GAMLSS for high-variability data: an application to liver fibrosis case

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Andrea Marletta ◽  
Mariangela Sciandra
Keyword(s):  
Risk Factors ◽  
Liver Fibrosis ◽  
Statistical Models ◽  
Generalized Additive Model ◽  
Additive Model ◽  
Finite Mixture Model ◽  
High Variability ◽  
Finite Mixture ◽  
Potential Risk Factors ◽  
Variability Data

AbstractThis article aims to provide rigorous and convenient statistical models for dealing with high-variability phenomena. The presence of discrepance in variance represents a substantial issue when it is not possible to reduce variability before analysing the data, leading to the possibility to estimate an inadequate model. In this paper, the application of Generalized Additive Model for Location, Scale and Shape (GAMLSS) and the use of finite mixture model for GAMLSS will be proposed as a solution to the problem of overdispersion. An application to Liver fibrosis data is illustrated in order to identify potential risk factors for patients, which could determine the presence of the disease but also its levels of severity.

scholarly journals Modelling Cyclists’ Multi-Exposure to Air and Noise Pollution with Low-Cost Sensors—The Case of Paris

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 422
Author(s):  
Jérémy Gelb ◽  
Philippe Apparicio
Keyword(s):  
Statistical Models ◽  
Noise Exposure ◽  
Generalized Additive Model ◽  
Low Cost ◽  
Additive Model ◽  
Noise Pollution ◽  
Ventilation Rate ◽  
Mixed Effects ◽  
Mobile Data ◽  
Mobile Data Collection

Cyclists are particularly exposed to air and noise pollution because of their higher ventilation rate and their proximity to traffic. However, few studies have investigated their multi-exposure and have taken into account its real complexity in building statistical models (nonlinearity, pseudo replication, autocorrelation, etc.). We propose here to model cyclists’ exposure to air and noise pollution simultaneously in Paris (France). Specifically, the purpose of this study is to develop a methodology based on an extensive mobile data collection using low-cost sensors to determine which factors of the urban micro-scale environment contribute to cyclists’ multi-exposure and to what extent. To this end, we developed a conceptual framework to define cyclists’ multi-exposure and applied it to a multivariate generalized additive model with mixed effects and temporal autocorrelation. The results show that it is possible to reduce cyclists’ multi-exposure by adapting the planning and development practices of cycling infrastructure, and that this reduction can be substantial for noise exposure.

scholarly journals Ambient Sulfate Trends and the Influence of Meteorology

2005 ◽  
Vol 44 (11) ◽  
pp. 1745-1760 ◽  
Author(s):  
Stephen F. Mueller
Keyword(s):  
Statistical Models ◽  
Generalized Additive Model ◽  
Additive Model ◽  
Total Sulfur ◽  
Eastern United States ◽  
Sulfur Species ◽  
Sulfate Sulfur ◽  
Average Change ◽  
Meteorological Influences ◽  
Local Deposition

Abstract Data on atmospheric levels of sulfur dioxide (SO2) and sulfate were examined to quantify changes since 1989. Changes in sulfur species were adjusted to account for meteorological variability. Adjustments were made using meteorological variables expressed in terms of their principal components that were used as predictors in statistical models. Several models were tested. A generalized additive model (GAM)—based in part on nonparametric, locally smoothed predictor functions—computed the greatest association between sulfate and the meteorological predictors. Sulfate trends estimated after a GAM-based adjustment for weather-related influences were found to be primarily downward across the eastern United States by as much as 6.7% per year (average of −2.6% per year), but large spatial variability was noted. The most conspicuous characteristic in the trends was over portions of the Appalachian Mountains where very small (average = −1.6% per year) and often insignificant sulfate changes were found. The Appalachian region also experienced a tendency, after removing meteorological influences, for increases in the ratio RS of sulfate sulfur to total sulfur. Before 1991, this ratio averaged 0.33 across all sites. Appalachian increases in RS were equivalent to 0.07 during 1989–2001 (significant for most sites at the 0.05 level), or nearly 2 times the average change at the other sites. This suggests that conditions over the Appalachians became notably more efficient at oxidizing SO2 into sulfate. Alternatively, subtle changes in local deposition patterns occurred, preferentially in and near mountainous monitoring sites, that changed the SO2–sulfate balance.

scholarly journals Age at Smoking Onset and Risk of Heavy Cigarette Smoking Among Iranian Adult Male: An Application of Generalized Additive Model

2021 ◽  
Author(s):  
Zohreh Manoochehri ◽  
Javad Faradmal ◽  
Abbas Moghimbeigi
Keyword(s):  
Risk Factors ◽  
Generalized Additive Model ◽  
Age Of Onset ◽  
Communicable Disease ◽  
Additive Model ◽  
Cross Sectional Survey ◽  
Heavy Smoking ◽  
Smoking Intensity ◽  
The Relationship ◽  
Heavy Smokers

