Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Population Projection”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMed2002

Functionality of divergence and convergence in a model of the insect olfactory system.

Recent studies have shown that the insect olfactory system uses a spatio-temporal encoding of odours in the population of projection neurons in the antennal lobe, and suggest that the information thus coded is spread across a large population of Kenyon cells in the mushroom bodies. At this stage, the temporal part of the code might be transformed into a spatial code, especially via the temporally sensitive mechanisms of paired-pulse facilitation and feedback inhibition with its possible associated rebound. We explore here a simple model of the olfactory system using a three-layer network of formal neurons, comprising a fixed number (three) of projection and inhibitory neurons, but a variable number of Kenyon cells. We show how enlarging the divergence of the network (i.e. the ratio between the number of Kenyon cells to the number of input - projection - neurons) alters the number of different output spatial states in response to a fixed set of spatio-temporal inputs, and may therefore improve its effectiveness in discriminating between these inputs. Such enlarged divergence also reduces the variation of this effectiveness among random realizations of the network connectivity. Our model shows that the discriminative effectiveness first increases with the divergence, and then plateaus for a divergence factor of approximately 20. The maximal average number of different outputs was 470.2, which was computed from some simulations with random realizations of connectivity and with a set of 512 possible inputs. The discriminative effectiveness of the network is sensitive to paired-pulse facilitation, and especially to inhibition with rebound.

Animals↗
PubMedDate not supplied

Projecting utilization of hospital in-patient days in The Netherlands: a time-series analysis.

The object was to model and project utilization of hospital in-patient days for selected diseases in The Netherlands. We used sex- and age-specific standardized monthly utilization of hospital in-patient days during 1980-90 for lung cancer, diabetes, coronary heart disease, stroke, and pneumonia. These data were supplied by the Health Care Information Centre (Stichting Informatiecentrum voor de Gezondheidszorg). We applied Box-Jenkins time-series analysis seasonal autoregressive integrated moving-average (SARIMA) models. Estimated models are tested by considering the Portmanteau test and the Akaike information criterion. SARIMA models give an adequate representation of hospital-in-patient-days utilization for the major sex and age classes of most selected diseases. Poor modelling results are obtained for diabetes in all sex and age groups and in elderly women with coronary heart disease or with stroke. Seasonality is an important factor in most of the models that we have estimated, particularly for utilization of pneumonia and stroke patients. The major trends in standardized in-patient days are downward, and projected 1995 levels of standardized utilization are below the 1990 levels for all the selected diseases. Population-based projections for 1995 are lower than the 1990 projections only for lung cancer and diabetes. The adequacy of the SARIMA models appears to be sensitive with respect to the parameter in the Portmanteau test. We discuss two possible explanatory developments for in-patient-days utilization: (i) developments in the provision of hospital care, and (ii) epidemiological developments. The selected diseases showed a decreasing mean duration of stay in 1980-90. Only for coronary heart disease did a rise in discharges in the same period outweigh this trend. We assessed contrasts between published epidemiological developments and the trends in in-patient-days utilization. Possible explanations concern shifts from in-patient to out-patient care and changes in treatment. Finally, complementary to our SARIMA models, the investigation of future in-patient days utilization by means of scenario analytic approaches remains important.

Adolescent↗
PubMed1986

Projection of death rates from ischemic heart disease in Japan, 1985-2000.

Death rates from all forms of ischemic heart disease and acute myocardial infarction were projected between 1985 and 2000 A.D., based on vital statistics from 1973 to 1982 and the estimated population by sex and age groups in Japan. It is predicted that the crude death rate from ischemic heart disease will increase (+1.4% per year for males and +1.8% for females), and that the age-adjusted death rate will decrease (-1.1% per year for males and -1.4% for females). The crude death rate from acute myocardial infarction is predicted to increase steadily (+2.4% per year for males and +2.2% for females), though the age-adjusted rate will decline slightly (-0.5% per year for males and -1.0% for females) throughout this period. The crude death rate from acute myocardial infarction is predicted to increase more than the rate from ischemic heart disease. It is estimated that the total number of deaths will increase from 48,000 (males and females combined) in 1982 to 72,000 in 2000 for ischemic heart disease, and from 29,600 in 1982 to 45,500 in 2000 for acute myocardial infarction.

Adult↗
PubMed1989

Structural and functional properties of reticulospinal neurons in the early-swimming stage Xenopus embryo.

