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PubMed1990

Fertility in anthropological populations.

"In this review I draw upon statistical demography and, to a lesser extent, reproductive endocrinology to formulate a coherent strategy for investigating fertility and reproduction in anthropological populations. The object, it must be emphasized, is not to reduce anthropology to demography or endocrinology, but rather to acquaint anthropologists with a powerful set of tools with which they can address issues of anthropological interest." The author first discusses the concept of natural fertility. Next, he summarizes the most significant generalizations concerning variations in fertility among preindustrial societies using the concept of proximate determinants developed by John Bongaarts. Finally, he outlines an alternative approach that might be more suited to the analysis of such fertility variations.

Anthropology↗
PubMed1991

The challenge facing population geography.

The current status of the study of population geography is examined, with some reference to the situation in the United Kingdom. The authors note that whereas the volume of studies in this area indicate its healthy growth, the subdiscipline has become increasingly distant from mainstream geography and runs the risk of being absorbed into general demography. The authors suggest that "population geographers, while taking a serious interest in the methods and philosophy of the neighbouring discipline of demography, should look elsewhere to find direction for their subdiscipline."

Demography↗
PubMed2006

Simulations provide support for the common disease-common variant hypothesis.

The success of mapping genes involved in complex diseases, using association or linkage disequilibrium methods, depends heavily on the number and frequency of susceptibility alleles of these genes. These methods will be economically and statistically feasible if common diseases are usually influenced by one or a few susceptibility alleles at each locus (common disease-common variant, CDCV, hypothesis), but not so if there is a high degree of allelic heterogeneity. Here, we use forward-time population simulations to investigate the impact of various genetic and demographic factors on the allelic spectra of human diseases, on the basis of two models proposed by Reich and Lander and by Pritchard. Factors considered are more complex demographies, a finite-allele mutation model, population structure and migration, and interaction between disease susceptibility loci. The conclusion is that the CDCV hypothesis holds and that the phenomenon is caused by transient effects of demography (population expansion). As a result, we devise a multilocus generalization of the Reich and Lander model and demonstrate how interaction between loci with respect to their response to selection may lead to complex effects. We discuss the implications for mapping of complex diseases.

Alleles↗
PubMed1999

Population, ethics, and equity.

Demography is impregnated, more or less explicitly, with ethical contents. This is apparent in the words used to support data, which change over time (e.g., the term "illegitimate child" is no longer used). Ethical principles must be analyzed because demography concerns both public policies and individual choice. There is a conflict in this area between the idea of the ethical state, dictating personal behaviors to citizens, and that of decisions based on freedom, supported by three shared values: human rights, pluralism, and equity. This paper examines how these could be reinterpreted in the context of choices regarding population.

Adult↗
PubMed2006

Demographic models inform selection of biocontrol agents for garlic mustard (Alliaria petiolata).

Nonindigenous invasive plants pose a major threat to natural communities worldwide. Biological control of weeds via selected introduction of their natural enemies can affect control over large spatial areas but also risk nontarget effects. To maximize effectiveness while minimizing risk, weed biocontrol programs should introduce the minimum number of host-specific natural enemies necessary to control an invasive nonindigenous plant. We used elasticity analysis of a matrix model to help inform biocontrol agent selection for garlic mustard (Alliaria petiolata (M. Bieb.) Cavara and Grande). The Eurasian biennial A. petiolata is considered one of the most problematic invaders of temperate forests in North America. Four weevil species in the genus Ceutorhynchus (Coleoptera: Curculionidae) are currently considered potential biocontrol agents. These species attack rosettes (C. scrobicollis), stems (C. roberti, C. alliariae), and seeds (C. constrictus) of A. petiolata. Elasticity analyses using A. petiolata demographic parameters from North America indicated that changes in the rosette-to-flowering-plant transition and changes in fecundity consistently had the greatest impact on population growth rate. These results suggest that attack by the rosette-feeder C. scrobicollis, which reduces overwintering survival, and seed or stem feeders that reduce seed output should be particularly effective. Model outcomes differed greatly as A. petiolata demographic parameters were varied within ranges observed in North America, indicating that successful control of A. petiolata populations may occur under some, but not all, conditions. Using these a priori analyses we predict: (1) rosette mortality and reduction of seed output will be the most important factors determining A. petiolata demography; (2) the root-crown feeder C. scrobicollis will have the most significant impact on A. petiolata demography; (3) releases of single control agents are unlikely to control A. petiolata across its full range of demographic variability; (4) combinations of agents that simultaneously reduce rosette survival and seed production will be required to suppress the most vigorous A. petiolata populations. These predictions can be tested using established long-term monitoring sites coupled with a designed release program. If demographic models can successfully predict biocontrol agent impact on invasive plant populations, a continued dialogue and collaboration between empirical and theoretical approaches may be the key to the development of successful biocontrol tactics for plant invaders in the future.

