Development of methods for the mapping of utilities using mixture models: An application to asthma

Objectives: To develop methods for mapping to preference-based measures using mixture model approaches. These methods are compared to map from the Asthma Quality of Life Questionnaire (AQLQ) to both EQ5D-5L and HUI-3 as the target health utility measures in an international dataset. Methods: Data from 856 patients with asthma collected as part of the Multi-Instrument Comparison (MIC) international project were used. Adjusted limited dependent variable mixture models (ALDVMMs) and beta-regression based mixture models were estimated. Optional inclusion of the gap between full health and the next value, and a mass point at the next feasible value were explored. Response-mapping could not be implemented due to missing data. Results: In all cases, model specifications which formally modelled the gap between full health and the next value were an improvement on those which did not. Mapping to HUI3 required more components in the mixture models than mapping to EQ5D-5L due to its uneven distribution. The optimal beta-based mixture models mapping to HUI3 included a probability mass at the utility value adjacent to full health. This is not the case when estimating EQ5D-5L, due to the low proportion of observations at this point. Conclusion: The beta-based mixture models marginally outperformed ALDVMM in this dataset when comparing models with the same number of components. This is at the expense of requiring a larger number of parameters and estimation time. Both model types are able to closely fit the data without biased characteristic of many mapping approaches. Skilled judgment is critical in determining the optimal model. Caution is required in ensuring a truly global maximum likelihood has been identified

The Effects of Breastfeeding on Childhood BMI: A Propensity Score Matching Approach

Background Many studies have found a statistical association between breastfeeding and childhood adiposity. This paper investigates whether breastfeeding has an effect on subsequent childhood body mass index (BMI) using propensity scores to account for confounding. Methods We use data from the Millennium Cohort Study, a nationally representative UK cohort survey, which contains detailed information on infant feeding and childhood BMI. Propensity score matching is used to investigate the mean BMI in children breastfed exclusively and partially for different durations of time. Results We find statistically significant influences of breastfeeding on childhood BMI, particularly in older children, when breastfeeding is prolonged and exclusive. At 7 years, children who were exclusively breastfed for 16 weeks had a BMI 0.28 kg/m 2 (95% confidence interval 0.07 to 0.49) lower than those who were never breastfed, a 2% reduction from the mean BMI of 16.6 kg/m 2 . Conclusions For this young cohort, even small effects of breastfeeding on BMI could be important. In order to reduce BMI, breastfeeding should be encouraged as part of wider lifestyle intervention. This evidence could help to inform public health bodies when creating public health guidelines and recommendations

The effects of breastfeeding on childhood BMI: a propensity score matching approach

This paper investigates the effect of breastfeeding on childhood body mass index (BMI). We use data from the Millennium Cohort Study (MCS), a nationally representative UK cohort survey, containing detailed infant feeding information, which allow us to explore the effects of a range of breastfeeding variables on the mean BMI of children breastfed for different durations and for exclusive and partial breastfeeding. Using propensity score matching, we find statistically significant influences of breastfeeding on childhood BMI, particularly in older children and when breastfeeding is prolonged and exclusive. The effects of breastfeeding on BMI are small in magnitude but large relative to the mean BMIs of children this age. At this young age, there is not a large difference in BMI between children who are identified as obese and those who are identified as normal weight, so even a small difference in BMI could mean the difference between children being overweight or a healthy weight. We suggest that breastfeeding should be encouraged as part of wider lifestyle interventions in order to help reduce BMI as well as improve other childhood outcomes. This could be important evidence for public health bodies when creating public health guidelines and recommendations

Family Lifestyle Dynamics and Childhood Obesity: Evidence from the Millennium Cohort Study

Using data from the Millennium Cohort Study, we investigate the dynamic relationship between underlying family lifestyle and childhood obesity during early childhood. We use a dynamic latent factor model, an approach that allows us to identify family lifestyle, its evolution over time and its influence on childhood obesity and other observable outcomes. We find that family lifestyle is persistent and has a significant influence on childhood weight status as well as other outcomes for all family members. Interventions should therefore be prolonged and persuasive and target the underlying lifestyle of a family as early as possible during childhood in order to have the greatest cumulative influence. Furthermore, the results indicate that to reduce inequalities in childhood obesity, policy makers should target disadvantaged families and design interventions specifically for these families

