Pain
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Randomized Controlled Trial
The hidden effects of blinded, placebo-controlled randomized trials: an experimental investigation.
The knowledge of having only a 50% chance of receiving an active drug can result in reduced efficacy in blinded randomized clinical trials (RCTs) compared to clinical practice (reduced external validity). Moreover, minor onset sensations associated with the drug (but not with an inert placebo) can further challenge the attribution of group differences to drug-specific efficacy (internal validity). We used a randomized experimental study with inert placebos (inert substance) vs active placebos (inducing minor sensations), and different instructions about group allocation (probability of receiving drug: 0%, 50%, 100%). ⋯ Moreover, minor drug onset sensations can challenge internal validity. Effect sizes for these mechanisms are medium, and can substantially compete with specific drug effects. For clinical trials, new study designs are needed that better control for these effects.
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Randomized Controlled Trial
Brain networks predicting placebo analgesia in a clinical trial for chronic back pain.
A fundamental question for placebo research is whether such responses are a predisposition, quantifiable by brain characteristics. We examine this issue in chronic back pain (CBP) patients who participated in a double-blind brain imaging (functional magnetic resonance imaging) clinical trial. We recently reported that when the 30 CBP participants were treated, for 2 weeks, with topical analgesic or no drug patches, pain and brain activity decreased independently of treatment type and thus were attributed to placebo responses. ⋯ Additionally, by means of frequency domain contrasts, we observe that at baseline, left dorsolateral prefrontal cortex high-frequency oscillations also predicted treatment outcomes and identified an additional set of functional connections distinguishing treatment outcomes. Combining medial and lateral prefrontal functional connections, we observe a statistically higher accuracy (0.9) for predicting posttreatment groups. These findings indicate that placebo response can be identified a priori at least in CBP, and that neuronal population interactions between prefrontal cognitive and pain processing regions predetermine the probability of placebo response in the clinical setting.
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Facial expressions during infancy are important to examine, as infants do not have the language skills to describe their experiences. This is particularly vital in the context of pain, where infants depend solely on their caregivers for relief. The objective of the current study was to investigate the development of negative infant facial expressions in response to immunization pain over the first year of life. ⋯ Instead, infants displayed a variety of generalized pain and distress faces aimed at gaining caregiver aid. The development of nonverbal communication in infants, particularly facial expressions, remains an important area of inquiry. Further study into accurately measuring infant negative emotions, pain, and distress is warranted.
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The objective of this study was to evaluate the time-series relationships between stress, sleep duration, and headache pain among patients with chronic headaches. Sleep and stress have long been recognized as potential triggers of episodic headache (<15 headache days/month), though prospective evidence is inconsistent and absent in patients diagnosed with chronic headaches (≥15 days/month). We reanalyzed data from a 28-day observational study of chronic migraine (n=33) and chronic tension-type headache (n=22) sufferers. ⋯ When patterns of stress or sleep were divergent across days, headache risk was increased only when the earlier day was characterized by high stress or poor sleep. As predicted, headache activity in the combined model was highest when high stress and low sleep occurred concurrently during the prior 2 days, denoting an additive effect. Future research is needed to expand on current findings among chronic headache patients and to develop individualized models that account for multiple simultaneous influences of headache trigger factors.
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Chronic pain is currently considered a public health problem with high costs to the individual and society. To improve prevention and treatment of chronic pain, epidemiologic studies are mandatory for assessing chronic pain. The aims of this study were to estimate the prevalence of chronic pain in the adult Danish population and to analyze associated factors such as diseases, immigration, and opioid use. ⋯ The study population consisted of 14,925 individuals in whom a high prevalence of chronic pain (26.8%, 95% confidence interval: 26.1 to 27.5) and a high prevalence of opioid consumption (4.5%) were observed. Other aspects of particular note: (1) a higher prevalence of chronic pain occurred among individuals with cardiovascular and chronic pulmonary diseases than among individuals with cancer; and (2) individuals with a non-Western background reported a higher pain prevalence, higher pain intensities, and more widespread pain than individuals with Danish background; however, opioids were more frequently used by native Danes. The prevalence of chronic pain as well as opioid use in Denmark are alarmingly high, and the relevance of opioid consumption is unknown.