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- Adalbjornsson, S. I., et al.
(author)
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Estimating Periodicities in Symbolic Sequences Using Sparse Modeling
- 2015
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In: Ieee Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 63:8, s. 2142-2150
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Journal article (peer-reviewed)abstract
- In this paper, we propose a method for estimating statistical periodicities in symbolic sequences. Different from other common approaches used for the estimation of periodicities of sequences of arbitrary, finite, symbol sets, that often map the symbolic sequence to a numerical representation, we here exploit a likelihood-based formulation in a sparse modeling framework to represent the periodic behavior of the sequence. The resulting criterion includes a restriction on the cardinality of the solution; two approximate solutions are suggested-one greedy and one using an iterative convex relaxation strategy to ease the cardinality restriction. The performance of the proposed methods are illustrated using both simulated and real DNA data, showing a notable performance gain as compared to other common estimators.
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- Blom, Victoria, et al.
(author)
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Self-Reported General Health, Overall and Work-Related Stress, Loneliness, and Sleeping Problems in 335,625 Swedish Adults from 2000 to 2016.
- 2020
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In: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 17:2
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Journal article (peer-reviewed)abstract
- The prevalence of poor health, in particular stress-related mental ill-health, is increasing over time and birth cohorts. As rapid societal changes have occurred in the last decade and still are occurring, there is an interest in investigating the trends in health-related factors. The aim of the present study was to investigate trends in self-reported general health, overall stress, work-related stress, feelings of loneliness, and sleeping problems in 335,625 Swedish adults across categories of gender, geographic regions, length of education, and age from 2000 to 2016. On population level, sleeping problems and poor general health have increased markedly and significantly, while experiences of work stress decreased between 2000 and 2016 (p < 0.05). Overall stress and level of loneliness were unchanged (p > 0.05). The risk of having ≥3 symptoms (any of poor or very poor general health, often or very often perceived overall stress, loneliness, or sleeping problems) has increased significantly from 2000 to 2016 (ß = 1034 (1027-1040)). This increase was significantly higher in young (ß = 1052 (1038-1065)) and individuals with lower education (ß = 1056 (1037-1076)) compared to older and high length of education.
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- Bolin, David, 1983, et al.
(author)
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Calibrating regionally downscaled precipitation over Norway through quantile-based approaches
- 2016
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In: Advances in Statistical Climatology, Meteorology and Oceanography. - 2364-3579 .- 2364-3587. ; 2, s. 39-47
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Journal article (peer-reviewed)abstract
- Dynamical downscaling of earth system models is intended to produce high-resolution climate in- formation at regional to local scales. Current models, while adequate for describing temperature distributions at relatively small scales, struggle when it comes to describing precipitation distributions. In order to better match the distribution of observed precipitation over Norway, we consider approaches to statistical adjustment of the output from a regional climate model when forced with ERA-40 reanalysis boundary conditions. As a second step, we try to correct downscalings of historical climate model runs using these transformations built from downscaled ERA-40 data. Unless such calibrations are successful, it is difficult to argue that scenario-based downscaled climate projections are realistic and useful for decision makers. We study both full quantile cali- brations and several different methods that correct individual quantiles separately using random field models. Results based on cross-validation show that while a full quantile calibration is not very effective in this case, one can correct individual quantiles satisfactorily if the spatial structure in the data are accounted for. Interestingly, different methods are favoured depending on whether ERA-40 data or historical climate model runs are adjusted.
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- Bolin, David, 1983, et al.
(author)
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Latent Gaussian random field mixture models
- 2019
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In: Computational Statistics & Data Analysis. - : Elsevier BV. - 0167-9473. ; 130, s. 80-93
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Journal article (peer-reviewed)abstract
- For many problems in geostatistics, land cover classification, and brain imaging the classical Gaussian process models are unsuitable due to sudden, discontinuous, changes in the data. To handle data of this type, we introduce a new model class that combines discrete Markov random fields (MRFs) with Gaussian Markov random fields. The model is defined as a mixture of several, possibly multivariate, Gaussian Markov random fields. For each spatial location, the discrete MRF determines which of the Gaussian fields in the mixture that is observed. This allows for the desired discontinuous changes of the latent processes, and also gives a probabilistic representation of where the changes occur spatially. By combining stochastic gradient minimization with sparse matrix techniques we obtain computationally efficient methods for both likelihood-based parameter estimation and spatial interpolation. The model is compared to Gaussian models and standard MRF models using simulated data and in application to upscaling of soil permeability data. (C) 2018 Elsevier B.V. All rights reserved.
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- Bolin, David, 1983, et al.
