RESUMEN
The world's rural poor rely heavily on their immediate natural environment for subsistence and suffer high rates of morbidity and mortality from infectious diseases. We present a general framework for modelling subsistence and health of the rural poor by coupling simple dynamic models of population ecology with those for economic growth. The models show that feedbacks between the biological and economic systems can lead to a state of persistent poverty. Analyses of a wide range of specific systems under alternative assumptions show the existence of three possible regimes corresponding to a globally stable development equilibrium, a globally stable poverty equilibrium and bistability. Bistability consistently emerges as a property of generalized disease-economic systems for about a fifth of the feasible parameter space. The overall proportion of parameters leading to poverty is larger than that resulting in healthy/wealthy development. All the systems are found to be most sensitive to human disease parameters. The framework highlights feedbacks, processes and parameters that are important to measure in studies of rural poverty to identify effective pathways towards sustainable development.
Asunto(s)
Desarrollo Económico , Pobreza , Salud Pública , Población Rural , Conservación de los Recursos Naturales , Ecología , Humanos , Modelos Económicos , Modelos TeóricosRESUMEN
Understanding why some human populations remain persistently poor remains a significant challenge for both the social and natural sciences. The extremely poor are generally reliant on their immediate natural resource base for subsistence and suffer high rates of mortality due to parasitic and infectious diseases. Economists have developed a range of models to explain persistent poverty, often characterized as poverty traps, but these rarely account for complex biophysical processes. In this Essay, we argue that by coupling insights from ecology and economics, we can begin to model and understand the complex dynamics that underlie the generation and maintenance of poverty traps, which can then be used to inform analyses and possible intervention policies. To illustrate the utility of this approach, we present a simple coupled model of infectious diseases and economic growth, where poverty traps emerge from nonlinear relationships determined by the number of pathogens in the system. These nonlinearities are comparable to those often incorporated into poverty trap models in the economics literature, but, importantly, here the mechanism is anchored in core ecological principles. Coupled models of this sort could be usefully developed in many economically important biophysical systems--such as agriculture, fisheries, nutrition, and land use change--to serve as foundations for deeper explorations of how fundamental ecological processes influence structural poverty and economic development.
Asunto(s)
Desarrollo Económico , Dinámica Poblacional , Pobreza/economía , Medio Social , Enfermedades Transmisibles/economía , Conservación de los Recursos Naturales , Humanos , Modelos Teóricos , Factores SocioeconómicosRESUMEN
While most of the world is thought to be on long-term economic growth paths, more than one-sixth of the world is roughly as poor today as their ancestors were hundreds of years ago. The majority of the extremely poor live in the tropics. The latitudinal gradient in income is highly suggestive of underlying biophysical drivers, of which disease conditions are an especially salient example. However, conclusions have been confounded by the simultaneous causality between income and disease, in addition to potentially spurious relationships. We use a simultaneous equations model to estimate the relative effects of vector-borne and parasitic diseases (VBPDs) and income on each other, controlling for other factors. Our statistical model indicates that VBPDs have systematically affected economic development, evident in contemporary levels of per capita income. The burden of VBDPs is, in turn, determined by underlying ecological conditions. In particular, the model predicts it to rise as biodiversity falls. Through these positive effects on human health, the model thus identifies measurable economic benefits of biodiversity.
Asunto(s)
Biodiversidad , Renta , Enfermedades Parasitarias/economía , Enfermedades Parasitarias/epidemiología , Animales , Costo de Enfermedad , Vectores de Enfermedades , Geografía , Humanos , Modelos EstadísticosRESUMEN
While most of the world has enjoyed exponential economic growth, more than one-sixth of the world is today roughly as poor as their ancestors were many generations ago. Widely accepted general explanations for the persistence of such poverty have been elusive and are needed by the international development community. Building on a well-established model of human infectious diseases, we show how formally integrating simple economic and disease ecology models can naturally give rise to poverty traps, where initial economic and epidemiological conditions determine the long-term trajectory of the health and economic development of a society. This poverty trap may therefore be broken by improving health conditions of the population. More generally, we demonstrate that simple human ecological models can help explain broad patterns of modern economic organization.