Abstract Background: Because the age at which a person first starts smoking has such a strong correlation with future smoking behaviours, it's crucial to examine its relationship with smoking intensity. However, it is still challenging to accurately identify this relationship due to limitations in the methodology of the performed studies .Therefore the main purpose of this study is to evaluate this relationship and also to identify the other risk factors affecting smoking intensity using an appropriate model.Methods: Data from 913 Iranian male current smokers over the age of 18 was evaluated from a national cross-sectional survey of non-communicable disease (NCD) risk factors in 2016. Individuals were classified into: light, moderate, and heavy smokers. A generalized additive model (GAM) was used to assess the relationship.Results: 246 (26.9%) subjects were light smokers, 190 (20.8%) subjects were moderate smokers and 477 (52.2%) subjects were heavy smokers. According to the GAM results, the relationship was nonlinear and smokers who started smoking at a younger age were more likely to become heavy smokers. The factors of unemployment (OR = 1.364), retirement (OR = 1.217), and exposure to secondhand smoke at home (OR = 1.364) increased the risk of heavy smoking. but, smokers with high-income (OR = 0.742) had a low tendency to heavy smoking. Conclusions: GAM identified the nonlinear relationship between the age of onset of smoking and smoking intensity. Tobacco control programs should be focused on young and adolescent groups and poorer socio-economic communities.

scholarly journals Learning Dyadic Data and Predicting Unaccomplished Co-Occurrent Values by Mixture Model

2020 ◽  
Author(s):  
Loc Nguyen
Keyword(s):  
Statistical Model ◽  
Mixture Model ◽  
Expectation Maximization ◽  
Statistical Models ◽  
Random Variable ◽  
Finite Mixture Model ◽  
Finite Mixture ◽  
Dyadic Data ◽  
A Value ◽  
Occurrence Data

Dyadic data which is also called co-occurrence data (COD) contains co-occurrences of objects. Searching for statistical models to represent dyadic data is necessary. Fortunately, finite mixture model is a solid statistical model to learn and make inference on dyadic data because mixture model is built smoothly and reliably by expectation maximization (EM) algorithm which is suitable to inherent spareness of dyadic data. This research summarizes mixture models for dyadic data. When each co-occurrence in dyadic data is associated with a value, there are many unaccomplished values because a lot of co-occurrences are inexistent. In this research, these unaccomplished values are estimated as mean (expectation) of random variable given partial probabilistic distributions inside dyadic mixture model.

scholarly journals CLIMATE-DRIVEN STATISTICAL MODELS AS EFECTIVE PREDICTIONS OF LOCAL DENGUE INDICENCE IN COSTA RICA: A GENERALIZED ADDITIVE MODEL AND RANDOM FOREST APPROACH

2019 ◽  
Vol 27 (1) ◽  
pp. 1-21
Author(s):  
PAOLA VÁSQUEZ ◽  
ANTONIO LORÍA ◽  
FABIO SÁNCHEZ ◽  
LUIS ALBERTO BARBOZA
Keyword(s):  
Public Health ◽  
Relative Risk ◽  
Costa Rica ◽  
Random Forest ◽  
Prediction Model ◽  
Statistical Models ◽  
Generalized Additive Model ◽  
Additive Model ◽  
Climate Data ◽  
Tropical Country

Climate has been an important factor in shaping the distribution and incidence of dengue cases in tropical and subtropical countries. In Costa Rica, a tropical country with distinctive micro-climates, dengue has been endemic since its introduction in 1993, inflicting substantial economic, social, and public health repercussions. Using the number of dengue reported cases and climate data from 2007-2017, we fitted a prediction model applying a Generalized Additive Model (GAM) and Random Forest (RF) approach, which allowed us to retrospectively predict the relative risk of dengue in five climatological diverse municipalities around the country.

scholarly journals A Simulation Study to Evaluate Survey Designs and Assessment Models for Estimation of Dungeness Crab (Cancer magister) Softshell Periods

2016 ◽  
Vol 9 (1) ◽  
pp. 57-74
Author(s):  
Zane Zhang ◽  
Jason S. Dunham
Keyword(s):  
Data Collection ◽  
Hierarchical Model ◽  
Statistical Models ◽  
Generalized Additive Model ◽  
Additive Model ◽  
Quadratic Function ◽  
Dungeness Crab ◽  
Catch Per Unit Effort ◽  
Unit Effort ◽  
Survey Designs

