A.L.M. Dekkers - Academia.edu (original) (raw)

Papers by A.L.M. Dekkers

European Journal of Nutrition, 2017

range 86.6-99.3%), and a higher intake for saturated fat [88.1% (95% CI 84.1-98.9)]. Furthermore,... more range 86.6-99.3%), and a higher intake for saturated fat [88.1% (95% CI 84.1-98.9)]. Furthermore, mean intakes of energy, fiber, fruit, and vegetables were significantly lower in Dutch food bank recipients than in the DNFCS-all and the DNFCS-low-SES [e.g., daily mean fruit intake (g) food bank recipients 62.8 (95% CI 45.5-76.5), DNFCS-all 105.8 (95% CI 105.4-117.9), and DNFCS-low-SES 85.1 (95% CI 78.7-100.2)]. Fish intake was significantly lower compared with the DNFCS-all, but not compared with the DNFCS-low-SES. Conclusions Dutch food bank recipients, who largely rely on the content of food parcels, are not able to meet the nutritional guidelines for a healthy diet, and their dietary intake is poorer than the general as well as the low-SES sample of the Dutch adult population. More research is needed on how to improve the dietary intake of this vulnerable population subgroup, by, e.g., revising the content of the food parcels, and to develop effective intervention activities.

EFSA Supporting Publications, 2012

The present document has been produced and adopted by the bodies identified above as author(s). I... more The present document has been produced and adopted by the bodies identified above as author(s). In accordance with Article 36 of Regulation (EC) No 178/2002, this task has been carried out exclusively by the author(s) in the context of a grant agreement between the European Food Safety Authority and the author(s). The present document is published complying with the transparency principle to which the Authority is subject. It cannot be considered as an output adopted by the Authority. The European Food Safety Authority reserves its rights, view and position as regards the issues addressed and the conclusions reached in the present document, without prejudice to the rights of the authors.

Studies in Environmental Science

... modelling. JMM Aben a , PSC Heuberger b , RC Acharya b and ALM Dekkers b. a Air Quality Resea... more ... modelling. JMM Aben a , PSC Heuberger b , RC Acharya b and ALM Dekkers b. a Air Quality Research Laboratory, National Institute of Public Health and Environmental Protection, Postbox 1, 3720 BA Bilthoven, Netherlands. ...

Studies in Environmental Science, 1995

Environmental information on cause-effect chains is obtained by combining results of measurements... more Environmental information on cause-effect chains is obtained by combining results of measurements and survey data with statistical and process oriented models. For proper use of the information it is important to have a good understanding of its reliability. This paper addresses the problem of assessing the reliability of information obtained from different models and measurements. A reliability factor is introduced

Siam Journal on Applied Mathematics - SIAMAM, 1987

An easy proof is given for the weak consistency of Pickands' estimate of the main parameter of an... more An easy proof is given for the weak consistency of Pickands' estimate of the main parameter of an extreme-value distribution. Moreover further natural conditions are given for strong consistency and for asymptotic normality of the estimate.

Journal of Nutrition, 2011

Statistical modeling of habitual micronutrient intake from food and dietary supplements using sho... more Statistical modeling of habitual micronutrient intake from food and dietary supplements using short-term measurements is hampered by heterogeneous variances and multimodality. Summing short-term intakes from food and dietary supplements prior to simple correction for within-person variation (first add then shrink) may produce estimates of habitual total micronutrient intake so badly biased as to be smaller than estimates of habitual intake from food sources only. A 3-part model using a first shrink then add approach is proposed to estimate the habitual micronutrient intake from food among nonsupplement users, food among supplement users, and supplements. The population distribution of habitual total micronutrient intake is estimated by combining these 3 habitual intake distributions, accounting for possible interdependence between Eq. 2 and 3. The new model is an extension of a model developed by the USA National Cancer Institute. Habitual total vitamin D intake among young children was estimated using the proposed model and data from the Dutch food consumption survey (n = 1279). The model always produced habitual total intakes similar to or higher than habitual intakes from food sources only and also preserved the multimodal shape of the observed total vitamin D intake distribution. This proposed method incorporates several sources of covariate information that should provide more precise estimates of the habitual total intake distribution and the proportion of the population with intakes below/above cutpoint values. The proposed methodology could be useful for other complex situations, e.g. where high concentrations of micronutrients appear in episodically consumed foods.

