescribed hypnotic drugs (14.7% versus 8.3%; p<0.001) and had the co-existence of insomnia (11.8% versus 6.9%; p<0.001) compared to patients without heart failure. CONCLUSIONS: ACE inhibitors were underused in the treatment of congestive heart failure, and were often prescribed in suboptimal dosages. The frequent concurrent prescription of hypnotics and the co-existence of insomnia in heart failure may reflect this therapeutic strategy.

Journal Article↗
PubMed1999

The association of some practice characteristics with antibiotic prescribing.

BACKGROUND: Antibiotic prescribing in general practice is often considered inappropriate, and its volume excessive. Considerable variation in antibiotic prescribing volume and costs exists among practices. OBJECTIVE: To investigate some factors behind the variation in antibiotic prescribing among general practices, by examining the contribution to this variation of the level of deprivation in the practice population, training status, partnership status, and fundholding status. METHOD: Analysis of prescribing data (PACT) from 351 practices in the Mersey region for the year ending March 1991 and the year ending March 1994; prescribing data standardized for variation in practice population demography. Use of multiple linear regressions to investigate the variation among practices in standardized prescribing volume and standardized prescribing costs, in both years. RESULTS: Level of deprivation, training status and partnership status contributed to the models explaining variation in prescribing volume. The same variables contributed to the model explaining variation in prescribing costs in the year ending March 1991. For the year ending March 1994, level of deprivation, training status, and fundholding status contributed to all models. CONCLUSION: Higher levels of antibiotic prescribing occur in practices serving more deprived communities, in single-handed practices, and in non-training practices. These higher levels of prescribing may be due to higher levels of morbidity, but may also reflect the organization and attitudes of these practices.

Journal Article↗
PubMed2000

mtDNA lineage analyses: origins and migrations of Micronesians and Polynesians.

The islands of Micronesia and Polynesia collectively comprise the last major region of the globe to be settled by humans. Both of these groups of islands were colonized within the last 4,000 years by Austronesian-speaking agriculturists. Based on biogeographic and linguistic patterns, central-eastern Micronesia and Polynesia are included by many in a single category called Remote Oceania. Similarities of biologic, linguistic, and cultural traits within Remote Oceania highlight a question central to Oceanic studies: Are similarities among islands due to a common origin of isolated communities, to ongoing interactions among islands, or both? Analyses of mitochondrial DNA (mtDNA) sequences reveal that most remote Oceanic populations are polyphyletic. These polyphyletic populations violate the assumptions of many genetic distance and population demography models and so are problematic to interpret. The majority of mtDNA sequences from Micronesian and Polynesian populations are derived from Asia, whereas others are inferred to have originated in New Guinea. These data support an Island Southeast Asian origin and a colonization route along the north coast of New Guinea. The Marianas and Yap proper (main island) appear to have been independently settled directly from Island Southeast Asia, and both have received migrants from Central-Eastern Micronesia since then. Palau clearly demonstrates a complex prehistory including a significant influx of lineages from New Guinea. Thus genetic similarities among Micronesian and Polynesian populations result, in some cases, from a common origin, and in others, from extensive gene flow.

DNA, Mitochondrial↗
PubMed1982

Studies in prognostic factors relating to chemotherapy for advanced gastric cancer.

