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PubMed2006

Positive selection versus demography: evolutionary inferences based on an unusual haplotype structure in Drosophila simulans.

Coalescent simulations were used to investigate the possible role of population subdivision and history in shaping nucleotide variation in a recombining 88-kb genomic fragment of Drosophila simulans displaying an unusual large-scale haplotype structure. The multilocus analysis, based on summary statistics using specific demographic null models under recombination, indicates that the observed levels of linkage disequilibrium differed significantly from the values expected under different bottleneck and population admixture scenarios. These results indicate that demography alone may not account for the observed pattern of variation and support the previous claim that the data are better described by a model in which an adaptive mutation has not yet gone to fixation.

Animals↗
PubMed2004

Demography of paediatric renal care in Europe: organization and delivery.

BACKGROUND: Members of the European Society of Paediatric Nephrology (ESPN) initiated a study of the demography and policy of paediatric renal care among European countries at the end of the 20th century. METHODS: A questionnaire was mailed to the presidents of each of 43 national renal paediatric societies or working groups in Europe. Data on each country's population, income as reflected by its gross national product and infant mortality rate, were obtained from the United Nations. The paediatric health care systems were previously divided into three types: general practitioner care system, paediatric care system and combined care system (CCS). RESULTS: In 1998, 842 specialized paediatric nephrologists worked in hospitals in 42 European countries. The median number of paediatric nephrologists per million child population (pmcp) was 4.9 (range 0-15). The median number of children served per paediatric nephrologist was significantly higher in countries with the general practitioner care system than in those with the paediatric or combined care system (CCS), namely 370 747 vs 169 456 and 191 788, respectively. In addition to specially trained paediatric nephrologists, there were 1087 paediatricians with a part-time interest/activity in paediatric nephrology in hospitals in 34 European countries. Eastern European countries had significantly more general paediatricians with part-time nephrological activities than countries belonging to the European Union (EU), 16.7 vs 6.6 pmcp. In 1998, 92% of 42 European countries offered paediatric dialysis facilities for acute renal failure and 90% for chronic renal failure and 55% offered paediatric renal transplantation (RTx). Only 30% of Eastern European countries (central omitted) offered paediatric RTx vs 87% of EU countries. The availability of paediatric RTx was associated significantly with the countries' gross national product (r = 0.53, P<0.001). The median number of paediatric hospitals offering dialysis for childhood chronic renal failure was 1.5 pmcp (range 0-5.0) and the median number of paediatric hospitals offering paediatric RTx was 0.4 pmcp (range 0-3.5). Fewer children were on dialysis or were transplanted in Eastern European countries than in the EU. CONCLUSIONS: At the end of the 20th century, there was a marked variation in delivery of paediatric renal care within Europe. This was related to factors such as size of the population, geographical and political situation, the type of primary paediatric care system and economic situation. European countries were far from equal with regard to access of renal replacement therapy for children. Improvement of the economic situation is beyond the capabilities of paediatric nephrologists. However, in these days of world-wide globalization paediatricians in greater Europe should be able to achieve better cooperation and exchange of ideas and information which would be the first step towards equality of renal care for children.

Adolescent↗
PubMed1996

Statistical modelling reveals demography and time are the main contributing factors in global sperm count changes between 1938 and 1996.

Declining sperm count reports have caused enormous concern to both the scientific community and to society. We reproduced the linear regression analysis and the quadratic model analysis using the 50 year sperm count data published in Carlsen's report and found that neither model adequately described the data. The reported decline in sperm count could be due to observational bias and overinterpretation of linear regression. In fact only 36% of the total variability in sperm count was explained by the linear model and 42% by the quadratic model. The linear model was no longer valid when three new European reports on sperm counts were included in the analysis. The quadratic model, however, suggested an upward trend of sperm count after 1975 (R2 = 0.48, P < 0.0001). Factors other than the 'passage of time' may have contributed to the initial decline of sperm count. An immediate candidate was demography. Our analysis showed that sperm counts in USA were significantly higher in 1938-1956 compared with those in 1957-1974 and 1975-1988, but not in the European or Asian/African/South American countries. The variability of the USA sperm count (1938-1988) explained by the linear and quadratic models was found to be 71 and 70% respectively. The quadratic model importantly indicated that the sperm count in USA decreases asymptotically towards a limiting value and global sperm counts could be increasing since 1970. The non-uniform nature of the global sperm count change suggested that local variations in pollution, diet but not global warming were important determinants of reproductive health.

Demography↗
PubMed1989

Vital statistics, demography, and schizophrenia: editor's introduction.