Animals↗
PubMed2002

A comparison of research general practices and their patients with other practices--a cross-sectional survey in Trent.

BACKGROUND: When interpreting results of studies undertaken by research networks we need to know how representative volunteer practices and their registered patients are of the total population of practices and patients in their locality. AIM: To compare the following in research and non-research general practices in one region: practice and population demography, morbidity and mortality, selected performance indicators, and health outcomes. DESIGN OF STUDY: Cross-sectional survey. SETTING: Sixty-six Trent Focus Collaborative Research Network general practices and 749 other general practices in Trent, United Kingdom. METHOD: Practice characteristics and GP contract data were obtained from the NHS Executive, Quarry House, Leeds. The Trent Regional NHS Hospital Admission Database was searched to identify all relevant admissions to hospital from all practices between 1 April 1993 and 31 March 1997. Ward-linked data on cancer were obtained from the Trent Cancer Registry. RESULTS: Of the 815 general practices in Trent Region in the study period, 66 (8%) were in the Trent Focus network. They were more likely to be involved in training GPs and to have a female partner. They tended to be larger, with fewer single-handed doctors and younger GPs. Network practices prescribed a higher proportion of generics (median % prescribed/practice = 70%, versus 51%, Mann-Whitney U = 1615, P<0.0001). There were no clinically important differences between hospital admission rates between the two groups or waiting times for surgical procedures. There was no difference in the incidence of cancer and standardised mortality ratios related to the electoral wards of the GP surgery. CONCLUSION: Although there were differences in practice structure and some aspects of performance, we found no important differences in the demography of registered patients, nor in morbidity, mortality, or access to or use of secondary care.

Cross-Sectional Studies↗
PubMed2006

Rural health's demographic destiny.

Demography is the study of the size and composition of populations. Populations change size through births, deaths and net-migration. Over time, mortality, fertility and migration patterns create populations that may be large or small, young or old, growing or declining. Rural and remote Australia has a unique demography that determines its health problems and health service needs. The tendency of young adults to leave rural and remote areas for cities means that they leave behind communities which are, on average, older than those found in the cities. Rural and remote women have slightly more children at significantly younger ages, but because of out-migration, the actual number of babies born outside of the cities is smaller than would be expected. Most rural and remote areas already have a high proportion of their population over 65 years old. Many communities with an older population are declining in absolute numbers but the need for health services may be greater than required for smaller, younger communities. In contrast to the trends in total population, the rural and remote Aboriginal and Torres Strait Islander population is growing rapidly. This is the result of a higher proportion of young people, higher fertility rates and lower rates of moving to cities. The health characteristics of rural and remote Australia increasingly reflects the higher morbidity of Indigenous and older people. Responding to this demographic destiny is the present and future challenge.

Adolescent↗
PubMed2006

The main trends in the palaeodemography of the 7th-18th century population of Latvia.

The study represents palaeodemographic research of osteological material of 3304 individuals from the funds of the Anthropological Laboratory of the Institute of History of the University of Latvia in Riga, dating from the 7th to the 18th century AD. Compensated life expectancy at birth is varying between 20.3 and 22.2 years during the research period. Crude mortality has changed between 49.3 and 45% per hundred. In the early period (7th-13th century) there is a significant male prevalence (2.2-1.4); female life expectancy at the age of 20 is on average 6.6 years less than for males. This difference decreases to 5.4 years in the 13th-18th century. According to historical demography, female life span exceeded male only in the 2nd half of 19th century. The palaeodemographic data indicate that in the 7th-18th century, women in Latvia gave birth to a mean of 4-5 children (the figure includes childless women), of whom half, at most 2-2.5, reached reproductive age, on account of high child mortality. The net reproductive rate R0 (the number of descendants per individual of the parents' generation) varies between 1 and 1.25 in the study period. Concerning the completely excavated cemeteries of Lejasbiteni (7th-10h century) and Daudziesi (16th-17th century), it was possible to calculate the size and structure of the populations that had used these cemeteries. They were similar, having 45.3-49.9% of children up to an age of 14 and 24-28% individuals over the age of 30. According to historical demography, radical improvement of the demographic situation in Latvia began in the second half of the 19th century, when the process of demographic transition in Latvia started.

Adolescent↗
PubMed1977

[Population problems of the present (author's transl)].