The prognostic value of pretreatment information relating to prior treatment, demography, physical status, symptoms, disease involvement, pathologic, immunologic, and clinical chemistries were analyzed for a series of 322 patients with advanced gastric cancer. All patients received chemotherapy upon entry into Gastrointestinal Tumor Study Group protocols which were active between 1975 and 1978. Multivariate models were used to study relationships between prognostic factors and survival for all patients and objective tumor resonse for a subset of 137 patients with measurable disease. The initial performance status was a leading determinant of survival (P less than 0.0001). In addition, new summary measures relating to blood chemistries (P less than 0.01) and differential counts (P less than 0.001) were shown to influence patient survival. Blood chemistry parameters included SGOT, total serum protein, and total direct bilirubin while differential counts included absolute granulocytes, lymphocytes, and monocytes. Thus, the initial performance status, measurable disease status, blood chemistries, and differential counts are recommended as stratification factors in the design and analysis of trials involving patients with advanced gastric cancer. The initial performance status was examined in relation to other pretreatment data. The performance status at study entry correlated independently with the degree of weight loss (P less than 0.001), blood chemistries (P less than 0.01), differential counts (P less than 0.05), and peritoneal metastases (P less than 0.05). The measurable and nonmeasurable subgroups were compared with respect to baseline characteristics. Patients with measurable disease had more liver metastases (56 versus 35%) and less peritoneal metastases (76 versus 49%) than patients with nonmeasurable disease. Controlling for the imbalance in liver and peritoneal metastases, the presence of measurable disease was less favorable than nonmeasurable disease with respect to survival. Regarding the pathways of disease spread, there was a strong correlation (P less than 0.001) between primary tumor site within the stomach and location of metastases. Diffuse lesions were associated with the lowest frequency (25%) of liver metastases. Diffuse lesions (58%) and tumors of the pyloris (54%) were associated with the highest percentage of peritoneal metastases. Tumors of the cardia or fundus were more likely to metastasize to the liver while diffuse tumors were more likely to spread to the peritoneum. Pretreatment factors under study did not appear to be the dominant factors responsible for prolongation of survival in patients with an objective tumor response. Pretreatment factors predicted a three week advantage; however, a 22 week advantage was observed for responders over nonresponders.

Adenocarcinoma↗
PubMed1988

Trends in smoking, cancer risk, and cigarette promotion. Current priorities for reducing tobacco exposure.

Tobacco use in the US is currently responsible for more than 30% of all cancer deaths, including cancers of the lung, larynx, oral cavity, pharynx, pancreas, kidney, bladder, and cervix. The lung cancer epidemic in men and then women since the turn of the century followed an increased prevalence of cigarette smoking. Recent declines in lung cancer rates in men reflect a decline in men's smoking prevalence over the past few decades. However, lung cancer is still the major cause of cancer death in men and is now essentially tied with breast cancer as the leading cause of cancer death in women. The demography of smoking has markedly altered over time, so that current efforts to prevent tobacco use should address young women, ethnic minorities, lower socioeconomic groups, and Third World populations. The tobacco industry's aggressive strategies to promote tobacco use should also be monitored, publicized, and countered. Relevant activities for the individual health-care practitioner are suggested here. Because more than 25% of Americans are still smoking, our priority in cancer prevention must be to continually encourage the reduction of tobacco use.

Adolescent↗
PubMed1996

Interpreting genetic variability: the effects of shared evolutionary history.

Data from different individuals at a single locus are positively correlated because of the shared genealogy of the sampled genes. This paper illustrates the qualitative effects on genealogical trees of assumptions about population demography, and it considers the consequences for genetic variability. An understanding of these effects is invaluable in the interpretation of data and for inferences about population history. In contrast, traditional genetic measures of diversity and approximation methods do not seem well suited for addressing the problem.

Animals↗
PubMed1997

Relationship-specific social psychological adaptations.

Mainstream social psychology has sought parsimonious explanations of broad general applicability, and has in practice focused on stranger interactions. An evolutionary perspective; however, justifies predicting a rich diversity of relationship-specific social psychological adaptations. The demands of motherhood, fatherhood, mateship, sibship and other relationships are qualitatively distinct, and so, it appears, are the psychophysiological mechanisms that have evolved to deal with them. One window on what distinguishes social relationships is provided by the substance and epidemiology of interpersonal conflicts. Homicides exhibit victim-killer relationship-specific patterns in context, motive and demography, which we discovered only because we adopted an evolutionary psychological perspective. We offer a number of specific hypotheses about possible human psychological adaptations that have yet to be assessed, but are readily derived from consideration of the particular qualities of specific relationship types.