Field study of infiltration capacity reduction of porous mixture surfaces

Porous surfaces have been used all over the world in source control techniques to minimize flooding problems in car parks. Several studies highlighted the reduction in the infiltration capacity of porous mixture surfaces after several years of use. Therefore, it is necessary to design and develop a new methodology to quantify this reduction and to identify the hypothetical differences in permeability between zones within the same car park bay due to the influence of static loads in the parked vehicles. With this aim, nine different zones were selected in order to check this hypothesis (four points under the wheels of a standard vehicle and five points between wheels). This article presents the infiltration capacity reduction results, using the LCS permeameter, of Polymer-Modified Porous Concrete (9 bays) and Porous Asphalt (9 bays) surfaces in the University of Cantabria Campus parking area (Spain) 5 years after their construction. Statistical analysis methodology was proposed for assessing the results. Significant differences were observed in permeability and reduction in infiltration capacity in the case of porous concrete surfaces, while no differences were found for porous asphalt depending on the measurement zone

Mapping the FACT-B instrument to EQ-5D-3L in patients with breast cancer using adjusted limited dependent variable mixture models versus response mapping

Objectives Preference based measures (PBMs) of health, such as EQ-5D-3L, are required to calculate QALYs for use in cost-effectiveness analysis, but are often not recorded in clinical studies. In these cases, mapping can be used to estimate PBMs. We model the relationship between EQ-5D-3L and Functional Assessment of Cancer Therapy - Breast Cancer (FACT-B), comparing indirect and direct mapping methods, and the use of FACT-B summary score verses subscale scores. Methods We use data from 3 clinical studies for advanced breast cancer providing 11,958 observations with full information on FACT-B and EQ-5D-3L. We compare direct mapping using adjusted limited dependent variable mixture models (ALDVMMs) with indirect mapping using seemingly unrelated ordered probit models. EQ-5D-3L was estimated as a function of FACT-B and other patient related covariates. Results The use of FACT-B subscales was better than using total FACT-B score. A good fit to the observed data was observed across the range of disease severity in all models. ALDVMMs outperform the indirect mapping. The breast cancer specific scale significantly predicts EQ-5D-3L and this subscale has large influences on pain and self-care dimensions of EQ-5D-3L. Conclusion This paper adds to the growing literature that demonstrates the performance of the ALDVMM method for mapping. Regardless of which model is used, the subscales of FACT-B should be included as independent variables wherever possible. The breast cancer specific subscales of FACT-B are important in predicting EQ-5D-3L. This suggests that generic cancer measures should not be used for utility mapping in patients with breast cancer

Water quality and quantity assessment of pervious pavements performance in experimental car park areas

Pervious pavements have become one of the most used sustainable urban drainage system (SUDS) techniques in car parks. This research paper presents the results of monitoring water quality from several experimental car park areas designed and constructed in Spain with bays made of interlocking concrete block pavement, porous asphalt, polymer-modified porous concrete and reinforced grass with plastic and concrete cells. Moreover, two different sub-base materials were used (limestone aggregates and basic oxygen furnace slag). This study therefore encompasses the majority of the materials used as permeable surfaces and sub-base layers all over the world. Effluent from the test bays was monitored for dissolved oxygen, pH, electric conductivity, total suspended solids, turbidity and total petroleum hydrocarbons in order to analyze the behaviour shown by each combination of surface and sub-base materials. In addition, permeability tests were undertaken in all car parks using the ‘Laboratorio Caminos Santander’ permeameter and the Cantabrian Portable Infiltrometer. All results are presented together with the influence of surface and sub-base materials on water quality indicators using bivariate correlation statistical analysis at a confidence level of 95%. The polymer-modified porous concrete surface course in combination with limestone aggregate sub-base presented the best performance

An evaluation of enhanced geotextile layer in permeable pavement to improve stormwater infiltration and attenuation

This paper reports on an evaluation of the properties of a novel structure known as OASIS® which was designed at Coventry University as an enhancement of the commercially available geotextiles when incorporated in the permeable pavement system (PPS). The impact on the hydraulic behaviour of a PPS was analysed through the study of infiltration rate, throughout the PPS and time required to reach the steady-state stage behaviour of the water within the PPS, under extreme rainfall intensities of 100 mm/hr, 200 mm/hr and 400 mm/hr, corresponding to a 100-year return period rainfall over a duration of 15 min in different parts of the world. The result indicated that the novel structure provides an extra benefit when incorporated in PPSs, delaying peak flow of a rainfall event by retaining and storing great volumes of water within its structure. These additional benefits are especially important under extreme rainfall events

A Survey of High-Quality Computational Libraries and their Impactin Science and Engineering Applications

Recently, a number of important scientific and engineering problems have been successfully studied and solved by means of computational modeling and simulation. Many of these computational models and simulations benefited from the use of available software tools and libraries to achieve high performance and portability. In this article, we present a reference matrix of the performance of robust, reliable and widely used tools mapped to scientific and engineering applications that use them. We aim at regularly maintaining and disseminating this matrix to the computational science community. This matrix will contain information on state-of-the-art computational tools, their applications and their use