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PubMed2004

Demography of human supercentenarians.

An international committee of demographers has created a carefully documented list of worldwide living supercentenarians (> or =110 years old) that has been published by the Los Angeles Gerontology Research Group on its web site and updated on a weekly basis for the past 6 years [see "snapshot" for the year 2003 in the Appendix]. What can be learned by studying this distinguished group of individuals? Also, what are the implications for understanding the fundamental biological limits to human longevity and maximum life span? Our conclusion: Although everyone agrees that average life expectancy has systematically advanced linearly over the last century, it is not realistic to expect that this pace can continue indefinitely. Our data suggest that, without the invention of some new unknown form of medical breakthrough, the Guinness Book of World Records benchmark established by French woman Jeanne Calment of 122 years, set back in 1997, will be exceedingly difficult to break in our lifetime.

Aged↗
PubMed1996

Mutual attraction: demography and life-course analysis.

Bringing together a life course and demographic perspective provides a useful framework for studying aging. This perspective conceptualizes aging as the dynamic process of cohorts moving through the life course in historical time. Each cohort is embedded in a social structure that regulates how it ages, and the social structure changes as the cohort advances through the life course over time. This view of aging provides a strategy for developing research on such basic questions as: Why is the life course structured the way it is? How, and why, does the experience of aging differ between cohorts? And how, and why, is aging experienced differentially by various segments of a cohort?

Aging↗
PubMed1989

Ethnic determinants of perinatal statistics of Chinese: demography of China, Hong Kong and Singapore.

Despite limited health resources, the Chinese have achieved reasonably good perinatal and neonatal mortality rates comparable to those of many developed countries. China, Hong Kong and Singapore, areas with different socioeconomic structures, have shared the same favourable ethnic determinants of perinatal mortality. The Chinese have much lower incidence of very low birthweight babies (less than 1000 g) and lethal congenital anomalies. The former is probably related to the rarity of teenage pregnancy, maternal smoking and alcohol consumption. Asphyxia remains a major contributor to perinatal deaths. The perinatal mortality rate in mainland China has remained relatively unchanged in contrast to the dramatic falling trend in Hong Kong and Singapore in the past two decades. This may be accounted for by differences in socioeconomic conditions despite their identical ethnic origin. Studying the Chinese sociocultural pattern may have a great impact on perinatal mortality by preventing low birthweight babies.

Age Factors↗
PubMed1993

Randomized evaluation of pulse oximetry in 20,802 patients: I. Design, demography, pulse oximetry failure rate, and overall complication rate.

BACKGROUND: Although pulse oximetry is currently in widespread use, there are few data documenting improvement in patient outcome as a result of the use of oximetry. The authors describe the study design, patient demographic findings, data validation, pulse oximetry failure rate, and overall postoperative complication rates in the first large prospective randomized multicenter clinical trial on perioperative pulse oximetry monitoring. METHODS: In five Danish hospitals, by random assignment, monitoring did or did not include pulse oximetry for patients 18 yr of age and older, whether scheduled for elective or emergency operations, or for regional or general anesthesia, except during cardiac and neurosurgical procedures. Operational definitions were established for perioperative events and postoperative complications. The data were collected preoperatively, during anesthesia, in the postanesthesia care unit, and until the day of discharge from the hospital or the seventh postoperative day. RESULTS: Of 20,802 patients, 10,312 were assigned to the oximetry group and 10,490, to the control group. In general, the demographic data, patient factors, and anesthetic agents used were distributed evenly. A slight intergroup difference was found in the distribution of age, duration of surgery, some types of surgery, and some types of anesthesia. The total failure rate of the oximetry was 2.5%, but it increased to 7.2% in patients with American Society of Anesthesiologists physical status 4 (P < 0.00001). In 14.9% of the patients, one or more events occurred in the operating room and 13.5% in the postanesthesia care unit. The overall postoperative complication rate was 9.7%. The total rates of cardiovascular and respiratory complications were 2.78% and 3.50%, respectively. Within the first seven postoperative days, 0.47% of the patients died. Anesthesia was not thought to have been solely responsible for any death, but in 7 patients (1 per 3,365), it was a possible contributory factor. CONCLUSIONS: Despite the finding of a few significant inter-group differences, the randomization was well balanced with a high validity of data. The overall postoperative complication rate was similar to that in other recent morbidity and mortality studies.

Adult↗
PubMed1989

Demography of penetrating cardiac trauma.

