Statistical learning techniques applied to epidemiology: a simulated case-control comparison study with logistic regression

<p>Abstract</p> <p>Background</p> <p>When investigating covariate interactions and group associations with standard regression analyses, the relationship between the response variable and exposure may be difficult to characterize. When the relationship is nonlinear, linear modeling techniques do not capture the nonlinear information content. Statistical learning (SL) techniques with kernels are capable of addressing nonlinear problems without making parametric assumptions. However, these techniques do not produce findings relevant for epidemiologic interpretations. A simulated case-control study was used to contrast the information embedding characteristics and separation boundaries produced by a specific SL technique with logistic regression (LR) modeling representing a parametric approach. The SL technique was comprised of a kernel mapping in combination with a perceptron neural network. Because the LR model has an important epidemiologic interpretation, the SL method was modified to produce the analogous interpretation and generate odds ratios for comparison.</p> <p>Results</p> <p>The SL approach is capable of generating odds ratios for main effects and risk factor interactions that better capture nonlinear relationships between exposure variables and outcome in comparison with LR.</p> <p>Conclusions</p> <p>The integration of SL methods in epidemiology may improve both the understanding and interpretation of complex exposure/disease relationships.</p

A spatial approach for the epidemiology of antibiotic use and resistance in community-based studies: the emergence of urban clusters of Escherichia coli quinolone resistance in Sao Paulo, Brasil

Copyright © Kiffer et al; licensee BioMed Central Ltd. 2011 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background Population antimicrobial use may influence resistance emergence. Resistance is an ecological phenomenon due to potential transmissibility. We investigated spatial and temporal patterns of ciprofloxacin (CIP) population consumption related to E. coli resistance emergence and dissemination in a major Brazilian city. A total of 4,372 urinary tract infection E. coli cases, with 723 CIP resistant, were identified in 2002 from two outpatient centres. Cases were address geocoded in a digital map. Raw CIP consumption data was transformed into usage density in DDDs by CIP selling points influence zones determination. A stochastic model coupled with a Geographical Information System was applied for relating resistance and usage density and for detecting city areas of high/low resistance risk. Results E. coli CIP resistant cluster emergence was detected and significantly related to usage density at a level of 5 to 9 CIP DDDs. There were clustered hot-spots and a significant global spatial variation in the residual resistance risk after allowing for usage density. Conclusions There were clustered hot-spots and a significant global spatial variation in the residual resistance risk after allowing for usage density. The usage density of 5-9 CIP DDDs per 1,000 inhabitants within the same influence zone was the resistance triggering level. This level led to E. coli resistance clustering, proving that individual resistance emergence and dissemination was affected by antimicrobial population consumption

The historical origins of corruption in the developing world: a comparative analysis of East Asia

A new approach has emerged in the literature on corruption in the developing world that breaks with the assumption that corruption is driven by individualistic self-interest and, instead, conceptualizes corruption as an informal system of norms and practices. While this emerging neo-institutionalist approach has done much to further our understanding of corruption in the developing world, one key question has received relatively little attention: how do we explain differences in the institutionalization of corruption between developing countries? The paper here addresses this question through a systematic comparison of seven developing and newly industrialized countries in East Asia. The argument that emerges through this analysis is that historical sequencing mattered: countries in which the "political marketplace" had gone through a process of concentration before universal suffrage was introduced are now marked by less harmful types of corruption than countries where mass voting rights where rolled out in a context of fragmented political marketplaces. The paper concludes by demonstrating that this argument can be generalized to the developing world as a whole

The relationship between cerebral blood flow velocity fluctuations and sleep state in normal newborns.

Cerebral blood flow velocity was recorded for an average of 23 4-min epochs during natural sleep in 11 normal full-term newborn babies. Intracranial pressure, core temperature, and respiration were simultaneously and non-invasively monitored. Sleep state was classified using information from EEG, pattern of respiration, and eye and body movements by a trained observer. From a total of 238 epochs, 66 were considered to occur in quiet sleep, 101 in active sleep, and in 77 the baby was awake, in a transitional state or moving excessively. Slow cyclical variations in cerebral blood flow velocity were observed with a frequency of between 2 and 6 cycles/min, and these were of significantly greater amplitude during quiet sleep (24%) compared to active sleep (16%; p < 0.0001, Mann Whitney U test). There was no difference in median cerebral blood flow velocity (7.5 cm/s). The cyclical variation observed in normal babies were similar to those described in preterm babies and adults, at a similar frequency to B waves in intracranial pressure. They may represent vasomotor waves in the small autoregulatory arteries of the brain. Reduction in sensitivity of the receptors initiating the waves may occur in active sleep or there may be competition from other oscillatory mechanisms

Dentate gyrus microstructure is associated with resilience after exposure to maternal stress across two human cohorts

Background: Maternal stress (MS) is a well-documented risk factor for impaired emotional development in offspring. Rodent models implicate the dentate gyrus (DG) of the hippocampus in the effects of MS on offspring depressive-like behaviors, but mechanisms in humans remain unclear. Here, we test across two independent cohorts whether MS is associated with depressive symptoms and with DG micro- and macro-structural alterations in offspring. Methods: We analyzed DG DTI mean diffusivity (DG-MD) and volume in a 3-Generation Family Risk for Depression study (TGS; n=69, mean age 35.0) and the Adolescent Brain Cognitive Development Study (ABCD; n=5196, mean age 9.9) using generalized estimating equation models and mediation analysis. MS was assessed by the Parenting Stress Index (in TGS) and a measure compiled from the Adult Response Survey (ABCD). PHQ-9 and rumination scales (TGS) and Child Behavior Checklist (ABCD) measured offspring depressive symptoms at follow-up. Schedule for Affective Disorders and Schizophrenia–Lifetime interview measured depression diagnoses. Results: Across cohorts, MS was associated with future symptoms and higher DG-MD (indicating disrupted microstructure) in offspring. Higher DG-MD was associated with higher symptom scores measured 5 years (TGS) and 1-year (ABCD) after MRI. In ABCD, DG-MD is increased in high-MS offspring who have depressive symptoms at follow-up, but not in offspring who remain resilient or whose mother had low MS. Conclusions: Converging results across two independent samples extend previous rodent studies and suggest a role for the DG in exposure to MS and offspring depression

Tracking the dynamics of T-cell activation in response to Salmonella infection

Despite the current availability of Salmonella vaccines, typhoid fever remains a significant public health problem in developing countries. A greater understanding of T-cell activation and the development of immunological memory during Salmonella infection should lead to the development of more effective prophylactic intervention. Here, we review recent literature on the initiation, expansion and memory development of T-cell responses using the mouse model of typhoid. We pay particular attention to strategies for tracking T-cell responses in vivo and ex vivo, and suggest models to integrate some these studies