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PubMed2006

Spatial epidemiology of human schistosomiasis in Africa: risk models, transmission dynamics and control.

This paper reviews recent studies on the spatial epidemiology of human schistosomiasis in Africa. The integrated use of geographical information systems, remote sensing and geostatistics has provided new insights into the ecology and epidemiology of schistosomiasis at a variety of spatial scales. Because large-scale patterns of transmission are influenced by climatic conditions, an increasing number of studies have used remotely sensed environmental data to predict spatial distributions, most recently using Bayesian methods of inference. Such data-driven approaches allow for a more rational implementation of intervention strategies across the continent. It is suggested that improved incorporation of transmission dynamics into spatial models and assessment of uncertainties inherent in data and modelling approaches represent important future research directions.

Africa↗
PubMed2005

Changes in risk behavior and dynamics of hepatitis C virus infections among young drug users in Amsterdam, the Netherlands.

To elucidate the character and magnitude of the hepatitis C virus (HCV) epidemic among drug users in Amsterdam, 197 young drug users from the period 2000 to 2004 were compared with 215 counterparts from 1985 to 1989. Although injection risk behavior and HCV seroprevalence decreased sharply over time, HCV seroprevalence remains high (44%) among young drug users who have ever injected. Phylogenetic analysis shows that current HCV infections originate from diversification of strains already circulating in the past, but also from the recent introduction of new subtypes. HCV subtypes 1a and 3a remain the most prevalent among drug users in Amsterdam, but other subtypes such as 4d and 2b have entered the population. In conclusion, both the unpopularity of injecting drug use and the success of prevention campaigns are likely to be responsible for the decline in the seroprevalence of HCV and increased median time to seroconversion. Treatment of those infected chronically, in combination with the continuation of prevention programs, might decrease future HCV transmission.

Cohort Studies↗
PubMed1996

Aids, violence and behavioral coding: information theory, risk behavior and dynamic process on core-group sociogeographic networks.

Elsewhere we have presented a traveling-wave analysis of HIV transmission on a tightly self-interactive, geographically-focused core group social network (Wallace R. Soc. Sci. Med. 32, 847, 1991; Soc. Sci. Med. 33, 1155, 1991; Environ. Plan. A. 26, 767, 1994; Wallace R. and Fullilove M. Environ. Plan. A. 23, 1701 1991). Here we reanalyze the problem in probability space and recover a close analog of the Shannon Coding Theorem of information theory. Subsequent direct application of information-theoretic methods provides striking insight regarding the spread of disease along the sociogeographic networks of marginalized subgroups, suggesting that 'risk behaviors' for infection may constitute essential components of a behavioral code for the transmission of information within the noisy channel of a marginalized community's social networks. The code's form, including the incorporation of risk behaviors, arises as a direct consequence of the external oppressive forces which structure marginalization. This viewpoint suggests an explanation of the sometime-observed rapid transmission of both infection and of control strategies for infection along the same network, but suggests further that if risk behaviors are indeed parts of a behavioral code for the transmission of group norms, statements of individual worth or resource sharing, then high rates of relapse are inevitable, given the persistence of the external oppression which gives those behaviors symbolic value. We suggest that violent acts in particular may emerge as key behavioral symbols for 'sending a message' in socially disorganized communities, implying that school-based or other individual-oriented harm reduction strategies for violence prevention, in the absence of a comprehensive, multifactorial reform program, cannot significantly reverse the effects of continuing economic and social constraints or of public policies of planned shrinkage and benign neglect, factors primarily responsible for the disorganization of urban minority communities within the United States.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Exaggerated blood pressure response to dynamic exercise and risk of future hypertension.

This study examined the association between an exaggerated blood pressure response to treadmill exercise and the risk of developing hypertension. Subjects were healthy normotensive men (n = 5386) who had a baseline graded maximal exercise test between 1971 and 1982, and completed a mailed follow-up questionnaire. At follow-up in 1986, cases (n = 151) reported physician diagnosed hypertension and controls (n = 201) reported normotension. Those who had developed hypertension at follow-up were more likely to have had an exaggerated blood pressure response to exercise (OR = 2.4, 1.4-4.3). In multiple logistic regression analysis an exaggerated response was significantly associated (OR = 3.0, 1.5-6.1) with future hypertension after controlling for sitting systolic and diastolic blood pressure, weight change from age 21 to follow-up, entry age, family history of hypertension, body mass index, treadmill time, alcohol consumption, and years of follow-up. These results suggest that an exaggerated blood pressure response to exercise is independently associated with increased risk of future hypertension, and therefore, may be an important factor in determining hypertension risk.