All cases of penetrating cardiac trauma in 1985 and 1986 in Jefferson County, Alabama, where patients dying of penetrating trauma received autopsies, were retrospectively reviewed. All hospitals in the county plus the single coroner's office provided the records of the 72 patients comprising this study. Incidents occurred most often in the home or residence (70%) by a known assailant (83%) due to domestic/social disputes (73%). Frequency was greatest in the evening hours (73% between 6:00 PM and 3:00 AM), on weekends in spring and summer. Victims tended to be male (86%), black (72%), married (46%), blue collar workers (62%). There were 41 (57%) gunshot wounds, 3 (4%) shotgun wounds, and 28 (39%) stab wounds with an associated mortality rate of 97%, 100%, and 68%, respectively. Prehospital mortality rate (dead at the scene) was 54.2% (39/72), and death on arrival was 26.4% (19/72), for a combined pretreatment mortality rate of 80.6%. All patients who arrived with no vital signs died. Mortality appeared to be related to mechanism of injury, age, race, sex, vital signs on arrival, number and specific cardiac chambers injured, associated major vascular injury, hematocrit, and mode of transportation. Mortality was not related to caliber of weapon, ethanol level, transport time, time from arrival to operation, or transfusion requirements. There were only ten survivors (1 gunshot wound and 9 stab wounds), all of whom had ventricular injuries and no associated major vascular injuries. The ten survivors represented a 71.4% (10/14) salvage rate for those victims arriving with vital signs. Complications occurred in three patients. Hospitalization averaged 7.3 days in the survivors. Penetrating cardiac trauma remains a serious, socially linked disease with a high rate of mortality. Rapid transport, aggressive resuscitation and cardiorrhaphy remain the best treatment.

Adolescent↗
PubMed1994

The effects of habitat fragmentation on demography and on the loss of genetic variation in the red squirrel.

A major problem in conservation biology is the extent to which the loss of genetic variability in isolated populations reduces their chance of survival. We present data in which the loss of genetic diversity in small and isolated populations can be directly related to population dynamics. Genetic similarity in red squirrels is inversely correlated with population size. The loss of genetic variation and the lower population densities in isolated populations are both the result of reduced immigration. Our data suggest that population processes rather than genetic problems are the real threat to small squirrel populations.

Animals↗
PubMed2004

Evolutionary history of the northern leopard frog: reconstruction of phylogeny, phylogeography, and historical changes in population demography from mitochondrial DNA.

This study uses a combined methodological approach including phylogenetic, phylogeographic, and demographic analyses to understand the evolutionary history of the northern leopard frog, Rana pipiens. We tested hypotheses concerning how (or if) known geological events and key features of the species biology influenced the contemporary geographic and genetic distribution of R. pipiens. We assayed mitochondrial DNA variation from 389 individuals within 35 populations located throughout the species range. Our a priori expectations for patterns and processes influencing the current genetic structure of R. pipiens were supported by the data. However, our analyses revealed specific aspects of R. pipiens evolutionary history that were unexpected. The phylogenetic analysis indicated that R. pipiens is split into populations containing discrete eastern or western haplotypes, with the Mississippi River and Great Lakes region dividing the geographic ranges. Nested clade analysis indicated that the biological process most often invoked to explain the pattern of haplotype position is restricted gene flow with isolation by distance. Demographic analyses showed evidence of both historical bottlenecks and population expansions. Surprisingly, the genetic evidence indicated that the western haplotypes had significantly reduced levels of genetic diversity relative to the eastern haplotypes and that major range expansions occurred in both regions well before the most recent glacial retreat. This study provides a detailed history of how a widespread terrestrial vertebrate responded to episodic Pleistocene glacial events in North America. Moreover, this study illustrates how complementary methods of data analysis can be used to disentangle recent and ancient effects on the genetic structure of a species.

Animals↗
PubMed1994

Overview: demography, epidemiology and psychopharmacology--making sense of the connections.

This overview discusses the five papers covering demographic and prevalence issues in terms of the commonalities and differences across psychoactive substances, particularly as they pertain to the relationship between demographic factors and the prevalence of substance abuse. This overview also concerns itself with gaps in knowledge, methodological issues and future directions for research. It begins with some basic definitions and fundamental questions. A brief review of the salient points of each paper is then provided, followed by a more synthetic discussion of methodological and theoretical issues. It closes with some speculative ideas about the meaning of demographic variables for an understanding of substance abuse.

Alcoholism↗
PubMed2006

Mapping the social demography and location of HIV services across Toronto neighbourhoods.