Adaptation, Psychological↗
PubMed2002

Rapid confirmation of Southeast Asian and Filipino alpha-thalassemia genotypes from newborn screening specimens.

Alpha(+)-thalassemia (-alpha) is prevalent throughout tropical and subtropical regions of world, whereas alpha(0)-thalassemia (--) occurs at higher frequency in Southeast Asia. Homozygosity for the alpha(0)-thalassemia deletion (--/--) is a serious health problem in Southeast Asia and the Philippines and is responsible for the majority of hydrops fetalis in this region. Asian immigration in United States has impacted the demography of genetic disease in U.S. As Asians comprise of 10% of all California births and represent a population at highest risk for alpha(0)-thalassemia, we developed a rapid and efficient PCR approach to detect the common alpha(0)-thalassemia deletions in Southeast Asians and Filipinos using newborn screening specimen.

Asia, Southeastern↗
PubMedDate not supplied

Fetal programming: adaptive life-history tactics or making the best of a bad start?

Fetal programming is an ontogenetic phenomenon of increasing interest to human biologists. Because the downstream consequences of fetal programming have clear impacts on specific life-history traits (e.g., age at first reproduction and the general age-pattern of reproductive investments), a number of authors have raised the question of the adaptive significance of fetal programming. In this paper, I review in some detail several classical models in life-history theory and discuss their relative merits and weaknesses for human biology. I suggest that an adequate model of human life-history evolution must account for the highly structured nature of the human life cycle, with its late age at first reproduction, large degree of iteroparity, highly overlapping generations, and extensive, post-weaning parental investment. I further suggest that an understanding of stochastic demography is essential for answering the question of the adaptive significance of fetal programming, and specifically the finding of low birth weight on smaller adult body size and earlier age at first reproduction. Using a stage-structured stochastic population model, I show that the downstream consequences of early deprivation may be "making the best of a bad start" rather than an adaptation per se. When a high-investment strategy entails survival costs, the alternate strategy of early reproduction with relatively low investment may have higher fitness than trying to play the high-investment strategy and failing.

Adaptation, Physiological↗
PubMed2005

Mapping genes of complex psychiatric diseases in Daghestan genetic isolates.

Genetic isolates, which provide outstanding opportunities for identification of susceptibility genes for complex diseases, can be classified as primary (having an ancient demographic history in a stable environment) or secondary (having a younger demographic history) Neel [1992: Minority populations: Genetics, demography, and health, pp. 1-13]. Daghestan contains 26 out of 50 indigenous Caucasus ethnicities that have been in existence for hundreds of generations in the same highland region. The ethnic groups are subdivided into numerous primary isolates. The founder effect and gene drift in these primary isolates may have caused aggregation of specific haplotypes with limited numbers of pathogenic alleles and loci in some isolates relative to others. These are expressed as inter-population differences in lifetime prevalence and features of certain complex clinical phenotypes and in patterns of genetic linkage and linkage disequilibrium (LD). Stable highland and ethnic-cultural environments have led to increased penetrance and a reduced number of phenocopies, which typically hamper the identification of any susceptibility genes for complex diseases. Owing to these characteristics of the primary isolates, a comparative linkage study in the primary isolates allows us to define the number of susceptibility genes for any complex disease and to identify the source of variability and non-replication of linkage analysis results. As part of an ongoing study, seven extended schizophrenia and one nonspecific mental retardation kindreds have been ascertained from Daghestan isolates. Lifetime morbid risk for schizophrenia in the isolates varied from 0 to 5%. A genome scan with markers spaced 10 cM apart was carried out on these pedigrees and linkage analysis was performed using descent graph methods, as implemented in Simwalk2. To identify regions containing susceptibility genes within these kindreds, we followed up those regions with non-parametric and parametric linkage analyses, with the choice of genetic model guided by the results obtained in the NPL. While the analyses are ongoing, the most positive findings were made in different isolated pedigrees on chromosomes 17p11, 3q24, and 22q for schizophrenia and on chromosome 12q for nonspecific mental retardation.

