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1.
On prevalence, incidence, and duration in general stable populations.   总被引:7,自引:0,他引:7  
J M Alho 《Biometrics》1992,48(2):587-592
The relationship between prevalence, incidence, and duration of disease is studied in exponentially growing/declining stable populations. Prevalence odds is shown to be a weighted average of age-specific products between incidence and discounted disease duration. If and only if the covariance between incidence and duration is zero, does prevalence odds equal the product of average incidence and average duration. The product of averages is shown typically to overestimate prevalence in epidemiologic applications. Ignoring population growth also tends to lead to overestimation of prevalence.  相似文献   

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The associations of breastfeeding duration and milk fat composition with the developmental outcome at 1 year of age were measured within 44 infants exclusively breastfed for 3 months, out of 95 recruited at birth. Pooled breast milk (hindmilk) of the mothers was analysed at colostrum, 1, 3, 6, 9, and 12 months for total fat and fatty acid content. Infants were examined at 12 months by means of the Bayley test. There was a progressive reduction of the number of breastfed babies after the introduction of solids to 29 (6 months), 17 (9 months) and 10 (12 months). After adjusting for major confounders, infants breastfed for 6 months or longer showed a trend to have an advantage at the Bayley psychomotor developmental index compared to those breastfed >3 and <6 months (95% CI for difference: - 0.6, 13.8; P= 0.07) while the Bayley mental developmental index (MDI) was just 2.1 points higher. Among the milk fat components considered for each time-point, the total fat content at 6 months showed the strongest association with the MDI at 12 months (r=0.59, P=0.001). Prolonging breastfeeding during the weaning process may result in a better developmental performance at 12 months, possibly due to the supply of fats affecting brain composition.  相似文献   

4.
Gynecomastia has been treated surgically in 159 patients during the past 22 1/2 years. Prior to 1980, all patients had traditional excision, which was followed by a high incidence of complications and undesired sequelae, not the least of which was that the results of this aesthetic operation were often unaesthetic. Since 1980, when suction lipectomy became the cornerstone of treatment, the results have been much better. As a result, current recommendations for treatment are as follows: If the gynecomastia is entirely due to fat, suction lipectomy alone is sufficient treatment. However, since suction will not remove breast parenchyma, those patients whose gynecomastia is due to parenchymal hypertrophy also require local excision of the parenchyma. Skin excision is rarely, if ever, necessary.  相似文献   

5.
A 6-year (2004-2010) retrospective study was carried out to determine the prevalence of hydatidosis in livestock slaughtered in Mashhad abattoir, Mashhad, in north-eastern Iran and the capital of Khorasan province. Between 20 March 2004 and 19 March 2010, 5,131,485 animals (411,163 cattle; 4,547,618 sheep; 172,704 goats) were slaughtered in the study area and 388,399 (7.5%) livers and 1,139,529 (22.2%) lungs were discarded. Hydatidosis was responsible for 4% and 6.5% of total livers and lungs inspected, respectively. Of the cattle livers and lungs inspected over the survey period, 5.5% and 7.9% were condemned, respectively, because they held hydatid cysts. The corresponding values for livers and lungs of sheep (2%, 4%) and of goats (4.5%, 7.8%), respectively, were also condemned due to hydatidosis. Data showed a prominent seasonal pattern for hydatidosis. Liver condemnations due to hydatidosis were higher in winter and autumn for cattle and sheep, respectively, whereas lung condemnations were higher in summer for sheep and cattle. In goats, liver and lung condemnations were higher in winter. This could be attributed to various factors, such as sources of slaughtered animals, changes in management practice and ecological factors. The present survey provides baseline data for the future monitoring of this potentially important parasitic disease in the region.  相似文献   

6.
Cystic echinococcosis caused by Echinococcus granulosus is considered to be an important parasitic infection in livestock. In the present study, which aimed to determine the epidemiology of hydatidosis in buffalo in Iran, slaughterhouses of West Azerbaijan (Urmia), East Azerbaijan (Tabriz), Ardabil (Ardabil), Gilan (Rasht and Hashtpar) and Khuzestan (Ahvaz) were inspected. Age, sex and infected organs were recorded separately, and the observed cysts were examined for fertility and viability. Our results showed that 344 (9%) of 3832 inspected buffaloes were infected with hydatid cysts. The maximum and minimum infection rates occurred in Khuzestan (9.9%) and Ardabil (8%) provinces, respectively. There was no significant difference in the rate of infection in all provinces. Of 344 infected buffaloes, the rate of fertility was 7.3% and the rate of viability in fertile cysts was 78.75%. Hydatid cysts were more prevalent in female compared with male buffaloes (P < 0.05). There was a positive correlation between the age and number of infected hosts in all provinces except East Azerbaijan. The prevalence of infection in lungs was significantly higher than that in the livers of buffaloes in the provinces studied (P < 0.001). In conclusion, the fertility of hydatid cysts in buffaloes was low, as previously demonstrated in cattle, and this animal may play a minor role in the epidemiology of hydatidosis in Iran.  相似文献   