British Journal of Nutrition, 2011

Studies using 24 h urine collections need to incorporate ways to validate the completeness of the... more Studies using 24 h urine collections need to incorporate ways to validate the completeness of the urine samples. Models to predict urinary creatinine excretion (UCE) have been developed for this purpose; however, information on their usefulness to identify incomplete urine collections is limited. We aimed to develop a model for predicting UCE and to assess the performance of a creatinine index usingpara-aminobenzoic acid (PABA) as a reference. Data were taken from the European Food Consumption Validation study comprising two non-consecutive 24 h urine collections from 600 subjects in five European countries. Data from one collection were used to build a multiple linear regression model to predict UCE, and data from the other collection were used for performance testing of a creatinine index-based strategy to identify incomplete collections. Multiple linear regression (n458) of UCE showed a significant positive association for body weight (β = 0·07), the interaction term sex × weight...

Stochastic Environmental Research and Risk Assessment, 2005

This paper discusses two model-based geostatistical methods for spatial interpolation of the numb... more This paper discusses two model-based geostatistical methods for spatial interpolation of the number of days that ground level ozone exceeds a threshold level. The first method assumes counts to approximately follow a Poisson distribution, while the second method assumes a log-Normal distribution. First, these methods were compared using an extensive data set covering the Netherlands, Belgium and Germany. Second, the focus was placed on only the Netherlands, where only a small data set was used. Bayesian techniques were used for parameter estimation and interpolation. Parameter estimates are comparable due to the log-link in both models. Incorporating data from adjacent countries improves parameter estimation. The Poisson model predicts more accurately (maximum kriging standard deviation of 2.16 compared to 2.69) but shows smoother surfaces than the log-Normal model. The log-Normal approach ensures a better representation of the observations and gives more realistic patterns (an RMSE of 2.26 compared to 2.44). Model-based geostatistical procedures are useful to interpolate limited data sets of counts of ozone exceedance days. Spatial risk estimates using existing prior information can be made relating health effects to environmental thresholds.

Stochastic Environmental Research and Risk Assessment, 2006

This paper illustrates the use of statistical techniques to standardize ground based measurements... more This paper illustrates the use of statistical techniques to standardize ground based measurements of particulate matter (PM10). Concentrations are interpolated over Western Europe using uncertain secondary information from a chemical transport model and of aerosol optical thickness from MODIS satellite observations. A consistent overview of PM10 concentrations over Europe based solely on ground based measurements is complicated by differences between countries. Different monitoring methods are used and calibrations are applied. There also is an inherent limitation to the spatial representativeness of ground based measurements. Validation showed that adding secondary information from either the chemical transport model or the satellite observations improved the PM10 mapping. The URMSE decreased from 5.14 to 4.26 and 4.58, respectively. A combination of both sources of secondary information gave the most accurate and precise predictions , with an URMSE of 3.62. This means that both external sources contain additional information on the spatial distribution of PM10 concentrations and should therefore be preferred.

Journal of Multivariate Analysis, 1993

The Centre for Mathematics and Computer Science is a research institute of the Stichting Mathemat... more The Centre for Mathematics and Computer Science is a research institute of the Stichting Mathematisch Centrum, which was founded on February 11, 1946, as a nonprofit institution aiming at the promotion of mathematics, computer science, and their applications. It is sponsored by the Dutch Government through the Netherlands Organization for the Advancement of Research (N.W.O.).