The Guest Editor introduces this Theme Issue of the Schizophrenia Bulletin with an overview of the kinds of subject matters appropriate for a comprehensive understanding of the vital statistics and demography relating to schizophrenia and schizophrenic patients--births, deaths, marriages, divorces, fertility, age, sex, race, occupation, place of residence, season of birth, class mobility, homelessness, criminality, industrialization, and suicide. Major sources of the statistics relating to schizophrenia are listed. He calls for a national case register and the use of a unique identifier with linkage across data bases in various branches of government so as to inform a descriptive as well as an experimental (hypothesis-testing) epidemiology.

Cross-Sectional Studies↗
PubMed2006

Complex population dynamics and complex causation: devils, details and demography.

Population dynamics result from the interplay of density-independent and density-dependent processes. Understanding this interplay is important, especially for being able to predict near-term population trajectories for management. In recent years, the study of model systems-experimental, observational and theoretical-has shed considerable light on the way that the both density-dependent and -independent aspects of the environment affect population dynamics via impacting on the organism's life history and therefore demography. These model-based approaches suggest that (i) individuals in different states differ in their demographic performance, (ii) these differences generate structure that can fluctuate independently of current total population size and so can influence the dynamics in important ways, (iii) individuals are strongly affected by both current and past environments, even when the past environments may be in previous generations and (iv) dynamics are typically complex and transient due to environmental noise perturbing complex population structures. For understanding population dynamics of any given system, we suggest that 'the devil is in the detail'. Experimental dissection of empirical systems is providing important insights into the details of the drivers of demographic responses and therefore dynamics and should also stimulate theory that incorporates relevant biological mechanism.

Adaptation, Physiological↗
PubMed2004

Population biology of the invasive freshwater snail Physa acuta approached through genetic markers, ecological characterization and demography.

Abstract The respective role of factors acting on population functioning can be inferred from a variety of approaches, including population genetics and demography. We here investigated the role of four of these factors (mating systems, population size, bottlenecks and migration) in the hermaphroditic freshwater snail Physa acuta. Twenty-four populations were sampled either around Montpellier (local scale), or at the scale of France (global scale). At local scale, eight populations were sampled twice, before and after summer drying out. The genetic structure of these populations was studied using microsatellite loci. Populations were classified according to openness (ponds vs. rivers) and water regime (permanent vs. temporary) allowing predictions on genetic patterns (e.g. diversity within populations and differentiation). At local scale, progeny-arrays analysis of the selfing rate was conducted, and size distributions of individuals were followed over two years. Results with regard to the four factors mentioned above were: (i) Estimates of population selfing rates derived from inbreeding coefficients were only slightly higher than those from progeny-arrays. (ii) More variation was detected in rivers than in ponds, but no influence of water regime was detected. One reason might be that permanent populations are not going less often through low densities than those from temporary habitats at the time scale studied. (iii) There was limited evidence for genetic bottlenecks which is compatible with the fact that even marked reduction in water availability was not necessarily associated with demographic bottlenecks. More generally, bottlenecks reducing genetic variation probably occur at population foundation. (iv) Lower genetic differentiation was detected among rivers than among ponds which might be related to limitations on gene flow. Demographic and temporal genetic data further indicates that flooding in rivers is unlikely to induce marked gene flow explaining the strong genetic differentiation at short geographical scale in such habitats. Finally, the demographic data suggest that some populations are transitory and subject to recurrent recolonization, a pattern that was also detected through genetic data.

Animals↗
PubMed2004

Genetic structure, phylogeography and demography of two ground-beetle species endemic to the Tenerife laurel forest (Canary Islands).

The volcanic island of Tenerife (Canary archipelago) was formerly covered at 600-1200 m above sea level on most of its northern side by a cloud forest holding much of the endemic insect fauna. In the most significant surviving patches of this laurel forest at the eastern and western tips of the island occur two forest-specialist, closely related species of Eutrichopus (Coleoptera, Carabidae); here we present data on mitochondrial DNA variation among populations of these species. In total, 116 individuals from 16 localities were sampled and a 638 bp fragment of the cytochrome oxidase subunit II gene was sequenced, obtaining evidence for two distinct evolutionary lineages, in accordance with morphological and biogeographical data. Volcanic events at approximately 0.7 Ma might be responsible for vicariance and the fragmentation of the geographical range of an ancestral species, causing the establishment of two matrilineal lineages. Using nested clade and historical demography analyses we infer past cycles of demographic bottlenecks followed by population expansion, mostly in agreement with the geological time scale of volcanic events. Recent trends, however, refer to fragmentation of the cloud forest due to human intervention.