Adult↗
PubMed1999

From a static to a dynamic concept of risk: the circadian epidemiology of cardiovascular events.

A growing body of evidence substantiates that the occurrence of cardiovascular events in unevenly distributed in time, especially during the 24 h. These temporal patterns are indicative of temporal variation in the (1) pathophysiological mechanisms that trigger cardiovascular events and (2) physiological status of the cardiovascular system, which combine to give rise to 24 h and other periodicities in the susceptibility to disease. The classic assumption of epidemiologic studies is constancy (or homeostasis) in one's risk to disease during the 24 h, as well as other, time domains. However, we propose a new concept, that of chronorisk since it takes into account the temporal variability in the pathophysiological mechanisms and their reciprocal temporal interactions that lead to day-night and other time-dependent patterns in cardiovascular events. This chronobiological approach, which is expected to contribute new insight into the prognostic and therapeutic assessment of cardiovascular events, is worthy of broader application in cardiovascular and other fields of medicine and warrants further investigation.

Cardiovascular Diseases↗
PubMed1999

Molecular characterization of rabies virus isolates from Mexico: implications for transmission dynamics and human risk.

Twenty-eight samples from humans and domestic and wild animals collected in Mexico between 1990 and 1995 were characterized by using anti-nucleoprotein monoclonal antibodies and limited sequence analysis of the nucleoprotein gene. The variants of rabies viruses identified in these samples were compared with other isolates from Mexico and the rest of the Americas to establish epidemiologic links between cases and outbreaks and to increase the understanding of rabies epidemiology in the Western Hemisphere. Antigenic and genetic diversity was found in all samples from dogs and dog-related cases, suggesting a long-term endemic situation with multiple, independent cycles of virus transmission. Two isolates from bobcats were antigenically and genetically homologous to the rabies variant circulating in the Arizona gray fox population, indicating a wider distribution of this variant than previously reported. Rabies isolates from skunks were unrelated to any variant analyzed in this study and represent a previously unrecognized cycle of rabies transmission in skunks in Baja California Sur. Two antigenic and genetic variants co-circulating in southern and eastern Mexico were found in viruses obtained from cases epidemiologically related to vampire bats. These results serve as a baseline for the better understanding of the molecular epidemiology of rabies in Mexico.

Animals↗
PubMed2001

[Dynamic surveillance of risk behaviors facilitating sexually transmitted disease/acquired immunodeficiency syndrome transmission among permanent residents in Kunming city in 1996-1999].

OBJECTIVE: To monitor the trends of risk behaviors promoting sexually transmitted disease/Acquired immunodeficiency syndrome (STD/AIDS) transmission among general public in order to develop appropriate intervention strategies and to evaluate impact of intervention programs. METHODS: Two hundred subjects were randomly selected and interviewed every other month in Kunming city from 1996 to 1999. STD-AIDS-related information on knowledge, attitudes and behavior were collected during the interview. RESULTS: The knowledge of STD and AIDS transmission increased from 49.2% to 62.8% (chi 2 = 96.5, P < 0.01) and from 16.6% to 35.2% (chi 2 = 146.5, P < 0.01), respectively. Knowledge on condom use and attitude to AIDS did not change much. Self-reported prevalence of risk behaviors remained low. Residents aged between 15 and 39 had unprotected sex behavior (0.8%-2.5%) and drug use (0.3%-2.4%). CONCLUSION: The awareness on STD and AIDS transmission increased gradually. Risk behavior of STD/HIV infection existed among residents aged between 15 and 39 years, which called for intervention programs in the future.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Exercise hypertension: behavior and the dynamic action of risk factors.

Epidemiological research identifies risk factors for coronary heart disease (CHD) to enable interventions to reduce the incidence of the disease. The twenty-year decline in cardiovascular-related deaths, however, cannot be explained solely by any pronounced changes in the classic risk factors (serum cholesterol, blood pressure and cigarette smoking) or related behaviors. Accordingly, it is apparent that there is much unexplained variance in the pathophysiology of CHD and that various behaviors are not associated with the classic risk factors in a simplistic fashion. Since acute and severe stress can affect thresholds for precipitation of cardiac events, the question of causality of long-term negative emotions has been repeatedly addressed; there is, however, no solid evidence that facets of neuroticism are related to documented acute coronary events while on the other hand, there is considerable evidence that emotionally maladjusted individuals have many complaints, including chest pain that is frequently labeled angina in spite of the absence of documented CHD. With regard to patterns of behavior in identifying risk factor status in CHD most attention has been focused on the Type A behavior pattern (hard-driving, job involvement, speed of activity, competitiveness, aggressiveness and mental and physical alertness). While this type of behavior has been related to clinical CHD independent of classic risk factors in some studies, the vast majority of epidemiological research has failed to replicate the association between the global Type A behavior pattern and any manifestation of CHD. Some attributes of the Type A behavior pattern, in particular, hostility, however, may be related to CHD even if the global pattern is not significantly associated.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1996