Journal of Environment Quality, 2002

Global Biogeochemical Cycles, 2005

Global Biogeochemical Cycles, 2009

We present a multiple linear regression model developed for describing global river export of dis... more We present a multiple linear regression model developed for describing global river export of dissolved SiO 2 (DSi) to coastal zones. The model, with river basin spatial scale and an annual temporal scale, is based on four variables with a significant influence on DSi yields (soil bulk density, precipitation, slope, and area with volcanic lithology) for the predam situation. Cross validation showed that the model is robust with respect to the selected model variables and coefficients. The calculated global river export of DSi is 380 Tg a À1 (340-427 Tg a À1). Most of the DSi is exported by global rivers to the coastal zone of the Atlantic Ocean (41%), Pacific Ocean (36%), and Indian Ocean (14%). South America and Asia are the largest contributors (25% and 23%, respectively). DSi retention in reservoirs in global river basins may amount to 18-19%.

Food and Chemical Toxicology, 2012

In dietary exposure assessment, statistical methods exist for estimating the usual intake distrib... more In dietary exposure assessment, statistical methods exist for estimating the usual intake distribution from daily intake data. These methods transform the dietary intake data to normal observations, eliminate the within-person variance, and then back-transform the data to the original scale. We propose Gaussian Quadrature (GQ), a numerical integration method, as an efficient way of back-transformation. We compare GQ with six published methods. One method uses a log-transformation, while the other methods, including GQ, use a Box-Cox transformation. This study shows that, for various parameter choices, the methods with a Box-Cox transformation estimate the theoretical usual intake distributions quite well, although one method, a Taylor approximation, is less accurate. Two applications--on folate intake and fruit consumption--confirmed these results. In one extreme case, some methods, including GQ, could not be applied for low percentiles. We solved this problem by modifying GQ. One method is based on the assumption that the daily intakes are log-normally distributed. Even if this condition is not fulfilled, the log-transformation performs well as long as the within-individual variance is small compared to the mean. We conclude that the modified GQ is an efficient, fast and accurate method for estimating the usual intake distribution.

Epidemiology and Infection, 2009

SUMMARYTo gain insight into pertussis disease dynamics, we studied age-specific long-term periodi... more SUMMARYTo gain insight into pertussis disease dynamics, we studied age-specific long-term periodicity and seasonality of pertussis in The Netherlands. Hierarchical time-series models were used to analyse the monthly reported pertussis incidence in January 1996–June 2006 by age group. The incidence of pertussis showed a slightly increasing long-term trend with highest incidence rates seen in 1996, 1999, 2001 and 2004. For all age groups the annual peak incidence was found in August, except for the 13–18 years age group where the peak occurred in November. Monthly trends in adults showed high correlation with trends in age groups 0–4 years (0·94) and 5–12 years (0·92). We found no evidence for a relationship between annual rises in pertussis and the opening of schools. Concurrent annual fluctuations of pertussis incidence in adults and infants suggest frequent transmission within and between these age groups. Studying trends offers insight into transmission dynamics and may facilitate...

To obtain a spatial distribution of the ammonia concentrations in the Netherlands measurements of... more To obtain a spatial distribution of the ammonia concentrations in the Netherlands measurements of ammonia have been performed on a grid of 15 x 15 km (159 locations) with passive samplers from September 2000 until September 2001. The highest ammonia concentrations represented by the grid are observed in all months in the East of Noord-Brabant and the North of Limburg with yearly average concentrations of 15 ug/m3. Elevated concentrations of about 10 ug/m3 are seen in the Gelderse Vallei, the Achterhoek and Twente and concentrations of about 7 ug/m3 are seen in central Overijssel and Friesland. De monthly ammonia concentrations averaged over the Netherlands varied from 4 ug/m3 in fall of 2000 to 9.6 ug/m3 in May 2001 with a yearly average of 6.6 ug/m3. The yearly average concentration calculated from the 159 measurement locations yields also 6.6 ug/m3, while the average on the eight LML-locations is higher with 7.8 ug/m3.

The Annals of Statistics, 1989