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Point or instantaneous sampling refers to the scoring of presence or absence of behavior at the end of equally spaced intervals of time and is used to estimate prevalence. The literature cited demonstrates that point sampling does not adequately estimate frequency or mean bout duration. A parametric model is developed based on exponentially distributed times of behavior and intervening nonbehavior, thus enabling estimators of mean bout length and incidence. Variance estimators are provided and a method is suggested for designing sample situations which control the variance of the prevalence estimator. The paper concludes the theoretical investigation with a thorough Monte Carlo investigation and application to a “real-life” problem. The point sample estimators compare favorably with continuous observation under appropriate choice of sampling interval and under approximately exponential assumptions.  相似文献   

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A survey was undertaken to evaluate how animal pain, suffering and distress are recognized and assessed in UK scientific procedure establishments designated under the Animals (Scientific Procedures) Act 1986. A total of 28 institutions were visited between June 1999 and April 2001, within which 137 people were interviewed including scientists, veterinarians and animal technicians. All 28 establishments use clinical observation sheets to assist the recognition of adverse effects, nine use score sheets and seven use computerized data management systems. Clinical signs used as indicators of potential pain, suffering or distress are largely subjective. The survey also addressed protocols and methods for avoiding and alleviating adverse effects, record keeping, review of policies and protocols and issues relating to team work and training. Respondents use a range of techniques for reducing suffering including analgesia, humane endpoints, ensuring competence and refining husbandry. All establishments review projects regularly but few have the time or resources formally to review adverse effects noted in practice and to compare observations with predictions made in licence applications. Training is very consistent between different establishments and most aim to achieve a 'team approach' for monitoring and assessing animals. Results are summarized in the present, abridged paper and set out in full in a report that can be downloaded at http://www.lal.org.uk/pain/(Hawkins 2002). The present paper and the full report, including its recommendations, are intended to provide a source of information, discussion topics and ideas for all establishments that need to monitor animal well-being.  相似文献   

11.
In a cross-sectional study, a total of 5381 slaughtered animals, namely 928 cattle, 243 buffaloes, 3765 sheep and 445 goats were inspected macroscopically for hydatid cysts in northwest Iran, with prevalence values of 38.3%, 11.9%, 74.4% and 20%, respectively, being recorded. Prevalences were higher in females compared with males, but a significant difference (P < 0.001) was only found in sheep and cattle. Most cases which were condemned were seen in the lungs of sheep (13.4%) indicating that sheep are the most important intermediate hosts for Echinococcus granulosus in this area.  相似文献   

12.
This review aims to describe changes in breastfeeding and summarise the breastfeeding rates, duration and reasons of discontinuing 'any breastfeeding' or 'exclusive breastfeeding' in P.R. China. Breastfeeding rates in China fell during the 1970s when the use of breast milk substitutes became widespread, and reached the lowest point in the 1980s. As a result many efforts were introduced to promote breastfeeding. The breastfeeding rate in China started to increase in the 1990s, and since the mid-1990s 'any breastfeeding' rates in the majority of cities and provinces, including minority areas, have been above 80% at four months. But most cities and provinces did not reach the national target of 'exclusive breastfeeding' of 80%. The 'exclusive breastfeeding' rates in minority areas were relatively lower than comparable inland provinces. The mean duration of 'any breastfeeding' in the majority of cities or provinces was between seven and nine months. The common reasons for ceasing breastfeeding, or introducing water or other infant food before four months, were perceived breast milk insufficiency, mother going to work, maternal and child illness and breast problems. Incorrect traditional perceptions have a strong adverse influence on 'exclusive breastfeeding' in less developed areas or rural areas. China is a huge country, geographically and in population size, and there is considerable ethnic diversity. Therefore breastfeeding rates in different parts of China can vary considerably.  相似文献   