(author)
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Spatially adaptive covariance tapering
- 2016
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In: Spatial Statistics. - : Elsevier BV. - 2211-6753. ; 18, s. 163-178
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Journal article (peer-reviewed)abstract
- © 2016 Elsevier B.V.Covariance tapering is a popular approach for reducing the computational cost of spatial prediction and parameter estimation for Gaussian process models. However, tapering can have poor performance when the process is sampled at spatially irregular locations or when non-stationary covariance models are used. This work introduces an adaptive tapering method in order to improve the performance of tapering in these problematic cases. This is achieved by introducing a computationally convenient class of compactly supported non-stationary covariance functions, combined with a new method for choosing spatially varying taper ranges. Numerical experiments are used to show that the performance of both kriging prediction and parameter estimation can be improved by allowing for spatially varying taper ranges. However, although adaptive tapering outperforms regular tapering, simply dividing the data into blocks and ignoring the dependence between the blocks is often a better method for parameter estimation.
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- Ekblom Bak, Elin, 1981-, et al.
(author)
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Decline in cardiorespiratory fitness in the Swedish working force between 1995 and 2017.
- 2019
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In: Scandinavian Journal of Medicine and Science in Sports. - : John Wiley & Sons. - 0905-7188 .- 1600-0838. ; 29:2, s. 232-239
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Journal article (peer-reviewed)abstract
- BACKGROUND: Long-term trend analyses of cardiorespiratory fitness (VO2 max) in the general population are limited.OBJECTIVES: To describe trends in VO2 max from 1995 to 2017 in the Swedish working force and to study developments across categories of sex, age, education, and geographic regions.METHODS: 354.277 participants (44% women, 18-74 years) who participated in a nationwide occupational health service screening between 1995 and 2017 were included. Changes in standardized mean values of absolute (L·min-1 ) and relative (ml·min-1 ·kg-1 ) VO2 max, and the proportion with low (<32) relative VO2 max are reported. VO2 max was estimated using a submaximal cycle test.RESULTS: Absolute VO2 max decreased by -6.7% (-0.19 L·min-1 ) in the total population. Relative VO2 max decreased by -10.8% (-4.2 ml·min-1 ·kg-1 ) with approximately one-third explained by a simultaneous increase in body mass. Decreases in absolute fitness were more pronounced in men vs. women (8.7% vs. 5.3%), in younger vs. older (6.5% vs 2.3%), in short (11.4%) vs. long (4.5%) education, and in rural vs. urban regions (6.5% vs 3.5%), all p<0.001. The proportions with low VO2 max increased from 27% to 46% (p<0.001).CONCLUSION: Between 1995 and 2017, there was a steady and pronounced decline in mean cardiorespiratory fitness in Swedish adults. Male gender, young age, short education and living in a rural area were predictive of greater reductions. The proportion with low cardiorespiratory fitness almost doubled. Given the strong associations between cardiorespiratory fitness and multiple morbidities and mortality, preventing further decreases is a clear public health priority, especially for vulnerable groups. This article is protected by copyright. All rights reserved.
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- Hemmingsson, Erik, et al.
(author)
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Prevalence and time trends of overweight, obesity and severe obesity in 447,925 Swedish adults, 1995–2017
- 2021
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In: Scandinavian Journal of Public Health. - : Sage Publications. - 1403-4948 .- 1651-1905. ; 49:4, s. 377-383
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Journal article (peer-reviewed)abstract
- Aims: The purpose of this research was to describe the current prevalence and historic trends in overweight, obesity and severe obesity in Sweden. Methods: Data on BMI, age, gender, education and geographic region were obtained in n=447,925 Swedish adults through a nationwide screening test (1995?2017). To account for sampling variations, we quantified prevalence estimates and time trends using standardized values (direct method) to all 18?74-year-old Swedes, using nationwide databases. Rates of overweight (BMI ?25 kg/m2), obesity (BMI ?30 kg/m2) and severe obesity (BMI ?35 kg/m2) were calculated across gender, age, education and geographic categories. Years were grouped into two-year sampling periods (except the first period where we used three years) for increased power. We used multivariable logistic regression to quantify independent associations between age, gender, education and region with obesity development and current prevalence rates. Results: In 2016/17 the unstandardized prevalence of overweight, obesity and severe obesity were 55.1%, 16.6% and 4.2%, respectively. Factors associated with a higher obesity prevalence were male gender, older age, lower education and residing in a rural region (all P<0.001). Between 1995 and 2017 the prevalence of severe obesity increased by 153%, compared to obesity (+86%) and overweight (+23%). While there were similar increases in obesity across gender and age groups, people with low education (vs high) and rural areas (vs urban) had a higher prevalence increase (both P<0.001). Conclusions: Rates of overweight, obesity and severe obesity have increased markedly in Swedish adults since 1995. Priority groups for prevention efforts include individuals with low education and those living in rural areas.
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