Asunto(s)
Enfermedades Transmisibles/economía , Enfermedades Transmisibles/epidemiología , Modelos Biológicos , Pobreza , Humanos , Renta , PrevalenciaRESUMEN
BACKGROUND: Sentinel lymph node (SLN) mapping has become the standard of care for axillary staging in women with early-stage breast cancer. The purpose of the study was to investigate the hypothesis that nonvisualization of SLN on lymphoscintigraphy (LSG) predicts a subset of patients at risk of having a substantial burden of axillary tumor as evidenced by higher rate of lymph node involvement. STUDY DESIGN: We retrospectively reviewed the records of 1,500 patients who underwent dual-tracer SLN mapping for breast cancer between 1999 and 2004. LSG were reported as negative or positive. RESULTS: Ninety-one percent had axillary SLN(s) identified on LSG imaging. In 133 of 134 (99.3%) patients with a negative LSG, SLN(s) was identified intraoperatively either by blue dye or hand-held gamma detection. SLN was positive in 28.4% of LSG nonvisualized group and was positive in 29.1% of LSG visualized group (p>0.05). A significantly higher percentage of women older than 50 years of age had nonvisualization of SLN (p<0.0001). Body mass index (calculated as kg/m2) was >30 in 42.5% of LSG nonvisualized group and in 26.3% in LSG visualized group (p<0.0001). CONCLUSIONS: Failure to demonstrate axillary uptake by LSG appears to be related to technical factors and patient-related factors, such as body mass index and older age, but does not adversely affect SLN identification. The equivalent rate of positive SLNs in patients with a positive or negative LSG supports the null hypothesis that "failure to visualize" on LSG does not identify a subset of patients at higher risk of being axillary lymph node positive.
Asunto(s)
Neoplasias de la Mama/patología , Ganglios Linfáticos/diagnóstico por imagen , Ganglios Linfáticos/patología , Adulto , Anciano , Anciano de 80 o más Años , Axila , Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/cirugía , Femenino , Humanos , Persona de Mediana Edad , Estadificación de Neoplasias , Valor Predictivo de las Pruebas , Cintigrafía , Estudios Retrospectivos , Biopsia del Ganglio Linfático CentinelaRESUMEN
BACKGROUNDS AND OBJECTIVES: Open (OT) and percutaneous closed (PCT) techniques have been described for placement of the MammoSite catheter to deliver accelerated partial breast brachytherapy. We report early complications of both techniques. METHODS: A total of 125 patients underwent catheter placement for MammoSite high-dose rate brachytherapy, with 108 patients successfully completing treatment. The OT was used in 85 patients and PCT in 40 patients. The mean distance between the balloon surface and breast skin was 1.44 cm and 1.31 cm, respectively. Average skin dose was 278 cGy in the OT group and 295 cGy in the PCT group (P > 0.05). Average gross specimen size was 43.16 cm3 in the OT group and 62.19 cm3 in the PCT group. Median follow-up was 11 months for the OT group and 5 months for the PCT group. RESULTS: In 17 cases, the catheter was subsequently removed without the patient completing treatment. Two of the patients in the OT group (3%) developed a delayed abscess. The overall incidence of persistent seroma (>6 months) was 20% with all occurring in the OT group, 30% of those patients. There were no acute skin toxicities higher than grade 2. The overall cosmesis is excellent or good in 95% of patients. CONCLUSION: Despite short follow-up and a small sample size in this study, it seems that the MammoSite brachytherapy was well tolerated by patients with early stage breast cancer when using either the OT or PCT.
Asunto(s)
Braquiterapia/instrumentación , Braquiterapia/métodos , Neoplasias de la Mama/radioterapia , Anciano , Anciano de 80 o más Años , Braquiterapia/efectos adversos , Neoplasias de la Mama/cirugía , Carcinoma in Situ/patología , Carcinoma in Situ/radioterapia , Carcinoma Ductal/radioterapia , Femenino , Humanos , Persona de Mediana Edad , Invasividad Neoplásica , Estadificación de Neoplasias , Reoperación , Resultado del TratamientoRESUMEN
Core needle biopsy (CNB) is used to sample both mammographically and ultrasound detected breast lesions. A diagnosis of ductal carcinoma in situ (DCIS) by CNB does not ensure the absence of invasive cancer upon surgical excision and as a result an upstaged patient may need to undergo additional surgery for axillary nodal evaluation. This study evaluates the accuracy of CNB in excluding invasive disease and the preoperative features that predict upstaging of DCIS to invasive breast cancer. Two hundred fifty-four patients over an 8-year period from 1994 to 2002 with a diagnosis of DCIS alone by CNB were retrospectively reviewed. Underestimation of invasive cancer by CNB was determined. Radiographic, pathologic, and surgical features of the cohort were compared using univariate and multivariate analysis. The mean age was 55 years (range 27-84) and mean follow-up was 25 months with one patient unavailable for follow-up. There were a total of six patient deaths, all of which were not disease-specific. A total of 21 out of 254 patients (8%) with DCIS by CNB were upstaged to invasive cancer following surgical excision. There was a significant inverse relationship between the number of core biopsies and the incidence of upstaging (p < 0.006) in that patients with fewer core samples were more likely to be upstaged at surgical pathology. No relationship was noted between the size of the core samples and the likelihood of upstaging (p > 0.4). Of 21 patients with invasion, all but two had comedonecrosis by CNB. Comedonecrosis by CNB significantly increased the likelihood of upstaging (p < 0.001). Of the 21 patients who were upstaged, 12 required subsequent surgery for nodal evaluation while nine had sentinel node biopsy at initial operation. Finally, upstaged patients were significantly more likely to have a positive margin (p < 0.008). Ductal carcinoma in situ with comedonecrosis on CNB can help to predict the possibility of invasion. Increasing the number of core biopsies reduced the likelihood of sampling error.