13.
The use of patient contact-shielding has become a topic of intensive scientific debate. While it has been common practice during the last decades, some studies have questioned the efficiency of using such shielding while others have highlighted the inconsistencies in its application. The objective of this work is to review current recommendations and legislative documents on the use of out-of-field shielding in X-ray imaging, including those from national authorities and from international and national organisations and professional bodies.The review, performed within the framework of the activities of EURADOS Working Group 12, covers available recommendations on use of contact shielding in adult, pregnant and paediatric patients in general radiography, fluoroscopy, computed tomography, mammography and dental radiology. It includes a comprehensive search of 83 documents from 32 countries and 6 international organisations over the last 39 years. In general, using shielding is recommended only under two conditions: if it does not compromise the diagnostic task and the performance of the procedure and/or if it reassures the patient and comforters that they are appropriately protected against potentially harmful effects of radiation. There are very few specific regulatory requirements to use shielding in a particular imaging modality, although they may consider use of shielding either as part of good radiological practice or as requirements for availability of protective or ancillary tools, without further specification of their use. There is a wide variety of positions among documents that recommend out-of-field shielding, those that do not recommend it and those that are not specific. Therefore, evidence-based consensus is still needed to ensure best and consistent practice.  相似文献   

14.
There is a relative paucity of recent information regarding the long-term health effects associated with exposure to ultrasound, and to infrasound and low-frequency noise (LFN). For ultrasound, further epidemiological studies are recommended, and priority should be given to studies investigating the effects of handedness and to studies assessing possible subtle effects on brain function. These studies should reflect contemporary practises in diagnostic ultrasound and have sufficiently long follow-up periods to examine the possibility of effects into late adolescence or beyond. In the absence of a non-exposed control group, it would be advisable to make comparisons between a highly exposed group with a less exposed group, and to compare groups exposed at differing gestational stages. The effects associated with ultrasound contrast agents should also be studied, and the appropriateness of the thermal index (TI) and mechanical index (MI) should be reviewed. It is recommended that animal models should be used to investigate the effects of exposure at differing gestational ages on development, and modern cellular and molecular techniques used to investigate potential mechanisms of interaction. Although explicit morphological changes have been reported following occupational and experimental exposures to infrasound and low LFN, it was recommended that a thorough review of the relevant biological and health effects literature was necessary before specific proposals could be made. Uncertainties about the characterisation of these low frequencies also indicated the need to develop appropriate measurement techniques and protocols.  相似文献   

15.
Plant phenology—the timing of cyclic or recurrent biological events in plants—offers insight into the ecology, evolution, and seasonality of plant‐mediated ecosystem processes. Traditionally studied phenologies are readily apparent, such as flowering events, germination timing, and season‐initiating budbreak. However, a broad range of phenologies that are fundamental to the ecology and evolution of plants, and to global biogeochemical cycles and climate change predictions, have been neglected because they are “cryptic”—that is, hidden from view (e.g., root production) or difficult to distinguish and interpret based on common measurements at typical scales of examination (e.g., leaf turnover in evergreen forests). We illustrate how capturing cryptic phenology can advance scientific understanding with two case studies: wood phenology in a deciduous forest of the northeastern USA and leaf phenology in tropical evergreen forests of Amazonia. Drawing on these case studies and other literature, we argue that conceptualizing and characterizing cryptic plant phenology is needed for understanding and accurate prediction at many scales from organisms to ecosystems. We recommend avenues of empirical and modeling research to accelerate discovery of cryptic phenological patterns, to understand their causes and consequences, and to represent these processes in terrestrial biosphere models.  相似文献   

16.
Recent technological and methodological advances have revolutionized wildlife monitoring. Although most biodiversity monitoring initiatives are geared towards focal species of conservation concern, researchers are increasingly studying entire communities, specifically the spatiotemporal drivers of community size and structure and interactions among species. This has resulted in the emergence of multi-species occupancy models (MSOMs) as a promising and efficient approach for the study of community ecology. Given the potential of MSOMs for conservation and management action, it is critical to know whether study design and model assumptions are consistent with inference objectives. This is especially true for studies that are designed for a focal species but can give insights about a community. Here, we review the recent literature on MSOMs, identify areas of improvement in the multi-species study workflow, and provide a reference model for best practices for focal species and community monitoring study design. We reviewed 92 studies published between 2009 and early 2018, spanning 27 countries and a variety of taxa. There is a consistent under-reporting of details that are central to determining the adequacy of designs for generating data that can be used to make inferences about community-level patterns of occupancy, including the spatial and temporal extent, types of detectors used, covariates considered, and choice of field methods and statistical tools. This reporting bias could consequently result in skewed estimates, affecting conservation actions and management plans. On the other hand, comprehensive reporting is likely to help researchers working on MSOMs assess the robustness of inferences, in addition to making strides in terms of reproducibility and reusability of data. We use our literature review to inform a roadmap with best practices for MSOM studies, from simulations to design considerations and reporting, for the collection of new data as well as those involving existing datasets.  相似文献   

17.

Background

Breastfeeding is viewed as the optimal method of infant feeding that provides many benefits to both the infant and the mother. The monitoring and reporting of breastfeeding indicators are essential for any country to plan and implement effective promotion programs for sustainable breastfeeding. The aim of this review is to examine the available studies and data on breastfeeding in Saudi Arabia, and determine the potential factors that affect breastfeeding practices and duration in this country.