At present objective predications on the trend of the population development at give economic and social conditions are very difficult since neither the axiom to report the facts correctly nor the axiom of neutrality in reporting determine what should or should not be included into the description of a situation. Common expressions such as population politics, marriage fatigue, contraction of the birth rate, generative behavior, contraception, termination of pregnancies, birth corntol capitalist economic order are loaded with emotions and can therefore not be considered to be neutral determinants in the description. In the field of demography and sociology no exact methodology and theory comparable to the natural sciences is existent. The solution to the described problem is probably linked to the question whether increasing technology and increasing intricacy of the organizations and increasing productions are compatable with the improvement of individual life expression. Temporarily attention is diverted by theoretical fashion trends, however old interest in finding the truth is not eliminated and the realization that the wish for a scientific solution is not within the realm of possibility, leads to resignation. Clarification of the basic factors requires a lot of individual thought. Demography and sociology are in danger when the demographer and sociologic identify with a certain economic or sociologic system, since this threatens to eliminate logical thought. Divergent opinions are given factors in any demographic or sociologic problem and must be accepted although they should always be criticized.

Demography↗
PubMed2006

Life history in male mandrills (Mandrillus sphinx): physical development, dominance rank, and group association.

We assess life history from birth to death in male mandrills (Mandrillus sphinx) living in a semifree-ranging colony in Gabon, using data collected for 82 males that attained at least the age of puberty, including 33 that reached adulthood and 25 that died, yielding data for their entire lifespan. We describe patterns of mortality and injuries, dominance rank, group association, growth and stature, and secondary sexual character expression across the male lifespan. We examine relationships among these variables and investigate potential influences on male life history, including differences in the social environment (maternal rank and group demography) and early development, with the aim of identifying characteristics of successful males. Sons of higher-ranking females were more likely to survive to adulthood than sons of low-ranking females. Adolescent males varied consistently in the rate at which they developed, and this variation was related to a male's own dominance rank. Males with fewer peers and sons of higher-ranking and heavier mothers also matured faster. However, maternal variables were not significantly related to dominance rank during adolescence, the age at which males attained adult dominance rank, or whether a male became alpha male. Among adult males, behavior and morphological development were related to a male's own dominance rank, and sons of high-ranking females were larger than sons of low-ranking females. Alpha males were always the most social, and the most brightly colored males, but were not necessarily the largest males present. Finally, alpha male tenure was related to group demography, with larger numbers of rival adult males and maturing adolescent males reducing the time a male spent as alpha male. Tenure did not appear to be related to characteristics of the alpha male himself.

Age Factors↗
PubMed2000

On the genealogy of a sample of neutral rare alleles.

This paper concerns the genealogical structure of a sample of chromosomes sharing a neutral rare allele. We suppose that the mutation giving rise to the allele has only happened once in the history of the entire population, and that the allele is of known frequency q in the population. Within a coalescent framework C. Wiuf and P. Donnelly (1999, Theor. Popul. Biol. 56, 183-201) derived an exact analysis of the conditional genealogy but it is inconvenient for applications. Here, we develop an approximation to the exact distribution of the conditional genealogy, including an approximation to the distribution of the time at which the mutation arose. The approximations are accurate for frequencies q<5-10%. In addition, a simple and fast simulation scheme is constructed. We consider a demography parameterized by a d-dimensional vector alpha=(alpha(1), em leader, alpha(d)). It is shown that the conditional genealogy and the age of the mutation have distributions that depend on a=qalpha and q only, and that the effect of q is a linear scaling of times in the genealogy; if q is doubled, the lengths of all branches in the genealogy are doubled. The theory is exemplified in two different demographies of some interest in the study of human evolution: (1) a population of constant size and (2) a population of exponentially decreasing size (going backward in time).

Algorithms↗
PubMed2003

Antidepressant drug use in general practice: inter-practice variation and association with practice characteristics.

