The journal of pain : official journal of the American Pain Society
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Observational Study
Study protocol, sample characteristics, and loss to follow-up: the OPPERA prospective cohort study.
When studying incidence of pain conditions such as temporomandibular disorder (TMD), repeated monitoring is needed in prospective cohort studies. However, monitoring methods usually have limitations and, over a period of years, some loss to follow-up is inevitable. The OPPERA prospective cohort study of first-onset TMD screened for symptoms using quarterly questionnaires and examined symptomatic participants to definitively ascertain TMD incidence. During the median 2.8-year observation period, 16% of the 3,263 enrollees completed no follow-up questionnaires, others provided incomplete follow-up, and examinations were not conducted for one third of symptomatic episodes. Although screening methods and examinations were found to have excellent reliability and validity, they were not perfect. Loss to follow-up varied according to some putative TMD risk factors, although multiple imputation to correct the problem suggested that bias was minimal. A second method of multiple imputation that evaluated bias associated with omitted and dubious examinations revealed a slight underestimate of incidence and some small biases in hazard ratios used to quantify effects of risk factors. Although "bottom line" statistical conclusions were not affected, multiply-imputed estimates should be considered when evaluating the large number of risk factors under investigation in the OPPERA study. ⋯ These findings support the validity of the OPPERA prospective cohort study for the purpose of investigating the etiology of first-onset TMD, providing the foundation for other papers investigating risk factors hypothesized in the OPPERA project.
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Observational Study
Changes in opioid prescribing for Washington workers' compensation claimants after implementation of an opioid dosing guideline for chronic noncancer pain: 2004 to 2010.
An opioid overdose epidemic emerged in the United States following increased opioid prescribing for chronic noncancer pain. In 2007, Washington State agencies implemented an opioid dosing guideline on safe prescribing for chronic noncancer pain. The objective of this population-based observational study was to evaluate opioid use and dosing before and after guideline implementation. We identified 161,283 workers aged 18 to 64 years with ≥1 opioid prescriptions in Washington Workers' Compensation, April 1, 2004, to December 31, 2010. Prevalence and incidence rates of opioid use were assessed. We compared pre- and postguideline chronic and high-dose use (≥120 mg/d) among incident users. The mean monthly prevalence of opioid use declined by 25.6% between 2004 (14.4%) and 2010 (10.7%). Fewer incident users went on to chronic opioid therapy in the postguideline period (4.7%; 95% confidence interval [CI], 4.5-5.0%) than in the preguideline period (6.3%; 95% CI, 6.1-6.6%). Compared with preguideline incident users, postguideline incident users were 35% less likely to receive high doses (adjusted odds ratio = .65; 95% CI, .59-.71). Although the extent to which decreases were due to the guidelines is uncertain, to our knowledge, this is the first report of significant decreases in chronic and high-dose prescription opioid use among incident users. ⋯ Evidence-based strategies for opioid risk management are needed to help abate the epidemic of opioid-related morbidity and mortality. The study findings suggest that opioid dosing guidelines that specify a "yellow flag" dosing threshold may be a useful tool in preventing escalation of doses into ranges associated with increased mortality risk.
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To assess the longitudinal gray matter (GM) and white matter (WM) changes between repeated observations 1 year apart in a group of the early clinical stage of migraine patients without aura, and to explore the relationship of such structural changes with headache activity, we studied patients newly diagnosed with episodic migraine lasting 8 to 14 weeks. Optimized voxel-based morphometry and tract-based spatial statistical analyses were used to evaluate changes in GM and WM by using 3-dimensional T1-weighted and diffusion-tensor imaging, respectively. At the 1-year follow-up examination, GM reduction was observed in the dorsolateral and medial part of the superior frontal gyrus, orbitofrontal cortex, hippocampus, precuneus, and primary and secondary somatosensory cortices. No significant differences were found in the fractional anisotropy and longitudinal, radial, and mean diffusivity of WM in migraine patients without aura within a year. Negative results were found for the association between changes in headache activity parameters and GM. Our results indicated that the GM and WM changed in different pathophysiological conditions of migraine patients without aura. The WM probably evolves slowly in the course of migraine chronicity. ⋯ Our study found early involvement of GM reduction of sensory-discriminative brain regions in the pathologic process of migraine, but the WM did not exhibit significant changes in the same time interval. GM reduction in sensory-discriminative brain regions may characterize the pathophysiological features of migraine patients without aura in its early stage.
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Comparative Study
Comparative responsiveness of verbal and numerical rating scales to measure pain intensity in patients with chronic pain.
Verbal rating scale (VRS) and numerical rating scale (NRS) are regularly used to assess and monitor pain in chronic pain patients. Although the NRS has been generally preferred, limited comparative responsiveness evidence was reported. This study compared the responsiveness of VRS and NRS measuring current pain and investigated the influence of different references (ie, worst, least, average, and current pain or their composite) on the NRSs' responsiveness. Two hundred fifty-four chronic pain patients attended a 10-day pain self-management program and were assessed with two 6-point VRSs (assessing current pain) and four 11-point NRSs (assessing worst, least, average, and current pain) at pre- and posttreatment. A patient-reported rating of pain improvement was used as the criterion for standardized response mean and receiver operating characteristic curve analyses. Results showed that the VRSs and NRSs exhibited small responsiveness in all patients, but the magnitude of responsiveness became moderate to large in patients with improved pain. However, in patients with pain improvements, the NRS current pain item and composite score (made up of the 4 pain items) were found to have significantly larger responsiveness and greater discriminatory ability to detect the presence of improvement than other current pain VRSs and the NRSs assessing worst, least, and average pain. Potential implications for clinical practice are discussed. ⋯ This study shows that the current pain and composite NRSs were more responsive than the current pain VRSs and the NRSs measuring other individual pain references in patients with improved pain, undertaking a short-term, self-management program. The results help inform the selection of pain intensity measures in studies using similar types of intervention.
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Factors contributing to pain following surgery are poorly understood, with previous research largely focused on adults. With approximately 6 million children undergoing surgery each year, there is a need to study pediatric persistent postsurgical pain. The present study includes patients with adolescent idiopathic scoliosis undergoing spinal fusion surgery enrolled in a prospective, multicentered registry examining postsurgical outcomes. The Scoliosis Research Society Questionnaire-Version 30, which includes pain, activity, mental health, and self-image subscales, was administered to 190 patients prior to surgery and at 1 and 2 years postsurgery. A subset (n = 77) completed 5-year postsurgery data. Pain prevalence at each time point and longitudinal trajectories of pain outcomes derived from SAS PROC TRAJ were examined using analyses of variance and post hoc pairwise analyses across groups. Thirty-five percent of patients reported pain in the moderate to severe range presurgery. One year postoperation, 11% reported pain in this range, whereas 15% reported pain at 2 years postsurgery. At 5 years postsurgery, 15% of patients reported pain in the moderate to severe range. Among the 5 empirically derived pain trajectories, there were significant differences on self-image, mental health, and age. Identifying predictors of poor long-term outcomes in children with postsurgical pain may prevent the development of chronic pain into adulthood. ⋯ This investigation explores the prevalence of pediatric pain following surgery, up to 5 years after spinal fusion surgery. Five pain trajectories were identified and were distinguishable on presurgical characteristics of age, mental health, and self-image. This is the largest study to examine longitudinal pediatric pain trajectories after surgery.