Publications

By Year By Type

Articles

• Åkerblom, S., Larsson, J., Malmström, E.-M., Persson, E., & Westergren, H. (2019). Acceptance: A Factor to Consider in Persistent Pain after Neck Trauma. Scandinavian Journal of Pain, 19(4), 733–741. https://doi.org/10.1515/sjpain-2019-0021
  

  @article{akerblom2019,
    title = {Acceptance: A Factor to Consider in Persistent Pain after Neck Trauma},
    shorttitle = {Acceptance},
    author = {Åkerblom, Sophia and Larsson, Johan and Malmström, Eva-Maj and Persson, Elisabeth and Westergren, Hans},
    date = {2019},
    journaltitle = {Scandinavian Journal of Pain},
    volume = {19},
    pages = {733--741},
    issn = {1877-8879},
    doi = {10.1515/sjpain-2019-0021},
    url = {https://www.degruyter.com/view/j/sjpain.2019.19.issue-4/sjpain-2019-0021/sjpain-2019-0021.xml},
    urldate = {2020-01-14},
    number = {4}
  }
  
• Larsson, J., Ekvall Hansson, E., & Miller, M. (2015). Increased Double Support Variability in Elderly Female Fallers with Vestibular Asymmetry. Gait & Posture, 41(3), 820–824. https://doi.org/10.1016/j.gaitpost.2015.02.019
  

  @article{larsson2015,
    title = {Increased Double Support Variability in Elderly Female Fallers with Vestibular Asymmetry},
    author = {Larsson, Johan and Ekvall Hansson, Eva and Miller, Michael},
    date = {2015-03},
    journaltitle = {Gait \& Posture},
    shortjournal = {Gait Posture},
    volume = {41},
    pages = {820--824},
    issn = {1879-2219},
    doi = {10.1016/j.gaitpost.2015.02.019},
    eprint = {25800649},
    eprinttype = {pmid},
    langid = {english},
    number = {3}
  }
  

  There is a broad consensus on the coupling of deteriorating gait and vestibular asymmetry, which has proved predictive of falls in the elderly. To date, research on this coupling remains inconclusive and has not focused specifically on fallers. In the present study, differences in gait variability were examined in a population of elderly females with fall-related wrist fractures, divided into samples with positive (N=28, 73±9 years) and negative head-shaking tests (N=6, 67±9 years). Swing, stance, and double support time variability were measured in preferred speed walking using GAITRite(®) and statistically evaluated in multivariate analysis of covariance with age as covariate. Results showed overall greater gait variability for the positive nystagmus group (p=0.03) despite non-significant adjustment of the covariate (p=0.18). In post-hoc analysis, the effect on variability in double support time emerged as a significant and large contributor to this difference (p=0.009, ηp(2)=0.20). Conversely, the ability of swing and stance time variability to discriminate between groups was both non-significant and small (p=0.25, ηp(2)=0.04 and p=0.34, ηp(2)=0.03 respectively). We believe that the increased variability might stem from a strategic use of double support to re-stabilize from balance perturbations during gait. To some extent, these results diverge from previous findings and need to be reassessed in future studies.
• Larsson, J. (2016). A Letter to the Editor Regarding “Serratus Anterior or Pectoralis Minor: Which Muscle Has the Upperhand during Protraction Exercises?” Manual Therapy, 24, e1. https://doi.org/10/gcsk6d
  

  @article{larsson2016a,
    title = {A Letter to the Editor Regarding “{{Serratus}} Anterior or Pectoralis Minor: Which Muscle Has the Upperhand during Protraction Exercises?”},
    shorttitle = {A Letter to the Editor Regarding “{{Serratus}} Anterior or Pectoralis Minor},
    author = {Larsson, Johan},
    date = {2016-08-01},
    journaltitle = {Manual Therapy},
    shortjournal = {Manual Therapy},
    volume = {24},
    pages = {e1},
    issn = {1356-689X, 1532-2769},
    doi = {10/gcsk6d},
    url = {/article/S1356-689X(16)30004-2/abstract},
    urldate = {2016-09-28},
    eprint = {27133020, 27133020},
    eprinttype = {pmid},
    langid = {english}
  }
  
• Larsson, J., Miller, M., & Ekvall Hansson, E. (2016). Vestibular Asymmetry Increases Double Support Time Variability in a Counter-Balanced Study on Elderly Fallers. Gait & Posture, 45, 31–34. https://doi.org/10.1016/j.gaitpost.2015.12.023
  