In this paper we map the location and distribution of HIV service providers across Toronto neighbourhoods. Our analysis identified an uneven distribution of services across Toronto and a number of communities that are less accessible to HIV-related services. We subsequently identified three neighbourhood-level characteristics of the populations living within these communities (i.e. concentrated economic disadvantage, concentrated immigration, and residential instability). Our findings suggest a significant overlap in the location of HIV service providers and the clustering of neighbourhood-level demographic and socioeconomic factors. Some inaccessible neighbourhoods overlap with clusters of neighbourhoods with higher levels of concentrated disadvantage, immigration and percentage of black Canadians. Accessible neighbourhoods are located within the downtown core of Toronto and overlap with clusters of highly dense, younger neighbourhoods (with a high proportion of 15- to 34-year-olds who are unmarried). Our findings point to the need for policy-makers to integrate spatial analytic techniques into their examination of the types of neighbourhoods, and subsequently the community members that live within those neighbourhoods, that are potentially underserved with respect to health and social services.

Canada↗
PubMed2006

Multiscale patterns of movement in fragmented landscapes and consequences on demography of the snail kite in Florida.

1. Habitat loss and fragmentation are major factors affecting vertebrate populations. A major effect of these habitat alterations is that they reduce movement of organisms. Despite the accepted importance of movement in driving the dynamics of many natural populations, movement of vertebrates in fragmented landscapes have seldom been estimated with robust statistical methods. 2. We estimated movement probabilities of snail kites Rosthramus sociabilis within the remaining wetlands in Florida. Using both radio-telemetry and banding information, we used a multistate modelling approach to estimate transition probabilities at two temporal scales (month; year) and multiple spatial scales. We examined kite movement among wetlands altered by three different levels of fragmentation: among wetlands separated by small physical barriers (e.g. road); among wetlands separated by moderate amount of matrix (< 5 km); and among wetlands separated by extensive matrix areas (> 15 km). 3. Kites moved extensively among contiguous wetlands (movement probability 0.29 per month), but significantly less among isolated wetlands (movement probability 0.10 per month). 4. Kites showed high levels of annual site fidelity to most isolated wetlands (probability ranged from 0.72 to 0.95 per year). 5. We tested the effects of patch size and interpatch distance on movement. Our modelling indicated an effect of both distance and patch size on juveniles' movement (but not adult) when examining movements among fragments. 6. Only a small proportion of kites escaped a regional drought by moving to refugia (wetlands less affected by drought). Many individuals died after the drought. During drought adult survival dropped by 16% while juvenile survival dropped by 86% (possibly because juveniles were less likely to reach refugia). 7. We hypothesize that fragmentation may decrease kite's resistance to drought by restricting exploratory behaviour.

Animals↗
PubMed2005

Historical colonization and demography of the Mediterranean damselfish, Chromis chromis.

The desiccation of the Mediterranean Sea during the Messinian Salinity Crisis 6.0-5.3 million years ago (Ma), caused a major extinction of the marine ichthyofauna of the Mediterranean. This was followed by an abrupt replenishment of the Mediterranean from the Atlantic after the opening of the Strait of Gibraltar. In this study, we combined demographic and phylogeographic approaches using mitochondrial and nuclear DNA markers to test the alternative hypotheses of where (Atlantic or Mediterranean) and when (before or after the Messinian Salinity Crisis) speciation occurred in the Mediterranean damselfish, Chromis chromis. The closely related geminate transisthmian pair Chromis multilineata and Chromis atrilobata was used as a way of obtaining an internally calibrated molecular clock. We estimated C. chromis speciation timing both by determining the time of divergence between C. chromis and its Atlantic sister species Chromis limbata (0.93-3.26 Ma depending on the molecular marker used, e.g. 1.23-1.39 Ma for the control region), and by determining the time of coalescence for C. chromis based on mitochondrial control region sequences (0.14-0.21 Ma). The time of speciation of C. chromis was always posterior to the replenishment of the Mediterranean basin, after the Messinian Salinity Crisis. Within the Mediterranean, C. chromis population structure and demographic characteristics revealed a genetic break at the Peloponnese, Greece, with directional and eastbound gene flow between western and eastern groups. The eastern group was found to be more recent and with a faster growing population (coalescent time = 0.09-0.13 Ma, growth = 485.3) than the western group (coalescent time = 0.13-0.20 Ma, growth = 325.6). Our data thus suggested a western origin of C. chromis, most likely within the Mediterranean. Low sea water levels during the glacial periods, the hydrographic regime of the Mediterranean and dispersal restriction during the short pelagic larval phase of C. chromis (18-19 days) have probably played an important role in C. chromis historical colonization.

Animals↗