Softshell Dungeness Crabs have inferior meat quality and are vulnerable to handling by harvesters; therefore, knowing when softshell periods occur is important for managing Dungeness Crab fisheries. A computer simulation was used to study the effectiveness of several survey designs and statistical models for estimating softshell periods which normally would be construed from crab shell condition data obtained from trap surveys. Survey designs varied in the number of years of data collection (1, 3, 5 or 10 years) and by the number and arrangement of sampling events per year. Three statistical models, including standardized catch-per-unit-effort (SCPUE), hierarchical, and generalized additive, were tested using catch-per-unit-effort data (CPUEs) or CPUE- transformed data. CPUEs were standardised by dividing CPUE estimates by the maximum CPUE obtained in the sample year, and then transformed using the complementary log-log function. In the hierarchical model, CPUEs were modelled using a lognormal distribution, assuming the expected logarithms of CPUEs are a quadratic function of days plus a random normal error. CPUE-transformed data were modelled using a normal distribution, assuming expected values are a quadratic function of days in the SCPUE model or a spline smooth function of days in the generalized additive model. Results suggest the best survey design requires a relatively high number (6 or 11) of sampling events during several key consecutive months which contain the softshell period, and fewer sampling events during those months when softshell crab abundance is low. A minimum 3 years of data collection is required to produce reliable outputs. The hierarchical model performs best, slightly better than the SCPUE model. Use of the generalized additive model is not recommended.

Premature Arterial Disease Associated with Familial Antithrombin III Deficiency

1990 ◽  
Vol 63 (01) ◽  
pp. 013-015 ◽  
Author(s):  
E J Johnson ◽  
C R M Prentice ◽  
L A Parapia
Keyword(s):  
Risk Factors ◽  
Venous Thromboembolism ◽  
Potential Risk ◽  
Antithrombin Iii ◽  
Arterial Disease ◽  
Coagulation System ◽  
Early Age ◽  
Arterial Thromboembolism ◽  
Potential Risk Factors ◽  
Antithrombin Iii Deficiency

SummaryAntithrombin III (ATIII) deficiency is one of the few known abnormalities of the coagulation system known to predispose to venous thromboembolism but its relation to arterial disease is not established. We describe two related patients with this disorder, both of whom suffered arterial thrombotic events, at an early age. Both patients had other potential risk factors, though these would normally be considered unlikely to lead to such catastrophic events at such an age. Thrombosis due to ATIII deficiency is potentially preventable, and this diagnosis should be sought more frequently in patients with arterial thromboembolism, particularly if occurring at a young age. In addition, in patients with known ATIII deficiency, other risk factors for arterial disease should be eliminated, if possible. In particular, these patients should be counselled against smoking.

Staphylococcus aureus nasal colonization among Vietnamese adults: prevalence, risk factors and antibiotic susceptibility profile

MedPharmRes ◽  
2018 ◽  
Vol 2 (2) ◽  
pp. 21-31
Author(s):  
Nguyen Phan ◽  
Hien Pham ◽  
Thuc Nguyen ◽  
Hoai Nguyen
Keyword(s):  
Risk Factors ◽  
Staphylococcus Aureus ◽  
Antibiotic Susceptibility ◽  
Nasal Carriage ◽  
Resistance Rate ◽  
High Rate ◽  
Weight History ◽  
Potential Risk Factors ◽  
History Of ◽  
Vietnamese Community

Staphylococcus aureus (S. aureus) has long been recognized as an important human pathogen causing many severe diseases. It is also a part of human normal flora with its ecological niche in the human anterior nares. This study focused on screening S. aureus nasal carriage in community and its relationship to human physiological and pathological factors which have not been studied in Vietnam previously. Two hundred and five volunteers in Ho Chi Minh City from 18 to 35 and over 59 years old both male and female participated in the study. Result showed that the prevalence of S. aureus nasal carriage in southern Vietnamese community was relatively low, only 11.2% (23/205), much lower than that in other international reports on human S. aureus. In addition, nasal carriage of the older age group (> 59 years old, 13.7%) was higher than that of younger age (18-35 years old, 10.4%). Other potential risk factors such as gender, career, height, weight, history of antibiotic usage, daily nasal wash, use of nasal medication sprays, acne problems, smoking and nasal problems showed no significant impact on S. aureus carriage. The obtained S. aureus nasal isolates were all sensitive to vancomycin. Lincomycin and tetracycline had low resistance rate with 4.3 % and 17.4 %, respectively. However, the isolates showed particularly high rate of multidrug resistance (54.2%) In summary, our data provided researchers an overview on S. aureus nasal carriage and antibiotic susceptibility profile of the community- isolated S. aureus in Vietnam. This would serve as valuable information on assessing risk of community-acquired S. aureus infections.

Sign in / Sign up

Export Citation Format

Share Document