Chromosome Mapping↗
PubMed2006

Human culture and monkey behavior: Assessing the contexts of potential pathogen transmission between macaques and humans.

An in-depth understanding of the contexts and patterns of human-macaque interactions can play an important role in assessing and managing the potential for pathogen transmission. The Padangtegal Monkey Forest in Bali, Indonesia, and the Upper Rock Nature Reserve in Gibraltar are two sites that have been relatively well studied in regard to human-macaque interactions. This article presents an overview of interaction patterns between humans and macaques at these sites along with a description of the cultural, demographic, and contextual differences between local and nonlocal humans at the sites. Differences in these two sites' interaction patterns included bite rates, the role of food in aggressive interactions, and the context in which the interactions took place. Similarities included overrepresentation by adult male macaques in interactions and a substantial impact by local cultural and demographic factors. These similarities and differences are interpreted as resulting from differences in macaque species and behaviors, and human demography, culture, and behavioral patterns.

Adolescent↗
PubMed1981

History and development of paleopathology.

In the nineteenth century, accurate descriptive studies, often dealing with pre-Columbian "syphilis," were made by Virchow, J. Jones, and Putnam. Hrdlicka, Moodie, Ruffer, and others in the early twentieth century carried out research on subjects ranging from trephination to schistosomiasis. However, it was not until Hooton, Williams, Stewart, Wells, and others (1930 to 1965) that paleopathology was combined with paleodemography to get a population perspective on health as an equilibrium with disease. Not until recently, with the creative summaries of Jarcho and Brothwell, have we had bone pathologists (Lent Johnson and especially Putschar) and others (Moseley in blood, Cockburn and Allison in epidemiology and mummies) working actively with physical anthropologists and historians. This cooperation has triggered a major revival in the study of bone physiology and responses to disease (Ortner), disease ecology, demography and health, and paleonutrition (Goldstein, Laughlin, Cook and Buikstra, Ubelaker, Angel). New techniques range from histology to immunochemistry and now involve a host of young investigators.

History, 20th Century↗
PubMed1982

Osteology of a slave burial population from Barbados, West Indies.

A unique seventeenth-nineteenth century slave cemetery population from Newton plantation, Barbados, allows examination of craniodental characters in relation to ethnohistorical data. Age-at-death estimates suggest life expectancy at birth of 29 years and low infant mortality; historical demography, however, suggests life expectancy of 20 years and very high infant mortality. Tooth decay, bilateral tooth loss, periodontal disease, root hypercementosis, and severe enamel hypoplasia are high in frequency. The teeth yield evidence of such cultural practices as pipe-smoking and incisor mutilation. Several skeletal features reflect periodic near-starvation. Directional and fluctuating dental asymmetry, relative tooth size, and hypoplasia distribution suggest slaves experienced considerable weaning trauma; metabolic stress at this time exceeded that of prenatal and immediate postnatal periods. Odontometrics and dental and cranial nonmetric traits indicate that modern Blacks are intermediate between the ancestral slaves and modern Whites but more similar to the latter, suggesting effects of environmental covariance exceed those of genetic admixture. Nonmetric trait distributions show nonrandom patterns according to area of burial in the cemetery, a possible result of family segregation.

Adolescent↗
PubMed1986

Genetic and environmental effects on growth of children from a subsistence agricultural community in southern Mexico.