  @article{larsson2016c,
    title = {Vestibular Asymmetry Increases Double Support Time Variability in a Counter-Balanced Study on Elderly Fallers},
    author = {Larsson, Johan and Miller, Michael and Ekvall Hansson, Eva},
    date = {2016-03},
    journaltitle = {Gait \& Posture},
    shortjournal = {Gait \& Posture},
    volume = {45},
    pages = {31--34},
    issn = {0966-6362},
    doi = {10.1016/j.gaitpost.2015.12.023},
    url = {http://www.sciencedirect.com/science/article/pii/S0966636215009911},
    urldate = {2016-04-11}
  }
  

  Vestibular asymmetry is a common cause of dizziness in the elderly, for whom it precipitates the risk of falling. Previous studies have shown that those with vestibular asymmetry displayed an altered variability in double support time (DST) compared to controls. However, swing time (SwT) variability findings are conflicting. In this study, we investigated if vestibular asymmetry might be causally connected to increased DST variability. We studied a group of eight elderly fallers with wrist fractures across three months, during which time four of them regained vestibular symmetry while four others developed an asymmetry. We evaluated the variability of DST and SwT, both when the participants suffered from vestibular asymmetry and when they did not. On average, variability in DST was significantly greater by 2.38 %CV (coefficient of variation) when participants scored positive for vestibular asymmetry compared to when not, t(5) = 4.39, p = 0.01, ξ = 1.67. In contrast, SwT variability differed non-significantly by 0.44 %CV when participants had tested positive versus negative for vestibular asymmetry, t(5) = −0.87, p = 0.39, ξ = −0.29. As a possible rationale for our results, we propose that increased DST variability may be the result of a re-stabilization strategy. Further research on DST variability and its correlation to the duration of vestibular asymmetry is recommended.
• Larsson, J. (2018). Mapping Physical Therapy Research: The Geographical Affiliations and Methodological Quality of 2,959 Randomized Controlled Trials. Physiotherapy Theory and Practice, 34(9), 723–729. https://doi.org/10.1080/09593985.2018.1423657
  

  @article{larsson2018b,
    title = {Mapping Physical Therapy Research: The Geographical Affiliations and Methodological Quality of 2,959 Randomized Controlled Trials},
    shorttitle = {Mapping Physical Therapy Research},
    author = {Larsson, Johan},
    date = {2018-01-08},
    journaltitle = {Physiotherapy Theory and Practice},
    volume = {34},
    pages = {723--729},
    issn = {1532-5040},
    doi = {10.1080/09593985.2018.1423657},
    number = {9}
  }
  

  Evidence suggests that research benefits from diversity, yet science is concentrated to a small group of countries. Diversity in physical therapy research has so far not been studied thorough-ly and this is the first study to map physical therapy research geographically. The objective was to study the frequency and methodological quality of physical therapy-related randomized controlled trials (RCTs) across the world. PEDro was searched for RCTs in physical therapy published between January 1 2015 and December 5 2016. For each trial, the first and last authors’ affiliations and the PEDro scale were extracted. Using the first and last authors’ affiliations, each article was geocoded using the Data Science Toolkit API. The search located 2,959 RCTs, which were affiliated primarily with a small cluster of countries. The median PEDro score for all trials was 5 (IQR 4:7). The geographical spread of the RCTs was focused around Europe, the Middle East, Southeast Asia, Oceania, the United States, and parts of South America. The lack of diversity might be problematic for the research field, even though the average clinical trial in physical therapy is of fair quality.
• Westergren, H., Larsson, J., Freeman, M., Carlsson, A., Jöud, A., & Malmström, E.-M. (2017). Sex-Based Differences in Pain Distribution in a Cohort of Patients with Persistent Post-Traumatic Neck Pain. Disability and Rehabilitation, 40(9), 1085–1091. https://doi.org/10.1080/09638288.2017.1280543
  

  @article{westergren2017,
    title = {Sex-Based Differences in Pain Distribution in a Cohort of Patients with Persistent Post-Traumatic Neck Pain},
    author = {Westergren, Hans and Larsson, Johan and Freeman, Michael and Carlsson, Anna and Jöud, Anna and Malmström, Eva-Maj},
    date = {2017-01-27},
    journaltitle = {Disability and Rehabilitation},
    volume = {40},
    pages = {1085--1091},
    doi = {10.1080/09638288.2017.1280543},
    url = {http://www.tandfonline.com/eprint/RK8tusJswJCsa9YakGDW/full},
    urldate = {2017-01-28},
    langid = {english},
    number = {9}
  }
  