Animals↗
PubMed2005

Effects of Holocene climate change on the historical demography of migrating sharp-shinned hawks (Accipiter striatus velox) in North America.

DNA sequences of the mitochondrial control region were analysed from 298 individual sharp-shinned hawks (Accipiter striatus velox) sampled at 12 different migration study sites across North America. The control region proved to be an appropriate genetic marker for identification of continental-scale population genetic structure and for determining the historical demography of population units. These data suggest that sharp-shinned hawks sampled at migration sites in North America are divided into distinct eastern and western groups. The eastern group appears to have recently expanded in response to the retreat of glacial ice at the end of the last glacial maximum. The western group appears to have been strongly effected by the Holocene Hypsithermal dry period, with molecular evidence indicating the most recent expansion following this mid-Holocene climatic event 7000-5000 years before present.

Animals↗
PubMed1987

Forms of migration and measurement in social demography.

"This paper is an attempt to identify the various forms of migration in demography and the associated measurements adopted and their limitation. In trying to conceptualize migration, we are in fact trying to identify those who move or migrants and those who do not move or non-migrants. Further it also involves a place or origin from where the migration starts and a place of destination where it culminates." The author discusses five aspects of territorial mobility, namely, space, residence, time, activity changes, and individual and family criteria. (SUMMARY IN FRE AND SPA)

Demography↗
PubMed1983

Demography and old age.

Demography is of great importance for those involved in caring for the elderly or in planning services. In this paper, current and future variations in the proportions of elderly people around the world are reviewed. The determinants of age structure are considered, and aging and aged populations are defined and discussed. The consequences of population aging extend into every sphere of life; particular attention is paid to the health service and economic implications. Attitudes to population aging and some of the special characteristics of the elderly in the West today are also considered. The paper concludes with a discussion of probable future trends in both the developed and the less developed parts of the world.

Adolescent↗
PubMed2001

Bridging epidemiology and demography: theories and themes.

Epidemiology and demography, although both encumbering several theoretical constructs, are generally applied, problem-solving disciplines concerned with the nature and trajectories of defined groups. There are differences between the two disciplines in substantive interests and methodological traditions, however both have comprehensive perspectives and both are deeply concerned with the health, social, and economic well-being of human populations. One way to promote productive interdisciplinary research is to apply or develop scientific theories that exploit the complementary interests and methods of the two disciplines. Several candidate theories and themes are suggested here, including (1) the life course approach as applied to the biology of longevity; (2) the "modernized" Malthusian dilemma; (3) the demographic transition within developing countries; (4) the theory of evolution and its social and biological implications; (5) reciprocal effects of ecological and environmental characteristics on population health and well-being; and (6) systems theory as an approach to population complexity. Other approaches to fostering interdisciplinary investigation between these disciplines include joint course work, specifically targeted research funding initiatives and collaborative development of new population theory. The latter may be particularly important from several perspectives: uniting disciplines to jointly approach common and important scientific problems, providing existing frameworks with which to generate new scientific questions, and promoting enhanced scientific rigor by more tightly linking methods with hypotheses.

Biological Evolution↗
PubMed2001

Advocacy in epidemiology and demography.

This paper is a summary of a panel discussion at the Conference on Epidemiology and Demography held at Georgetown University, in Washington D.C. on February 8-9, 2001. The participants were Al Hermalin, Linda Martin, Mike Stoto, Robert Wallace, Douglas Weed, and Rose Li (who chaired the session). A list of questions similar to the section headings in this paper was prepared in advance of the conference, and each of the participants was asked to address specific issues, although the presentations typically covered a range of topics. This summary also includes comments from the floor.

Consumer Advocacy↗
PubMed2000

Demography and dog-human relationships of the dog population in Zimbabwean communal lands.

Dogs are Zimbabwe's primary vector for rabies, and the majority live in communal lands (traditional agropastoralist rural areas). In 1994, a household questionnaire survey was conducted to provide baseline data on the demography and dog-human relationships of the dogs in the communal lands. The survey showed that all the dogs were owned, and there was no evidence of a feral population. They were unrestricted and semi-dependent on people. The numbers of dogs per capita varied little in each communal land, resulting in higher dog densities in communal lands with higher human densities, and indicating that people were not intolerant of dogs at higher densities. The population turnover was rapid: the life expectancy of the dogs was 1.1 years, the mean age 2.0 years, and 71.8 per cent died in their first year. The population was heavily skewed towards juveniles, with 40.8 per cent aged less than 12 months. Despite the high juvenile mortality, the population was growing by 6.52 per cent per annum. It was estimated that in 1994 there were 1.36 million dogs in communal lands.