This study presents direct evidence that in Xenopus laevis embryos ipsi- and contralaterally descending reticulospinal fibers from the caudal brain stem project to the spinal cord, where they directly contact primary motoneurons. At stage 30, occasional contacts between primary motoneurons and descending axons are present. These contacts are possibly already functional since presynaptic vesicles were sometimes observed. Furthermore, the physiological data obtained in this study suggest that reticulospinal neurons in the caudal brain stem are involved in the central generation of early swimming. The first ingrowth of reticulospinal axons was observed in the rostral spinal cord after application of HRP to the caudal brain stem of stage 27/28 embryos. By stage 32, many supraspinal axons could be found in the spinal cord at the level of the 12/13th myotome, near the time of the first rhythmic swimming. Both lamellipodial and varicose growth cones were found. Intracellular recordings from the brain stem and extracellular recordings from the myotomal muscles in curarized embryos around stage 30 revealed neurons in the caudal brain stem which were active during early fictive swimming. After intracellular staining with Lucifer yellow neurons with descending axons were found in the brain-stem reticular formation. These reticulospinal neurons showed "motoneuron-like" phasic activity, producing one spike each swimming cycle. Rhythmically occurring spikes with swimming periodicity were superimposed on a sustained depolarization level of some 5-30 mV. Reticulospinal neurons in the brain stem resemble descending interneurons in the spinal cord by their morphology, projection pattern, and activity during early swimming. Reticulospinal neurons and descending interneurons might therefore form one continuous population of projecting interneurons with a different location but a similar function. In support of this we propose that the embryonic brain-stem reticular formation forms part of the swimming pattern generator.

Animals↗
PubMed2005

Laser scanning tomography of the optic nerve head in a normal elderly population: the Bridlington eye assessment project.

PURPOSE: To assess optic nerve head topographic parameters using the Heidelberg Retina Tomograph (HRT) II (Heidelberg Engineering GmbH, Dossenheim, Germany) in a normal elderly population. METHODS: Optic nerve head analysis of 918 eyes of 459 normal elderly patients was performed. All patients were consecutive in a cohort screened for eye disease. Normal subjects were defined with a normal visual field on automated suprathreshold screening, intraocular pressure less than 22 mmHg, and minimum corrected visual acuity of 6/12. All optic discs were contoured by two investigators and the mean parameters analyzed. The effects of age, sex, and disc size were assessed. RESULTS: Subjects' (262 women and 197 men) mean age was 72.6 +/- 5.1 (SD) years (range, 65.5-89.3). Mean +/- SD global disc area, cup/disc area ratio, and neuroretinal rim area were 1.98 +/- 0.36 mm2, 0.22 +/- 0.14, and 1.52 +/- 0.31 mm2, respectively. Disc area did not differ significantly based on eye side or sex. The women were found to have a significantly larger rim volume, mean retinal nerve fiber layer (RNFL) thickness, and cross-sectional area than the men and tended to have smaller cup areas/volumes and cup/disc area ratios. Most tomography parameters were found to be significantly influenced by disc size. CONCLUSIONS: To the authors' knowledge, this is the first large study of optic nerve head parameters in the elderly normal population using the HRT II. This age range is particularly relevant to glaucoma detection and pertinent to discriminant analyses separating normal subjects from glaucoma in screening for the disease. Given the systematic differences between the parameters in men and women, reference ranges should be quoted by sex.

Aged↗
PubMed1999

Self-reported assessment of visual function in a population-based study: the SEE project. Salisbury Eye Evaluation.

PURPOSE: To report on the usefulness of the Activities of Daily Vision Scale (ADVS) questionnaire for assessing visual functioning, a population-based sample of elderly Americans. METHODS: The ADVS questionnaire was administered to a population-based sample of 2520 community-dwelling individuals 65 to 84 years of age in Salisbury, MD. Items and subscales were evaluated for internal consistency, item discrimination, and content validity. Published subscale groupings and item associations in our population were compared for coherence using correlation, factor, and cluster analyses. Whole-sample and race- and gender-specific analyses were conducted. External validity was explored by regressing ADVS scores on standard psychophysical vision measures. RESULTS: ADVS scores were skewed to high visual functioning levels; approximately 60% of the population had function scores of 95 or better (of a possible 100). The overall, night driving, and near vision scales were internally consistent and had strong item-subscale associations; the day driving and glare subscales were not acceptable regarding these properties. The far vision subscale was acceptably scalable but only weakly differentiated from the other subscales. Overall, night driving, near vision, and far vision scores were all statistically and independently associated with multiple psychophysical vision measures. Findings were consistent across race and gender subgroups. CONCLUSIONS: As assessed by the ADVS, reported visual functioning is high in our representative older population. The overall scale and selected subscales effectively distinguish persons along a spectrum of ability. They correlate with measures of visual impairment in a reasonable way and thus hold promise for risk factor investigations. The published day driving and glare subscales should be examined for relevance and consistency before being applied in population-based settings. Methods specific to population-based settings should be investigated for their ability to better elicit additional visual function dimensions and early visual disability.