Asunto(s)
Biopsia con Aguja , Neoplasias de la Mama/patología , Carcinoma Intraductal no Infiltrante/patología , Carcinoma Intraductal no Infiltrante/secundario , Lesiones Precancerosas/patología , Adulto , Anciano , Femenino , Estudios de Seguimiento , Humanos , Metástasis Linfática , Persona de Mediana Edad , Invasividad Neoplásica , Neoplasia Residual , Examen Físico , Valor Predictivo de las Pruebas , Estudios RetrospectivosRESUMEN
INTRODUCTION: The routine use of sentinel node biopsy (SLNB) at the time of prophylactic mastectomy remains controversial. This retrospective study was undertaken to determine if SLNB is justified in patients undergoing CPM. METHODS: Between 1999 and 2004, 155 patients underwent contralateral prophylactic mastectomy (CPM) at the Magee-Womens Hospital of University of Pittsburgh Medical Center. Eighty patients (51.6%) had SLNB performed at the time of CPM. The therapeutic mastectomy and the CPM specimens were evaluated for histopathology. Goldflam's classification was used to determine the risk of malignancy in the CPM specimens. RESULTS: Pathology in the therapeutic mastectomy specimens included 105 (68%) invasive carcinomas and 50 (32%) in-situ carcinomas. Multicentricity and/or multifocality were reported in 49.7%, and 70% were estrogen receptor positive. Two invasive breast cancers and three cases of DCIS were diagnosed in 155 CPM specimens (n = 5, 3.2%). The median number of SLN identified was 2 (range 1-6) from the CPM axilla. Two patients had positive SLNB for metastatic carcinoma (n = 2/80, 2.5%) with no primary tumor identified in the prophylactic mastectomy specimen. In both patients the therapeutic mastectomy was for recurrent invasive carcinoma in patients with a prior history of axillary node dissection. Occult carcinoma was found in five prophylactic mastectomy specimens: two invasive and three DCIS. Only 1 out of the 75 patients not undergoing SLNB at the time of their initial surgery would have required axillary staging for a previously undiagnosed invasive cancer in the CPM specimen on final pathology. Of all 155 patients undergoing CPM, only 4 (2.5%) had identified final pathologic findings where axillary staging with SLNB was beneficial. There was no evidence of arm lymphedema in any patient who had undergone CPM and SLNB at a median follow-up of 24 months. CONCLUSION: Although SLNB is a minimally invasive method of axillary staging, this retrospective study does not support its routine use in patients undergoing CPM.