Animals↗
PubMed1998

Demography, symptomatology, and course of disease in ambulatory zoster patients. A physician-based survey in Germany.

This survey summarises the observations of physicians who prospectively recorded clinically relevant data on their patients with an episode of herpes zoster. These included demography of patients, signs and symptoms during the prodromal phase, relevant history, description of disease at the first visit, therapeutic measures and description of disease, and occurrence of postherpetic neuralgia (pain 4-5 weeks after crusting) at the second visit. A total of 2,063 patients were reported to the data management centre. The age distribution resembles that reported in the literature including the notable increase in zoster frequency with advancing age. Almost 20% of the patients, however, were 30 years old or less, and this contrasts markedly with the published literature. Age modifies the frequency of the dermatome afflicted: more cranial and less thoracic manifestations were observed with increasing age. Almost all patients reported symptoms which may be attributed to a prodromal phase, especially pain in the affected dermatome (82%). The incidence of postherpetic neuralgia was 28%. A complicated disease course such as visceral, ocular, or otological involvement, or progression to additional dermatomes was seen in almost 10% of the patients.

Adolescent↗
PubMed1985

[Demography and reproduction of Macaca sylvanus in different habitats in Algeria].

Usually described as a cedar forest monkey, the Barbary macaque in effect has colonized a great variety of habitat types. At the moment, it is not known to what extent these different habitats are suitable for the species' survival. We tried to answer this question by comparing the demography of three monkey troops: one lives in a deciduous oak forest; the second lives in an nondeciduous cedar-green oak forest while the third is found on rocky ridges of mountains without any arborescent vegetation. In the three sites, there is a true seasonal breeding season with most births taking place in April to May and most matings occurring in November to December. Details are given on reproduction parameters (sexual activity of females; fertility rates; young survival...). Monkeys densities are higher in cedar forest than in deciduous forest. The smallest density is found on mountain ridges. Forest troops are more numerous, highly stable; their growth rate is better and the population is relatively young. The situation is slightly better still in the cedar forest than in the oak forest with a sex ratio more in favor of females and a better survival of the young. The troop of the mountain ridges is an unstable group ranging from 10 to 25 individuals; the population is aging, with a low birth rate and more male infants surviving compared with females. Demographic differences between sites are discussed according to climate, food availability and human influences (tree-clearing and overgrazing). Conclusions are drawn from this situation, for species conservation.

Algeria↗
PubMed2006

Negative relationship between dispersal distance and demography in butterfly metapopulations.

Little is known about the connection between demography and dispersal in metapopulations. The meta-analysis of the population time series of five butterfly species indicated that (meta)population dynamics are driven by density-dependent factors. Inter-specific comparison reveals a significant inverse relationship between population growth rate and the magnitude of dispersal distance. As the range of dispersal distances is constrained by the patch system, dispersing individuals moving too far away would (probably) get lost. This generates selective pressures on individuals with a high dispersal propensity, but favors individuals investing more in reproduction and results in a higher (meta)population growth rate. From a conservation perspective, individuals from (meta)populations and species sacrificing dispersal for the sake of reproductive performances are most vulnerable because of their higher sensitivity to stochastic events: the temporal variation of growth rate was much higher in the two metapopulations where dispersal was limited.

Animals↗
PubMed2001

Projection of diabetes burden through 2050: impact of changing demography and disease prevalence in the U.S.

OBJECTIVE: To project the number of people with diagnosed diabetes in the U.S. through 2050, accounting for changing demography and diabetes prevalence rates. RESEARCH DESIGN AND METHODS: We combined age-, sex-, and race-specific diagnosed diabetes prevalence rates-predicted from 1980-1998 trends in prevalence data from the National Health Interview Survey-with Bureau of Census population demographic projections. Sensitivity analyses were performed by varying both prevalence rate and population projections. RESULTS: The number of Americans with diagnosed diabetes is projected to increase 165%, from 11 million in 2000 (prevalence of 4.0%) to 29 million in 2050 (prevalence of 7.2%). The largest percent increase in diagnosed diabetes will be among those aged > or =75 years (+271% in women and +437% in men). The fastest growing ethnic group with diagnosed diabetes is expected to be black males (+363% from 2000-2050), with black females (+217%), white males (+148%), and white females (+107%) following. Of the projected 18 million increase in the number of cases of diabetes in 2050, 37% are due to changes in demographic composition, 27% are due to population growth, and 36% are due to increasing prevalence rates. CONCLUSIONS: If recent trends in diabetes prevalence rates continue linearly over the next 50 years, future changes in the size and demographic characteristics of the U.S. population will lead to dramatic increases in the number of Americans with diagnosed diabetes.

Adolescent↗