  Objectives: To analyze a cohort of 745 consecutive patients referred to a regional specialist clinic for evaluation of post-traumatic neck pain during a five-year period. Methods: A cross-sectional observational study of baseline assessments performed by multi-professional rehabilitation teams according to a standardized checklist. Results: The cohort contained nearly twice as many females as males (64% versus 36%). The type of injury did not differ between sexes. Of the entire cohort, 38% were diagnosed with widespread pain, 50% with regional pain, and 12% with local pain. The pain distribution among the females was 43% widespread, 48% regional, and 9% local, and corresponding figures among males were 29%, 53%, and 18%. Longer time between trauma and assessment did not affect pain distribution among the men, but a tendency towards more widespread pain was observed among the women. Discussion: The importance of "female sex" as risk factor for the development of persistent pain after neck trauma needs to be discussed further. The high frequency of regional and widespread pain among patients with persistent neck pain after trauma calls for both multidisciplinary assessments and treatment strategies. The relationships between different pain distribution patterns, disability, activity, and psychological factors need to be studied further.

Proceedings

• Larsson, J., & Gustafsson, P. (2018). A Case Study in Fitting Area-Proportional Euler Diagrams with Ellipses Using Eulerr. Proceedings of International Workshop on Set Visualization and Reasoning, 2116, 84–91. http://ceur-ws.org/Vol-2116/paper7.pdf
  

  @inproceedings{larsson2018,
    title = {A Case Study in Fitting Area-Proportional {{Euler}} Diagrams with Ellipses Using Eulerr},
    booktitle = {Proceedings of {{International Workshop}} on {{Set Visualization}} and {{Reasoning}}},
    author = {Larsson, Johan and Gustafsson, Peter},
    date = {2018-06-18},
    volume = {2116},
    pages = {84--91},
    publisher = {{CEUR Workshop Proceedings}},
    location = {{Edinburgh, United Kingdom}},
    url = {http://ceur-ws.org/Vol-2116/paper7.pdf},
    eventtitle = {Set {{Visualization}} and {{Reasoning}} 2018}
  }
  
• Larsson, J., Bogdan, M., & Wallin, J. (6-12 Dec 2020 (forthcoming)6-12 Dec 2020 (forthcoming). The Strong Screening Rule for SLOPE. Advances in Neural Information Processing Systems 33.
  

  @inproceedings{larsson2020c,
    title = {The Strong Screening Rule for {{SLOPE}}},
    booktitle = {Advances in {{Neural Information Processing Systems}} 33},
    author = {Larsson, Johan and Bogdan, Małgorzata and Wallin, Jonas},
    year = {6-12 Dec 2020 (forthcoming)},
    publisher = {{Curran Associates, Inc.}},
    location = {{Virtual}},
    eventtitle = {Neural {{Information Procession Systems}} 2020}
  }
  

  Extracting relevant features from data sets where the number of observations n is much smaller then the number of predictors p is a major challenge in modern statistics. Sorted L-One Penalized Estimation (SLOPE)—a generalization of the lasso—is a promising method within this setting. Current numerical procedures for SLOPE, however, lack the efficiency that respective tools for the lasso enjoy, particularly in the context of estimating a complete regularization path. A key component in the efficiency of the lasso is predictor screening rules: rules that allow predictors to be discarded before estimating the model. This is the first paper to establish such a rule for SLOPE. We develop a screening rule for SLOPE by examining its subdifferential and show that this rule is a generalization of the strong rule for the lasso. Our rule is heuristic, which means that it may discard predictors erroneously. In our paper, however, we show that such situations are rare and easily safeguarded against by a simple check of the optimality conditions. Our numerical experiments show that the rule performs well in practice, leading to improvements by orders of magnitude for data in the p >> n domain, as well as incurring no additional computational overhead when n > p.
• Larsson, J., Bogdan, M., & Wallin, J. (2020). The Strong Screening Rule for SLOPE. In H. Larochelle, M. Ranzato, R. Hadsell, M. F. Balcan, & H. Lin (Eds.), Advances in Neural Information Processing Systems 33 (Vol. 33, pp. 14592–14603). Curran Associates, Inc. https://proceedings.neurips.cc/paper/2020/file/a7d8ae4569120b5bec12e7b6e9648b86-Paper.pdf
  

  @inproceedings{larsson2020d,
    title = {The Strong Screening Rule for {{SLOPE}}},
    booktitle = {Advances in {{Neural Information Processing Systems}} 33},
    author = {Larsson, Johan and Bogdan, Malgorzata and Wallin, Jonas},
    editor = {Larochelle, H. and Ranzato, M. and Hadsell, R. and Balcan, M. F. and Lin, H.},
    date = {2020-12-06/0012},
    volume = {33},
    pages = {14592--14603},
    publisher = {{Curran Associates, Inc.}},
    location = {{Virtual}},
    url = {https://proceedings.neurips.cc/paper/2020/file/a7d8ae4569120b5bec12e7b6e9648b86-Paper.pdf},
    eventtitle = {Neural {{Information Procession Systems}} 2020},
    langid = {english}
  }
  