Asunto(s)
Neoplasias de la Mama/patología , Neoplasias de la Mama/cirugía , Biopsia del Ganglio Linfático Centinela , Adulto , Anciano , Carcinoma Ductal de Mama/patología , Carcinoma Ductal de Mama/cirugía , Carcinoma Lobular/patología , Carcinoma Lobular/cirugía , Femenino , Humanos , Mastectomía , Persona de Mediana Edad , Estudios RetrospectivosRESUMEN
BACKGROUND AND OBJECTIVES: Preemptive analgesia is the concept of providing analgesia before surgical incision, resulting in less postoperative pain. The purpose of this study is to determine if preemptive and/or postoperative local anesthetic infiltration of bupivacaine in patients undergoing segmental mastectomy results in less postoperative pain compared with patients receiving placebo. METHODS: In this prospective, double-blinded study, 120 patients were randomized into 4 groups: group 1, preincisional (10 mL) and postoperative (10 mL) wound infiltration of 0.5% bupivicaine, (+Pre+Post); group 2, preincisional bupivacaine (10 mL) and postoperative infiltration (10 mL) of placebo (normal saline solution), (+Pre-Post); group 3, preincisional placebo (10 mL) and postoperative bupivacaine (10 mL), (-Pre+Post); or group 4, preincisional (10 mL) and postoperative infiltration of placebo (10 mL), (-Pre-Post). All patients received a standardized laryngeal mask general anesthetic. Data were recorded at the following time intervals: preoperative admission, postanesthesia care unit (PACU) admission, PACU stay, stepdown-unit admission, stepdown-unit stay, hospital discharge, and 24 hours post operation. RESULTS: No difference was noted with respect to preoperative pain visual analog scale (VAS, 0-100 mm), surgical duration, PACU stay time, stepdown-unit stay time, incidence of postoperative nausea, or treatment for nausea in all measured time periods. The placebo group (group 4) had significantly higher mean pain VAS scores during the early postoperative period (PACU admission and PACU stay) compared to the other groups (PACU admission: group 1 = 2 +/- 8, group 2 = 4 +/- 11, group 3 = 3 +/- 15, group 4 = 17 +/- 21, P < .01; PACU stay: group 1 = 6 +/- 13, group 2 = 6 +/- 10, group 3 = 10 +/- 21, group 4 = 20 +/- 18, P < .01). Likewise, the number of patients who reported pain (pain frequency) was significantly higher in group 4 (placebo) compared with all other groups at PACU admission, PACU stay, stepdown-unit admission, and stepdown-unit stay (P < or = .01). CONCLUSION: Preincisional and/or postoperative wound bupivacaine infiltration lacks preemptive analgesic effects for segmental mastectomy.
Asunto(s)
Analgésicos/administración & dosificación , Anestésicos Locales/administración & dosificación , Bupivacaína/administración & dosificación , Mastectomía Segmentaria , Dolor Postoperatorio/prevención & control , Medicación Preanestésica , Método Doble Ciego , Femenino , Humanos , Persona de Mediana Edad , Dimensión del Dolor , Cuidados Posoperatorios , Estudios ProspectivosRESUMEN
There is growing evidence that communicable diseases constitute a strong selective force on the evolution of social systems. It has been suggested that infectious diseases may determine upper limits of host sociality by, for example, inducing territoriality or early juvenile dispersal. Here we use game theory to model the evolution of host sociality in the context of communicable diseases. Our model is then augmented with the evolution of virulence to determine coevolutionarily stable strategies of host sociality and pathogen virulence. In contrast to a controversial hypothesis by Ewald (1994), our analysis indicates that pathogens may become more virulent when contact rates are low, and their prevalence can ultimately induce greater sociality.
Asunto(s)
Evolución Biológica , Enfermedades Transmisibles/epidemiología , Modelos Teóricos , Prevalencia , Conducta Social , Simulación por Computador , Teoría del Juego , VirulenciaRESUMEN
BACKGROUND: Routine intraoperative evaluation of sentinel lymph nodes (SLNs) in breast cancer suffers from lack of sensitivity and consumes both time and resources. Failure to perform immediate consultation requires node-positive patients to return for delayed dissection. METHODS: We sought to determine whether selective use of intraoperative pathology consultation (IOC), based on the surgeon's clinical suspicion for metastases, would be accurate, avoid unnecessary consultations, and have a similar rate of delayed axillary dissection. We performed a retrospective chart review of two cohorts of clinically node-negative patients with invasive breast cancer undergoing axillary lymph node dissection (ALND). Selective pathology evaluation was performed in the study group and mandatory evaluation in the control group. RESULTS: The axillary basins of 327 patients undergoing routine IOC were compared with those of 91 patients in whom selective IOCs were requested. Twenty-eight consultations (31%) were obtained in the selective group. Selective consultation changed intraoperative management in 11 of 28 patients (39%) compared to 46 of 327 (14%) in the routine group (P = 0.005). The mean SLN metastasis size was 9.6 mm compared to 1.5 mm in patients in whom consultation was deferred (P = 0.003). The need for delayed ALND (17% vs. 14%) was similar in both groups, and was determined by occult metastases that were not detected by either method. CONCLUSIONS: Selective use of IOC detects the majority of SLN macrometastases, avoids consultation that does not alter intraoperative management, and is not associated with an increased need for delayed ALND.