Methods

The databases of Web of Knowledge, Science Direct and PubMed were searched using the relevant key words. Only studies that reported breastfeeding practices, rates and indicators in Saudi Arabia were included. Standard WHO definitions for breastfeeding categories were used in this review.

Results

Seventeen cross-sectional studies were identified and reviewed and five stated they used standard definitions. The self-administered questionnaire as a measurement tool was the predominant method of data collection. Infants' ages range from less than six months up to five years. Initiation rates were high (mostly above 90%), but a few studies reported low rates of timely initiation (within the first hour). The exclusive breastfeeding rate could not be accurately determined as rates range from 0.8% to 43.9% among studies due to the lack of clear definitions and the nature of study design. The partial (mixed) feeding method was common and the category of 'any breastfeeding' has generally high rates. The mean duration of breastfeeding has showed a progressive decline over time from 13.4 months in 1987 to 8.5 months in 2010. Factors associated with a high prevalence of breastfeeding and longer duration include increased maternal age, low educational levels, rural residence, low income, multiparity and avoiding contraceptives. The most common reason for breastfeeding cessation was insufficient breast milk. Other reasons include sickness, new pregnancy and breastfeeding problems.

Conclusions

Breastfeeding indicators in Saudi Arabia could not be monitored or compared relying on the available data because no longitudinal studies have been conducted in this country. A cohort study design would be the most appropriate procedure to rigorously assess and report valid results on breastfeeding practices and patterns in the Saudi society.  相似文献   

18.

Objectives

The aim of this study was to examine the relationships among maternal and infant characteristics, breastfeeding techniques, and exclusive breastfeeding initiation in different modes of birth using structural equation modeling approaches.

Methods

We examined a hypothetical model based on integrating concepts of a breastfeeding decision-making model, a breastfeeding initiation model, and a social cognitive theory among 952 mother-infant dyads. The LATCH breastfeeding assessment tool was used to evaluate breastfeeding techniques and two infant feeding categories were used (exclusive and non-exclusive breastfeeding).

Results

Structural equation models (SEM) showed that multiparity was significantly positively associated with breastfeeding techniques and the jaundice of an infant was significantly negatively related to exclusive breastfeeding initiation. A multigroup analysis in the SEM showed no difference between the caesarean section and vaginal delivery groups estimates of breastfeeding techniques on exclusive breastfeeding initiation. Breastfeeding techniques were significantly positively associated with exclusive breastfeeding initiation in the entire sample and in the vaginal deliveries group. However, breastfeeding techniques were not significantly associated with exclusive breastfeeding initiation in the cesarean section group. Maternal age, maternal race, gestations, birth weight of infant, and postnatal complications had no significant impacts on breastfeeding techniques or exclusive breastfeeding initiation in our study. Overall, the models fitted the data satisfactorily (GFI = 0.979–0.987; AGFI = 0.951–0.962; IFI = 0.958–0.962; CFI = 0.955–0.960, and RMSEA = 0.029–0.034).

Conclusions

Multiparity and jaundice of an infant were found to affect breastfeeding technique and exclusive breastfeeding initiation respectively. Breastfeeding technique was related to exclusive breastfeeding initiation according to the mode of birth. This relationship implies the importance of early effective interventions among first-time mothers with jaundice infants in improving breastfeeding techniques and promoting exclusive breastfeeding initiation.  相似文献   

19.
Molecular Biology Reports - This study aimed to investigate the association between biocides' reduced susceptibility and the presence of efflux pump genes including cepA, qacEΔ1 and qacE...  相似文献   

20.
With the aging population in Europe it is anticipated that the growing demand for blood products will not be met by the estimated supply. Therefore up-to-date recommendations for optimal administration of blood products in hemotherapy are needed. Ten years after the first meeting on optimal use of blood products at Wildbad Kreuth, Germany, a second symposium was organized to convene leading experts from the clinical, regulatory and economic perspective. The aim was to re-evaluate the existing state of hemotherapy, identify areas where further studies are needed, and to provide up-dated recommendations. A preparatory survey by questionnaire concerning guidelines, quality management in clinical use of blood products, provision of products in the individual countries and re-evaluation of the 1999 Wildbad Kreuth recommendations was completed in advance. The second Kreuth Meeting in April 2009 was attended by 110 experts in transfusion medicine, regulators and regulatory authorities from 38 countries. By consensus, 20 new recommendations were adopted. Most of the 1999 recommendations were found to still be valid 10 years later. But their realization and implementation on the levels of clinical practice, regulatory authorities and health policy decision makers is still lagging behind leaving an important task to accomplish. The Kreuth initiative toward optimal use of blood products should continue.  相似文献   

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