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- Yoneyama, Sachiko, et al.
(författare)
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Gene-centric meta-analyses for central adiposity traits in up to 57 412 individuals of European descent confirm known loci and reveal several novel associations
- 2014
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 23:9, s. 2498-2510
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Tidskriftsartikel (refereegranskat)abstract
- Waist circumference (WC) and waist-to-hip ratio (WHR) are surrogate measures of central adiposity that are associated with adverse cardiovascular events, type 2 diabetes and cancer independent of body mass index (BMI). WC and WHR are highly heritable with multiple susceptibility loci identified to date. We assessed the association between SNPs and BMI-adjusted WC and WHR and unadjusted WC in up to 57 412 individuals of European descent from 22 cohorts collaborating with the NHLBIs Candidate Gene Association Resource (CARe) project. The study population consisted of women and men aged 2080 years. Study participants were genotyped using the ITMAT/Broad/CARE array, which includes 50 000 cosmopolitan tagged SNPs across 2100 cardiovascular-related genes. Each trait was modeled as a function of age, study site and principal components to control for population stratification, and we conducted a fixed-effects meta-analysis. No new loci for WC were observed. For WHR analyses, three novel loci were significantly associated (P 2.4 10(6)). Previously unreported rs2811337-G near TMCC1 was associated with increased WHR ( SE, 0.048 0.008, P 7.7 10(9)) as was rs7302703-G in HOXC10 ( 0.044 0.008, P 2.9 10(7)) and rs936108-C in PEMT ( 0.035 0.007, P 1.9 10(6)). Sex-stratified analyses revealed two additional novel signals among females only, rs12076073-A in SHC1 ( 0.10 0.02, P 1.9 10(6)) and rs1037575-A in ATBDB4 ( 0.046 0.01, P 2.2 10(6)), supporting an already established sexual dimorphism of central adiposity-related genetic variants. Functional analysis using ENCODE and eQTL databases revealed that several of these loci are in regulatory regions or regions with differential expression in adipose tissue.
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| 2. |
- Lindberg, Gunnar, et al.
(författare)
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Payer selon sa vitesse : Deux expériences de terrain destinées à limiter le risque de sélection adverse et le risque moral dans le secteur de l'assurance automobile
- 2010
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Ingår i: Les Cahiers Scientifiques du Transport. - Lyon : l'Association Francaise des Instituts de Transport et de Logistique. - 1150-8809. ; :57, s. 117-139
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Tidskriftsartikel (refereegranskat)abstract
- Around one million people are killed world wide every year in road-traffic accidents. The risks and consequences of accidents increase progressively with speed, which ultimately is determined by the individual driver. The behaviour of the motorist thus affects both her own and other peoples’ safety. Internalisation of external costs of road transport has hitherto been focused on distance-based taxes or insurance premiums. While these means may affect driven distance, they have no influence on driving behaviour. This paper argues that by linking on-board positioning systems to insurance premiums it is possible to reward careful driving and get drivers to self select into different risk categories depending on their compliance to speed limits. We report two economic field experiments that have tested ways to induce car-owners to have technical platforms installed in their vehicle in order to affect the extent of speeding. It is demonstrated that a bonus to remunerate those that have the device installed, tantamount to a lower insurance premium, increases drivers’ propensity to accept the technical devices. In a second experiment the size of the bonus is made dependent on the actual frequency of speeding. We find that this is a second way to discipline users to drive at legal speeds.
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| 4. |
- Thomas, Fridtjof, 1966-
(författare)
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A Bayesian approach to retrospective detection of change-points in road surface measurements
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- First-order autoregressive processes are analysed for sudden changes in parameter value. In its most general form, a multivariate vector of measurements is allowed, and no prior knowledge about the involved parameters is required. Furthermore, no distributional assumptions about the nature of the sudden change are made, and arbitrary prior distributions over the space of all possible change-points are allowed. The change may be in level, variance, or autocorrelation, or in some combinations of these.Posterior probability distributions are derived for the location of a change-point conditional on the existence of such a change-point somewhere. The question whether or not there is a change present somewhere in the series is addressed in terms of posterior odds.The for the posterior odds needed Bayes factors are only defined up to an arbitrary constant due to the use of improper prior distributions on most of the model parameters. This indeterminacy is resolved by the use of minimal imaginary training samples.The emphasis is on analytical solutions based on an approximate version of the likelihood in order to allow for fast algorithms. Nevertheless, details for a Gibbs sampler are given based on the exact model, assuming that the unobserved initial conditions come from the stationary distributions of the involved processes. This sampler employs conditional conjugacy when possible. However, the full conditionals of the autoregressive coefficients are not of standard form and a slice sampler is implemented.The motivating application is in the field of road maintenance, where pavement surfaces are frequently measured and the need arises to partition roads into parts, which can be considered homogeneous with respect to the measured characteristics. In Sweden, the international roughness index (IRI - a measure of a road's longitudinal unevenness) and rutting are the two measurements of foremost interest. The use of the developed theory is exemplified throughout by these measurement series, which are collected by so-called Laser-RST-vehicles. A well-motivated segmentation of a road is a prerequisite for a successful handling of the road sections in a pavement management system, which ultimately aims at efficiently providing road infrastructure of high quality.In order to make this work accessible to others than professional statisticians, the basic concepts involved in the analysis are described in the introductory section.
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| 7. |
- Thomas, Fridtjof
(författare)
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Assessing heavy-vehicle accident rates for marginal cost calculations : Outline of a full probability modelling approach
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The problem of determining marginal costs associated to heavy vehicles'involvement in traffic accidents can be factored into two sub-problems: oneof determining the rate with which various trucks are involved in accidentsand one of evaluating the with an accident associated consequences. We focushere entirely on the first aspect, and suggest a full probability modellingapproach in order to estimate the accident rates of various types of trucks.This approach allows us to jointly account for information obtained from theSwedish police-reported accident register, the Swedish vehicle register, theregister of the annually roadworthiness inspection, and the sample survey'Transports by Swedish Trucks in Sweden'. This survey contains importantinformation about the exposure of various types of vehicles.
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| 8. |
- Thomas, Fridtjof
(författare)
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Att systematisera objektspecifik osäkerhet i EVA-kalkyler : diskussion och exempel
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Swedish Road Administration (SRA) performs cost-benefit studies for road infrastructure projects utilizing a specialized computer program known by its Swedish acronym EVA. This report describes three possible approaches to accomplish sensitivity studies of the SRA's costbenefit studies. A simple example explains how these approaches are applied in the context of the SRA's cost-benefit studies. First, the popular one-factor-at-a-time method is described. The major drawback of this approach is that interaction of factors cannot be addressed. The method of Monte Carlo simulation allows for this possibility. This method uses brute force computational power to calculate a large number of outcomes based on randomly altered values for the included factors. However, Monte Carlo simulation necessitates the assessment of the multivariate stochastic distribution of considered factors. It is generally very difficult to assess multivariate distributions and it is consequently difficult to utilize the full potential of the Monte Carlo technique. We suggest therefore that the SRA's sensitivity studies are based on few simulation runs where the factors are altered simultaneously in each run. The number of runs is kept low by appropriate selection of factor combinations in each run, utilizing statistical design theory for experiments. The so obtained "observations" are used to estimate a response surface, which is essentially a simplified regression relationship between the factors that matter in the context and the resulting ratio between a project's net present value and its cost. This method handles possible interaction between factors, requires from the investigator merely the determination of reasonable upper and lower bounds for included factors, and does not require a large number of simulation runs.
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