  Extracting relevant features from data sets where the number of observations n is much smaller then the number of predictors p is a major challenge in modern statistics. Sorted L-One Penalized Estimation (SLOPE)—a generalization of the lasso—is a promising method within this setting. Current numerical procedures for SLOPE, however, lack the efficiency that respective tools for the lasso enjoy, particularly in the context of estimating a complete regularization path. A key component in the efficiency of the lasso is predictor screening rules: rules that allow predictors to be discarded before estimating the model. This is the first paper to establish such a rule for SLOPE. We develop a screening rule for SLOPE by examining its subdifferential and show that this rule is a generalization of the strong rule for the lasso. Our rule is heuristic, which means that it may discard predictors erroneously. In our paper, however, we show that such situations are rare and easily safeguarded against by a simple check of the optimality conditions. Our numerical experiments show that the rule performs well in practice, leading to improvements by orders of magnitude for data in the p >> n domain, as well as incurring no additional computational overhead when n > p.

Theses

• Larsson, J. (2017). Gym-Based Exercise Therapy for Patients with Persistent Neck Pain: A Research Protocol for a Randomized Controlled Trial [Master’s thesis]. Lund university.
  

  @thesis{larsson2017,
    title = {Gym-Based Exercise Therapy for Patients with Persistent Neck Pain: A Research Protocol for a Randomized Controlled Trial},
    author = {Larsson, Johan},
    date = {2017-01-25},
    institution = {{Lund university}},
    location = {{Lund, Sweden}},
    pagetotal = {22},
    type = {Master's thesis}
  }
  
• Larsson, J. (2018). Eulerr: Area-Proportional Euler Diagrams with Ellipses [Bachelor thesis, Lund University]. http://lup.lub.lu.se/student-papers/record/8934042
  

  @thesis{larsson2018a,
    title = {Eulerr: Area-Proportional Euler Diagrams with Ellipses},
    author = {Larsson, Johan},
    date = {2018},
    institution = {{Lund University}},
    location = {{Lund, Sweden}},
    url = {http://lup.lub.lu.se/student-papers/record/8934042},
    editora = {Gustafsson, Peter},
    editoratype = {collaborator},
    pagetotal = {33},
    type = {Bachelor thesis}
  }
  

  Euler diagrams are common and intuitive visualizations for data involving sets and relationships thereof. Compared to Venn diagrams, Euler diagrams do not require all set relationships to be present and may therefore be area-proportional also with subset or disjoint relationships in the input. Most Euler diagrams use circles, but circles do not always support accurate diagrams. A promising alternative for Euler diagrams is ellipses, which enable accurate diagrams for a wider range of set combinations. Ellipses, however, have not yet been implemented for more than three sets or three-set diagrams where there are disjoint or subset relationships. The aim of this thesis is to present a method and software for elliptical Euler diagrams for any number of sets. In this thesis, we provide and outline an R-based implementation called eulerr. It fits Euler diagrams using numerical optimization and exact-area algorithms through two steps: first, an initial layout is formed using the sets’ pairwise relationships; second, this layout is finalized taking all the sets’ intersections into account. Finally, we compare eulerr with other software implementations of Euler diagrams and show that the package is overall both more consistent and accurate as well as faster for up to seven sets compared to the other R-packages. eulerr perfectly reproduces samples of circular Euler diagrams as well as three-set diagrams with ellipses, but performs suboptimally with elliptical diagrams of more than three sets. eulerr also outperforms the other software tested in this thesis in fitting Euler diagrams to set configurations that might lack exact solutions provided that we use ellipses; eulerr’s circular diagrams, meanwhile, fit better on all accounts save for the diagError metric in the case of three-set diagrams.
• Najafi, D., & Larsson, J. (2014). The Professional Role and Technology Use among Physical Therapists in Tokyo: A Qualitative Interview Study [Bachelor thesis, Lund University]. http://www.lunduniversity.lu.se/lup/publication/4523039
  

  @thesis{najafi2014,
    title = {The Professional Role and Technology Use among Physical Therapists in {{Tokyo}}: A Qualitative Interview Study},
    shorttitle = {The Professional Role and Technology Use among Physical Therapists in {{Tokyo}}},
    author = {Najafi, David and Larsson, Johan},
    date = {2014},
    institution = {{Lund University}},
    location = {{Lund, Sweden}},
    url = {http://www.lunduniversity.lu.se/lup/publication/4523039},
    urldate = {2017-06-20},
    pagetotal = {33},
    type = {Bachelor thesis}
  }