Sibling correlations for size attained in height, weight, sitting height, estimated leg length, the triceps skinfold, arm circumference, and estimated midarm muscle circumference were compared in 6- through 13-year-old schoolchildren grouped by household socioeconomic status. The children were residents of a Zapotec-speaking, subsistence agricultural community in the Valley of Oaxaca in southern Mexico. Sibling pairs were classified as being from high and low socioeconomic status (SES) households, and sibling correlations were computed within each SES group controlling for environmental effects derived from a factor analysis of information on household demography and land and livestock holdings. Like-sex siblings from lower SES households have significantly different correlations in four instances. Correlations are higher for leg length in lower SES brothers and higher for sitting height and weight in lower SES sisters, while the correlation for sitting height is higher in upper SES brothers. The sibling correlation results are not entirely consistent with observations on growth status by SES, particularly if the power and similarity of a common environment is the only cause of higher sibling correlations. Reduced body size under poorer socioeconomic and presumably nutritional circumstances is apparent, but it is not possible in this analysis to distinguish whether genotypic (developmental) plasticity or genetic adaptation, or both, are involved.

Adolescent↗
PubMed1987

The age-sex structure of the slave population in Harris County, Texas: 1850 and 1860.

The effect of the slave system on demography can be revealed by examining the age-sex structure of slave populations. The age-sex structure of slaves in Harris County, Texas is investigated using the 1850 and 1860 slave schedules. Median ages for black and mulatto slaves suggest that the population was young. Population pyramids exhibit a narrow base and top with a broad middle. The high proportion of slaves between 10 and 30 years of age and the increase in population size between 1850 and 1860 were mainly related to the importation of slaves and only partly due to natural increase. The data also show that black slaves were older on small plantations while mulattoes were older on larger farms. It is suggested that differential treatment in terms of purchase practices, assignment of tasks, food allocation, and/or differential susceptibility to infectious diseases may account for this pattern.

Black or African American↗
PubMed1990

Heterogeneity of the blood pressure distribution among Solomon Islands societies with increasing acculturation.

This study illustrates the very complex nature of gene by environmental interactions influencing the blood pressure (BP) distribution in a series of genetically distinctive populations undergoing rapid acculturation. We report the results of two BP and anthropometric surveys on Solomon Islands societies separated by an interval of 14 to 19 years. While differences in acculturation existed at the time of the initial survey, the interval between surveys was marked by rapid acculturation in almost all societies. Seven of the eight societies originally covered were included in the resurvey, and a large but variable proportion of the original sample subjects was recovered in the follow-up. Because the genetic relationships of the societies have been described, we were able to establish the following points concerning the role of genetic differences in determining the distribution of BP among these populations and, more important, the interaction of these genetic differences with changes associated with increasing acculturation: 1) In the initial survey, mean adjusted systolic and diastolic BPs were significantly heterogeneous among societies within and among genetically related clusters of societies (genetic clusters) and sexes. At the same time, rank differences in these means were not associated with rank differences in acculturation status among societies ignoring cluster membership. 2) Importantly, in the follow-up survey increasing acculturation resulted in the disappearance of significant differences in mean systolic and diastolic BP among genetic clusters in males, despite continued significant heterogeneity among societies within genetic clusters. In females, differences among genetic clusters persisted, but the degree of significance was substantially less with increasing acculturation. We interpret these changes as evidence for genotype by environment interaction. 3) There were significant differences in interindividual variances of both systolic and diastolic BPs among genetic clusters in the first survey. Ranks of these variances were not significantly associated with acculturation rank. In the follow-up survey, however, most societies showed striking increases in the variance of both systolic and diastolic BPs with increased acculturation. These increases in variance of both systolic and diastolic BPs may be related to a) shifts in demography and/or anthropometry of some societies; b) increased range and intensity of environmental factors affecting BP and associated with increased acculturation; and/or c) genotype by environmental interactions. 4) The correlation between systolic and diastolic BP decreased over the interval for all societies within and among genetic clusters. This trend was partly the result of larger changes in variances for systolic than diastolic BP in the resurveys.(ABSTRACT TRUNCATED AT 400 WORDS)

Acculturation↗