Activities of Daily Living↗
PubMed2002

Population screening for hemochromatosis--are we finding people with a disease or a biochemical curiosity?

Hemochromatosis is a common genetic disease in which early diagnosis and treatment results in an excellent long-term prognosis. Population screening projects have been completed that included iron tests and genetic testing. In this review, the controversial issues surrounding population screening for hemochromatosis are explored in the context of available information from large screening studies.

Genetic Counseling↗
PubMedDate not supplied

The formal demography of families and households: an overview.

"The objective of the present paper is to give a brief overview of the subject matter of the formal demography of the family. Selected references are included, but no attempt is made to be exhaustive. No discussion of socio-economic determinants or consequences is included, because this overview is limited to the formal aspects of the field. "The...paper is divided into five parts. The first deals with the descriptive analysis of family and household size and composition, from both a cross-sectional and a longitudinal perspective. The next two sections discuss, in order, demographic determinants and consequences. This is followed by a brief section on projection methods and the conclusion."

Demography↗
PubMed2004

Causes and prevalence of visual impairment among adults in the United States.

OBJECTIVES: To estimate the cause-specific prevalence and distribution of blindness and low vision in the United States by age, race/ethnicity, and gender, and to estimate the change in these prevalence figures over the next 20 years. METHODS: Summary prevalence estimates of blindness (both according to the US definition of < or =6/60 [< or =20/200] best-corrected visual acuity in the better-seeing eye and the World Health Organization standard of < 6/120 [< 20/400]) and low vision (< 6/12 [< 20/40] best-corrected vision in the better-seeing eye) were prepared separately for black, Hispanic, and white persons in 5-year age intervals starting at 40 years. The estimated prevalences were based on recent population-based studies in the United States, Australia, and Europe. These estimates were applied to 2000 US Census data, and to projected US population figures for 2020, to estimate the number of Americans with visual impairment. Cause-specific prevalences of blindness and low vision were also estimated for the different racial/ethnic groups. RESULTS: Based on demographics from the 2000 US Census, an estimated 937 000 (0.78%) Americans older than 40 years were blind (US definition). An additional 2.4 million Americans (1.98%) had low vision. The leading cause of blindness among white persons was age-related macular degeneration (54.4% of the cases), while among black persons, cataract and glaucoma accounted for more than 60% of blindness. Cataract was the leading cause of low vision, responsible for approximately 50% of bilateral vision worse than 6/12 (20/40) among white, black, and Hispanic persons. The number of blind persons in the US is projected to increase by 70% to 1.6 million by 2020, with a similar rise projected for low vision. CONCLUSIONS: Blindness or low vision affects approximately 1 in 28 Americans older than 40 years. The specific causes of visual impairment, and especially blindness, vary greatly by race/ethnicity. The prevalence of visual disabilities will increase markedly during the next 20 years, owing largely to the aging of the US population.

Adult↗
PubMed1989

The distribution of hippocampal and spinal projecting cells in the locus coeruleus of tottering mice.

Wheat germ agglutinin conjugated to horseradish peroxidase and Fast Blue were used as retrograde tracers to examine the distribution of coeruleohippocampal and coeruleospinal somata within the locus coeruleus of normal and tottering mutant mice. The distributions of these projection neuron populations in normal mice are similar to what has been found in other species, and the distributions of these projection neurons in tottering mice are indistinguishable from those in normal mice, in spite of the norepinephrine hyperinnervation of certain locus coeruleus targets, including the hippocampus, in the tottering mutant. These observations lend support to the notion that the defect in tottering acts fairly directly on mechanisms involved in the development of locus coeruleus axonal arbors within certain target regions.

Animals↗
PubMed2003

Balancing population size and genetic information in parentage analysis studies.

In parentage analysis studies, the parameters of interest typically are not the parent assignments themselves, but population parameters such as variance in fertility, self-pollination rate, or average dispersal distances. The precision of parameter estimates is affected by two factors: the number of offspring under consideration, and the precision with which the offspring can be assigned to parents. When assignment of parents is based on genetic information, the confidence in assignments is affected by the number and polymorphism of the loci considered, and by the number of potential parents in the population. Studying larger populations may yield higher numbers of offspring, but since larger populations contain more potential parents, more (or more highly polymorphic) loci are necessary to attain a given level of confidence in the parent assignments. This article addresses how to relate the size of the population and the number of loci when designing a study. It is shown that the number of loci needed to assign all offspring unambiguously is proportional to the logarithm of the population size. In some cases, the constant of proportionality can be determined, eliminating the need for simulation-based projections. Population-wide measures of uncertainty in parent assignments are also introduced, and it is shown that holding uncertainty "steady" as the population size increases also requires increasing the number of loci proportional to the logarithm of the population size. Data from a study of self-pollination are used to illustrate the techniques suggested.

Biometry↗