Browsing by Author "Palacios-Derflingher, Luz Maria"
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- ItemOpen AccessConditional Dependence in Joint Modelling of Longitudinal Non-Gaussian Outcomes(2016-01-07) Roy, Mili; de Leon, Alexander R.; Ambagaspitiya, Rohana; Palacios-Derflingher, Luz Maria; Sun, BingruiThe thesis is motivated by the limitations of conventional joint modelling strategies based on linear and generalized linear mixed models (LMMs/GLMMs). The class of so-called Gaussian copula mixed models (GCMMs), introduced by Wu and de Leon (2014) to generalize conventional LMMs/GLMMs to non-Gaussian settings, was adopted, and simulations were conducted to investigate the impact of incorrectly ignoring the conditional dependence between outcomes, given the random effects, on the performance of maximum likelihood estimates (MLEs). A variety of scenarios involving shared or correlated random effects were considered, and implementation of the correct and misspecified joint models was done in SAS’s PROC NLMIXED. Although MLEs of fixed effects were only slightly impacted by the conditional independence misspecification, MLEs based on the correct GCMM yielded generally better performances than those from the incorrect model. Data on pediatric pain (Weiss, 2005; Withanage et al., 2015) were used for illustration.
- ItemOpen AccessAn Economic Evaluation of Body Checking Policies in Bantam Ice Hockey(2019-01-25) Lee, Raymond; Currie, Gillian R.; Marshall, Deborah A.; Emery, Carolyn A.; Palacios-Derflingher, Luz MariaSport-related injury is the leading cause of injury in youth and are costly to the healthcare system. Disallowing body checking in Pee Wee (ages 11-12) ice hockey has been found to be effective in reducing the risk of injuries and associated healthcare costs, however the impact on injury risk and costs in Bantam (ages 13-14) remains unknown. The objectives of this study are to compare injury rates and costs between non-elite (lower 70% divisions of play) Bantam players in leagues allowing body checking to where body checking is disallowed, and to project the overall change on the number of injuries and costs to the Alberta healthcare system if body checking were disallowed for all Bantam players over one season. The study found that disallowing body checking reduced injuries by 4.32/1000 player-hours and saved cost by $1,737/1000 player-hours in the public healthcare system. This policy change could potentially prevent 1,102 injuries that occur during games and save $331,522 in the public healthcare system over one season in Alberta. However, this study used injury rates adjusted only for exposure hours and team clustering, but not other covariates or repeated observations. Thus further analysis is required before policy recommendations can be made.
- ItemOpen AccessEstimation of probabilities for latent bernoulli variables: a model for in-vitro fertilization(2008) Palacios-Derflingher, Luz Maria; Ehlers, Peter F.
- ItemOpen AccessIdentifying the Impact of Injury Definition and Training Load on the Study of Jumper’s Knee(2016) MacDonald, Kerry; Meeuwisse, Willem; MacKenzie, Don; Emery, Carolyn; Palacios-Derflingher, Luz Maria; Ronsky, JanetWith a growing body of research into volleyball injuries we are beginning to understand potential risk factors for the most prevalent injuries. Volleyball has been found to have more overuse than acute injuries, yet the majority of research to date has failed to utilize an injury definition sensitive enough to capture the true frequency and burden of overuse problems. Furthermore, the mechanism of overuse injuries is believed to be a chronic overloading of tissue, in combination with an incomplete healing process. With advancements in technology, it is now possible to accurately and efficiently measure these loads which, in turn, could have significant impact on injury prevention. Previously identified risk factors were assessed with the purpose of developing a sport-specific screening program. The impact of injury definition on the data collection for overuse injuries was also examined. This analysis evaluation confirmed the need to use specific overuse injury definitions, with an improved sensitivity for the capture of overuse injury frequency and burden compared to more conventional time-loss definitions. An assessment of known risk factors, including a measure of jumping load, was completed with the more sensitive overuse injury capture. Although no risk factor was found to significantly predict injury outcome, several methodological challenges were identified. This research demonstrates that traditional assessment techniques that have been used for time-loss injuries are not sufficient for overuse injury capture and analyses. The contribution of this dissertation to the literature is the demonstration that the methods presented can more accurately capture the injury burden and record the specific load metrics for that injury. However, further advancements in statistical analysis for prevalence measures of injury are required to assess dynamic risk factors, including measures of load, for overuse injuries.
- ItemOpen AccessIncidence, Risk Factors, and Mechanisms of Concussion and Musculoskeletal Injury in Youth Soccer Players(2019-01-18) Codd, Chevonne; Schneider, Kathryn J.; Emery, Carolyn A.; Yeates, Keith Owen; Palacios-Derflingher, Luz Maria; Reed, NickolasObjective: Assessment of incidence, risk factors, and mechanisms of concussion and musculoskeletal (MSK) injuries in youth soccer players over one outdoor season of play. Methods: Prospective cohort study conducted. Participants completed a pre-season baseline questionnaire (demographic and injury history questions). A team safety advocate collected exposure and injury data. Results: A sample of 361 players (10-18 years) participated. Most injuries were reported in games (37 MSK, 24 concussions). MSK and concussions occurred at a rate (/1000player hours) of 5.47 (95%CI:2.99-9.18) and 3.12 (95%CI:0.13-6.16), respectively in males and 5.26 (95%CI: 3.33-7.89) and 3.66 (95%CI: 2.09-5.94), respectively in females. In a univariate model, female sex [IRRmsk=1.18(95% CI:1.02-1.36), IRRconc=1.18(95%CI:1.02-1.36)], previous concussion [IRRconc=1.07(95%CI:1.01-1.15)], higher level of play [IRR: 1.02(Tier II) to 0.63(Tier IV), reference Tier I] and older age group [IRR:1.48(U13) to 1.72(U14), reference U12] were risk factors for MSK injury and/or concussion. Conclusions: Injuries and concussions are common in youth soccer players.