[The dynamics of the risk factors for IHD and the physical work capacity of the workers on locomotive teams based on the results of prospective observations].

The paper reports the results of a simultaneous study of muscular performance (MP) and main risk factors (RF) of ischemic heart disease (IHD) in 466 locomotive team members aged 30-49 free of IHD symptoms. A negative relationship has been established between MP and systolic, diastolic pressure, body mass. A 4-6-year follow-up of MP and IHD RF showed that MP improvement was associated with a trend to improvement in RF, while MP worsening entailed greater risk of IHD, especially in a group of 30-39-year-olds.

Adult↗
PubMed1990

Dynamic predictors of perioperative risk. Study of Perioperative Ischemia (SPI) Research Group.

Reduction in perioperative cardiac morbidity requires new approaches to the management of cardiac surgery patients or high-risk noncardiac surgery patients. Studies that have addressed the perioperative dynamic predictors of risk suggest a number of conclusions. Intraoperative hypotension and tachycardia appear to be risk factors for perioperative cardiac morbidity, whereas the role of hypertension remains controversial. It has recently been shown that ischemia occurring prior to bypass doubles or triples the risk of subsequent myocardial infarction. Electrocardiographic determination of ST segment depression is used as an indicator of ischemia, as are changes in ventricular filling pressure. Although increases in left ventricular end-diastolic pressure have proved to be reliable indicators of ischemia, changes in pulmonary capillary wedge pressure or pulmonary artery diastolic pressure have not. Perioperative segmental wall-motion or wall-thickening abnormalities appear to provide the most sensitive clinical measure of ischemia. Preliminary data also suggest that transesophageal echocardiographic wall-motion abnormalities may predict adverse outcome following cardiac surgery. Recent information regarding dynamic predictors of perioperative cardiac morbidity stresses the importance of the postoperative period.

California↗
PubMed2004

Considering the complexity of microbial community dynamics in food safety risk assessment.

The potential for competitive inhibition to limit the growth of microbial pathogens in food raises questions about the external validity of typical predictive microbiology studies and suggests the need to consider microbial community dynamics in food safety risk assessment. Ecological theory indicates, however, that community dynamics are highly complex and may be very sensitive to initial conditions and random variation. Seemingly incongruous empirical results for Escherichia coli O157:H7 in ground beef are shown to be consistent with a simple theoretical model of interspecific competition. A potential means of incorporating community-level microbial dynamics into the food safety risk assessment process is explored.

Antibiosis↗
PubMed1997

Comparison of electrocardiograms recorded with standard leads and derived from the vectorcardiographic frank leads in high risk patients.

Dynamic vectorcardiography (VCG) is increasingly employed for ischaemia monitoring with the use of a computerized method for recording and on-line analysis by the calculation of trend parameters. To elucidate how well the derived electrocardiogram (dECG), calculated from the VCG, compares with the simultaneously registered standard ECG (sECG), dECGs from 17 postoperative cardiac-risk patients and 36 subjects with acute myocardial infarction (AMI) were compared to sECGs, both quantitatively in leads II, III, V2 and V5 and qualitatively. Despite small, but some significant differences, mainly in the amplitudes of precordial leads, the qualitative interpretation by two independent cardiologists showed good agreement between the methods (kappa = 0.72 and 0.67, respectively) for the diagnosis of AMI/ischaemia. The dECG seems to be reliable and can be used clinically in these groups of patients during VCG recordings.

Aged↗
PubMed2006

A dynamical approach to evaluate risk in resource management.

