Occupational, personal and psychosocial resources for preventing persistent low back pain

The aim of this prospective cohort study was to identify modifiable protective factors of the progression of acute/subacute low back pain (LBP) to the persistent state at an early stage to reduce the socioeconomic burden of persistent LBP. Patients attending a health practitioner for acute/subacute LBP were assessed at baseline addressing occupational, personal and psychosocial factors, and followed up over 12 weeks. Pearson correlations were calculated between these baseline factors and the presence of nonpersistent LBP at 12-week follow-up. For those factors found to be significant, multivariate logistic regression analyses were performed. The final 3-predictor model included job satisfaction, mental health and social support. The accuracy of the model was 72%, with 81% of nonpersistent and 60% of persistent LBP patients correctly identified. Further research is necessary to confirm the role of different types of social support regarding their prognostic influence on the development of persistent LBP.

Prognostic occupational factors for persistent low back pain in primary care

To reduce the socio-economic burden of persistent low back pain (LBP), factors influencing the progression of acute/subacute LBP to the persistent state must be identified at an early stage.

Occupational maxillofacial fractures: a 3-year survey in central Switzerland

PURPOSE: The aim of this study was to determine occupational facial fractures in central Switzerland. Concomitant injuries were also studied. MATERIALS AND METHODS: The Department of Cranio-Maxillofacial Surgery at the University Hospital in Berne provides a 24-hour maxillofacial trauma service for its population (1.6 million). The present study was comprised of 42 patients (8.4% of treated maxillofacial injuries) with occupational maxillofacial fractures registered at this unit between 2000 and 2002. Information on the topic of occupation, the cause of the accidents, and the topographic location of the fractures was analyzed. RESULTS: The mean age of the patients was 44.4 years, with a male to female ratio of 41:1. Sixty-nine percent of the injuries occurred in farm and forestry workers and in construction laborers during the summertime (33%). Workers in these occupations carried a 127-fold (farm and forestry workers) and a 44-fold (construction laborers) higher risk of incurring maxillofacial fractures than did service and office workers. Injuries were most frequently (43%) caused by a thrown, projected, or falling object. Eighty-two percent of the fractures occurred in the midface region and at the skull base. Fifty-nine percent of the patients had concomitant injuries. In 69%, surgery was necessary, the mean duration of their hospital stay being 4.8 days. CONCLUSION: The probability of sustaining work-related maxillofacial traumata is correlated to the nature of the occupation. Farm and forestry workers are at the highest risk, most frequently injured by being struck by an object or an animal. The introduction of personalized safety measures should become obligatory in high-risk occupations.

Concordance Probability and Discriminatory Power in Proportional Hazards Regression

The concordance probability is used to evaluate the discriminatory power and the predictive accuracy of nonlinear statistical models. We derive an analytic expression for the concordance probability in the Cox proportional hazards model. The proposed estimator is a function of the regression parameters and the covariate distribution only and does not use the observed event and censoring times. For this reason it is asymptotically unbiased, unlike Harrell's c-index based on informative pairs. The asymptotic distribution of the concordance probability estimate is derived using U-statistic theory and the methodology is applied to a predictive model in lung cancer.

Tests for Comparing Mark-Specific Hazards and Cumulative Incidence Functions

It is of interest in some applications to determine whether there is a relationship between a hazard rate function (or a cumulative incidence function) and a mark variable which is only observed at uncensored failure times. We develop nonparametric tests for this problem when the mark variable is continuous. Tests are developed for the null hypothesis that the mark-specific hazard rate is independent of the mark versus ordered and two-sided alternatives expressed in terms of mark-specific hazard functions and mark-specific cumulative incidence functions. The test statistics are based on functionals of a bivariate test process equal to a weighted average of differences between a Nelson--Aalen-type estimator of the mark-specific cumulative hazard function and a nonparametric estimator of this function under the null hypothesis. The weight function in the test process can be chosen so that the test statistics are asymptotically distribution-free.Asymptotically correct critical values are obtained through a simple simulation procedure. The testing procedures are shown to perform well in numerical studies, and are illustrated with an AIDS clinical trial example. Specifically, the tests are used to assess if the instantaneous or absolute risk of treatment failure depends on the amount of accumulation of drug resistance mutations in a subject's HIV virus. This assessment helps guide development of anti-HIV therapies that surmount the problem of drug resistance.