The journal of pain : official journal of the American Pain Society
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Ample evidence suggests that sleep and pain are related. However, many questions remain about the direction of causality in their association, as well as mechanisms that may account for their association. The prevailing view has generally been that they are reciprocally related. The present review critically examines the recent prospective and experimental literature (2005-present) in an attempt to update the field on emergent themes pertaining to the directionality and mechanisms of the association of sleep and pain. A key trend emerging from population-based longitudinal studies is that sleep impairments reliably predict new incidents and exacerbations of chronic pain. Microlongitudinal studies employing deep subjective and objective assessments of pain and sleep support the notion that sleep impairments are a stronger, more reliable predictor of pain than pain is of sleep impairments. Recent experimental studies suggest that sleep disturbance may impair key processes that contribute to the development and maintenance of chronic pain, including endogenous pain inhibition and joint pain. Several biopsychosocial targets for future mechanistic research on sleep and pain are discussed, including dopamine and opioid systems, positive and negative affect, and sociodemographic factors. ⋯ This critical review examines the recent prospective and experimental research (2005-present) on the association of sleep and pain in an attempt to identify trends suggestive of directionality and potential mechanisms. An update on this literature is needed to guide future clinical efforts to develop and augment treatments for chronic sleep disturbance and chronic pain.
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Observational Study
General health status and incidence of first-onset temporomandibular disorder: the OPPERA prospective cohort study.
Temporomandibular disorder (TMD) overlaps with other health conditions, but no study has examined which of these conditions increase the risk of developing first-onset TMD. The authors prospectively evaluated the relationship between health status at enrollment and subsequent incidence of TMD in 2,722 men and women. Participants aged 18 to 44 years had no history of TMD and were clinically free of TMD when enrolled in 2006 to 2008 at 4 U.S. study sites in the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) prospective cohort study. First-onset examiner-classified TMD developed in 260 people over a median 2.8 years of follow-up. Cox regression estimated the association between health conditions and TMD incidence while accounting for potential confounders. Incidence of first-onset TMD was 50% higher for people with low back pain (adjusted hazard ratio [AHR] = 1.50, 95% confidence limits [CLs]: 1.08, 2.10) and 75% higher for people with genital pain symptoms (AHR = 1.75, 95% CLs = 1.04, 2.93) than people without a history of these pain disorders. Digit ratio, a marker of intrauterine exposure to sex hormones, was significantly associated with TMD incidence. Other independent predictors of first-onset TMD were sleep disturbance and cigarette smoking. These findings reveal multiple influences of health status on incidence of first-onset TMD. ⋯ This article examines health conditions that commonly overlap with TMD to determine which ones predict first-onset TMD. A history of low back pain and genital pain conditions at baseline were important predictors. Novel findings were that disrupted sleep and conditions in utero may increase incidence of first-onset TMD.
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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.