With the depletion of many natural resources, we are growing aware of the need to understand the risks that stem from different management decisions. Here, we outline an approach to test the ability of different dynamical signatures to characterize time-series data: how likely is it that a natural population is declining, sustainable, or increasing, and at what rates are these temporal changes likely occurring? These dynamical signatures can serve as a robust foundation on which to formulate alternative scenarios in a decision analysis. They take account of much of the uncertainty in model parameters and have precise mathematical underpinnings with associated risks. We present methods to evaluate the likelihood of these scenarios, and ways that the analysis can be graphically represented. We discuss different ecological factors such as climate variability, life history, ecosystem interactions, and a changing population age structure, all of which impact the dynamics of natural populations. Considering the types of dynamical signatures that emerge from these factors can change our understanding of risk and the decisions that we make.

Decision Making, Organizational↗
PubMed1991

[Relation between coronary disease risk factors and mortality among men aged 40-59 years in the city of Frunze (5-year follow-up)].

The paper presents the dynamics of risk factors which was traced during prophylactic medical examinations and its relation to death rates among 40-59-year-old males from Frunze over 5 years. Prophylactic measures were found to lead to a positive dynamics of risk factors such as smoking, low physical activity, hypercholesterolemia, arterial hypertension in groups of active prevention. There was a decrease in death rates due to cardiovascular diseases, including myocardial infarction, stroke, among individuals with arterial hypertension, obesity, and low activity in the same group.

Adult↗
PubMed2006

Helical flow as fluid dynamic signature for atherogenesis risk in aortocoronary bypass. A numeric study.

The main purpose of the study was to verify if helical flow, widely observed in several vessels, might be a signature of the blood dynamics of vein graft anastomosis. We investigated the existence of a relationship between helical flow structures and vascular wall indexes of atherogenesis in aortocoronary bypass models with different geometric features. In particular, we checked for the existence of a relationship between the degree of helical motion and the magnitude of oscillating shear stress in conventional hand-sewn proximal anastomosis. The study is based on the numerical evaluation of four bypass geometries that are attached to a simplified computer representation of the ascending aorta with different angulations relative to aortic outflow. The finite volume technique was used to simulate realistic graft fluid dynamics, including aortic compliance and proper aortic and graft flow rates. A quantitative method was applied to evaluate the level of helicity in the flow field associated with the four bypass models under investigation. A linear inverse relationship (R = -0.97) was found between the oscillating shear index and the helical flow index for the models under investigation. The results obtained support the hypothesis that an arrangement of the flow field in helical patterns may elicit damping in wall shear stress temporal gradients at the proximal graft. Accordingly, helical flow might play a significant role in preventing plaque deposition or in tuning the mechanotransduction pathways of cells. Therefore, results confirm that helical flow constitutes an important flow signature in vessels, and its strength as a fluid dynamic index (for instance in combination with magnetic resonance imaging flow visualization techniques) for risk stratification, in the activation of both mechanical and biological pathways leading to fibrointimal hyperplasia.

Biomechanical Phenomena↗
PubMed2005

A proposed parent vessel geometry-based categorization of saccular intracranial aneurysms: computational flow dynamics analysis of the risk factors for lesion rupture.

OBJECT: The authors created a simple, broadly applicable classification of saccular intracranial aneurysms into three categories: sidewall (SW), sidewall with branching vessel (SWBV), and endwall (EW) according to the angiographically documented patterns of their parent arteries. Using computational flow dynamics analysis (CFDA) of simple models representing the three aneurysm categories, the authors analyzed geometry-related risk factors such as neck width, parent artery curvature, and angulation of the branching vessels. METHODS: The authors performed CFDAs of 68 aneurysmal geometric formations documented on angiograms that had been obtained in patients with 45 ruptured and 23 unruptured lesions. In successfully studied CFDA cases, the wall shear stress, blood velocity, and pressure maps were examined and correlated with aneurysm rupture points. Statistical analysis of the cases involving aneurysm rupture revealed a statistically significant correlation between aneurysm depth and both neck size (p < 0.0001) and caliber of draining arteries (p < 0.0001). Wider-necked aneurysms or those with wider-caliber draining vessels were found to be high-flow lesions that tended to rupture at larger sizes. Smaller-necked aneurysms or those with smaller-caliber draining vessels were found to be low-flow lesions that tended to rupture at smaller sizes. The incidence of ruptured aneurysms with an aspect ratio (depth/neck) exceeding 1.6 was 100% in the SW and SWBV categories, whereas the incidence was only 28.75% for the EW aneurysms. CONCLUSIONS: The application of standardized categories enables the comparison of results for various aneurysms' geometric formations, thus assisting in their management. The proposed classification system may provide a promising means of understanding the natural history of saccular intracranial aneurysms.

Aged↗