OBJECTIVE: The use of antidepressants (ADs) has escalated and prompted considerable debate. Many depressed patients go unrecognised or under-treated and the area of indication of the new ADs is widening. The aim of this study was to analyse (i). the variation in general practitioners' prescribing of ADs by comparing with prescribing of other drug groups and (ii). whether the general prescribing behaviour, practice activity and demography are associated with the AD prescribing. METHODS: Analysis of AD prescribing patterns among 174 general practices (93.5%) in the County of Funen, Denmark. Age- and sex-standardised 1-year incidences and prevalences of AD prescribing for patients listed were calculated using individual prescription data from Odense University Pharmacoepidemiologic Database. Data about health services and practice demography were obtained from the Health Insurance Register. The variation in AD 1-year prevalence was compared with other drug groups by a variation index (90%/10% percentile). Univariate linear regression analysis was used to examine associations between practice characteristics and prescribing. RESULTS: The 1-year prevalence of AD prescribing varied sixfold, no more than the prevalence of five other drug groups. Practices with high yearly: general prescribing prevalence, mean number of drugs per medicated patient, number of surgery consultations/100 patients and counsellings/100 surgery consultations showed the highest yearly prevalence of AD prescribing. Single-handed practices had higher AD prescribing rates than partnerships. The relative use of selective serotonin re-uptake inhibitors and other new ADs showed only little variation (10% and 90% percentiles as close as 66-86%), but practices with high 1-year prevalence and incidence most often chose the new ADs. CONCLUSION: Analysis of inter-practice variation showed no extraordinary quality problems with regard to AD prescribing, but does not exclude that there might be problems. The general prescribing pattern of the general practitioners seems essential to their attitude to AD prescribing. The relationship between counselling and prescribing was a feature specific to ADs and deserves further investigation. Quality indicators are needed to understand differences in AD prescribing, and studies based on prescription data have to be supplemented with individual clinical data.

Adult↗
PubMed2000

Hip fracture audit: time for standards to be evidence-based.

Hip fractures are a common and increasing problem. Outcome varies considerably between hospitals. The reasons for this variability are complex. To reduce inequality in patient outcome, management guidelines should be evidence-based. In order to assess quality of care, audit methods and targets should also be evidence-based. Most hip fracture audit in the UK is based upon non evidence-based guidelines and uses parameters of process rather than outcome. Current audit tools are insufficiently sensitive to account for differences in demography between hospitals. This may produce misleading results. In the space of 5 years, only modest improvements have been made in the care of patients with hip fracture. Audit tools should look at pre-existing comorbidity and functional outcome as well as the process of care, mortality and length of hospital stay. Future guidelines should be evidence-based, concentrate on outcome measures, and account for variations in demography.

Evidence-Based Medicine↗
PubMed1998

Effects of Tracking by Armored Vehicles on Townsend's Ground Squirrels in the Orchard Training Area, Idaho, USA

/ Maintaining raptor populations is a primary objective of the legislation that designates the Snake River Birds of Prey National Conservation Area. Army training activities could influence habitat quality for raptors by changing the density, productivity, or behavior of their Townsend's ground squirrel (Spermophilus townsendii) prey. These changes could occur directly or as a result of changes in the vegetation available as food and cover for the ground squirrels. We assessed the effects of long-term tracking by armored vehicles by comparing 9-ha areas in sagebrush (Artemisia tridentata) -dominated shrubsteppe and bluegrass (Poa secunda) -dominated grasslands subjected to low-intensity tracking for approximately 50 years with others that had not been tracked. We did not detect any effect on ground squirrel population dynamics associated with long-term tracking. Although densities of adults and juveniles tended to be higher in the areas exposed to such tracking, we attribute this difference to other factors that varied spatially. To determine short-term (two-year) effects, we experimentally tracked two sagebrush and two grassland sites with an M-1 tank after animals had begun their inactive season. In the following two active seasons we monitored squirrel demography and behavior and vegetative characteristics on the experimentally tracked sites and compared the results with control sites. Although we experimentally tracked approximately 33% of the surface of each of four sites where ground squirrel densities were assessed, the tracking had a detectable effect only on some herbaceous perennials and did not influence ground squirrel densities or behavior significantly during the subsequent two active seasons. We conclude that tracking after the start of the inactive season is likely to influence ground squirrel demography or behavior only if vegetation cover is substantially changed by decreasing coverage of preferred food plants or increasing the coverage of annual grasses and forbs that are succulent for only a short time each year.KEY WORDS: Armored vehicle tracking; Ground squirrels; Spermophilus townsendii; Behavior; Vegetation; Population density effects

Journal Article↗
PubMed2005

Patterns, causes and consequences of regional variation in the ecology and life history of a reef fish.

Many species vary in their ecology across their geographic ranges in response to gradients in environmental conditions. Such variation, which can influence life history traits and subsequent demography of populations, usually occurs over large spatial scales. However, describing and understanding the causes of such variation is difficult precisely because it occurs over such large spatial scales. In this study, we document spatial variation in the ecology of a common reef fish, Stegastes beebei, in the Galápagos Islands and test a number of potential causal mechanisms. The pattern resembles that seen in latitudinal variation: individuals are larger, occur in higher densities, and live longer in the coldest region of the islands than those in the warmest region. However, in this system, demography varies among regional populations separated by <150 km. Preferred nutritious algae are more available in the cold region and comprise a greater proportion of the diet of fish in this region. Per gram reproductive effort appears to be strongly related to temperature, despite differences in the gross magnitude and timing of reproduction in different regions. A model of reproductive output suggests that fish in the warmest region are allocating a greater proportion of available energy to reproduction, resulting in apparent regional life history tradeoffs. Our data suggest that regional demographic differences in S. beebei may be driven by a combination of variation in food availability and an environmentally mediated life history tradeoff.

Animals↗
PubMed2005

Demographic consequences of age-structure in extreme environments: population models for arctic and alpine ptarmigan.

Organisms living in arctic and alpine environments are increasingly impacted by human activities. To evaluate the potential impacts of global change, a better understanding of the demography of organisms in extreme environments is needed. In this study, we compare the age-specific demography of willow ptarmigan (Lagopus lagopus) breeding at arctic and subalpine sites, and white-tailed ptarmigan (L. leucurus) breeding at an alpine site. Rates of egg production improved with age at the alpine and subalpine sites, but the stochastic effects of nest and brood predation led to similar rates of annual fecundity among 1-, 2-, and 3+-year-old females. All populations had short generation times (T<2.7 years) and low net reproductive rates (R0<1.2). Stable age distributions were weighted towards 1-year-old females in willow ptarmigan (>59%), and to 3+-year-old females in white-tailed ptarmigan (>47%). High damping ratios (rho>3.2) indicated that asymptotic estimates were likely to match natural age distributions. Sensitivity and elasticity values indicated that changes in juvenile survival would have the greatest impact on the finite rate of population change (lambda) in willow ptarmigan, whereas changes to the survival of 3+-year-old females would have a greater effect in white-tailed ptarmigan. High survivorship buffers white-tailed ptarmigan in alpine environments against the potential effects of climate change on annual fecundity, but may make the species more sensitive to the effects of pollutants or harvesting on adult survival. Conversely, processes that reduce annual fecundity would have a greater impact on the population viability of willow ptarmigan in arctic and subalpine environments. If these same demographic patterns prove to be widespread among organisms in extreme environments, it may be possible to develop general recommendations for conservation of the biological resources of arctic and alpine ecosystems.

Age Distribution↗
PubMed2006

Turbidity mitigates lead toxicity to cladocerans (Cladocera).

To test the hypothesis that sediment would have a synergistic effect on the toxicity of lead to cladocerans, we performed life table demography experiments with two pelagic (Diaphanosoma birgei and Moina micrura) and one littoral (Alona rectangula) cladoceran species. Life table demography experiments were conducted at three levels of turbidity (0, 17 and 170 NTU) and six concentrations of lead (as PbCl2) from 0 to 0.71 mg l(-1). Median lethal concentrations (LC50) forA. rectangula, D. birgei and M. micrura were 7.06 +/- 0.39, 3.16 +/- 0.25 and 3.24 +/- 0.69 mg l(-1) of Pb. Life table study showed that in general, the presence of sediments in test jars allowed an overall increase of 20-75% in both survivorship and reproduction of the cladoceran species exposed to different concentrations of Pb. At 0.04 mg l(-1) of Pb, the population growth rates were 0.127 forA. rectangula, 0.037 for D. birgei and 0.471 d(-1) for M. micrura in the absence of sediments but were elevated in their presence (0.309, 0.141 and 0.722 d(-1), respectively). The data have been discussed in relation to their importance in shallow, turbid Mexican waterbodies.

Animals↗
PubMedDate not supplied

[Epidemiological characteristics of bladder tumors in the Cuenca area throughout a seventeen-year period].

OBJECTIVE: Bladder cancer is such an important health problem and accounts for most of the surgical duty in the urology departments. We achieve to draw the features of patients diagnosed with bladder tumors in the Cuenca area throughout a seventeen-year period. MATERIAL AND METHOD: From January 1985 to December 2002 we recorded in the Cuenca area the entire urologic tumor recently diagnosed. The following features were recorded: gender, age, pathology, TNM classification, risk factors (alcohol, cigarette smoking and coffee), social demography (rural/ urban) and the presence of metastasis. RESULTS: We achieve significant differences within pathology, age at diagnosis, incidence, social demography and some risk factors throughout the seventeen-year period. CONCLUSIONS: More bladder cancers are diagnosed along this time, more of them are infiltrating, in an aging population and from a rural precedence although a slightly decrease in the overall population in this are has been documented.

Adult↗