Pain
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Review Meta Analysis
Racial and ethnic differences in experimental pain sensitivity: Systematic review and meta-analysis.
Our objective was to describe the racial and ethnic differences in experimental pain sensitivity. Four databases (PubMed, EMBASE, the Cochrane Central Register of Controlled Trials, and PsycINFO) were searched for studies examining racial/ethnic differences in experimental pain sensitivity. Thermal-heat, cold-pressor, pressure, ischemic, mechanical cutaneous, electrical, and chemical experimental pain modalities were assessed. ⋯ Estimates did not vary by pain modalities, nor by other demographic factors; however, SMDs were significantly different based on the sample size. Racial/ethnic differences in experimental pain sensitivity were more pronounced with suprathreshold than with threshold stimuli, which is important in clinical pain treatment. Additional studies examining mechanisms to explain such differences in pain tolerance and pain ratings are needed.
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Cutaneous inflammation alters the function of primary afferents and gene expression in the affected dorsal root ganglia (DRG). However, specific mechanisms of injury-induced peripheral afferent sensitization and behavioral hypersensitivity during development are not fully understood. Recent studies in children suggest a potential role for growth hormone (GH) in pain modulation. ⋯ These effects may be mediated through an upregulation of insulin-like growth factor 1 receptor (IGFr1) as GH modulated the transcriptional output of IGFr1 in DRG neurons in vitro and in vivo. Afferent-selective knockdown of IGFr1 during inflammation also prevented the observed injury-induced alterations in cutaneous afferents and behavioral hypersensitivity similar to that after GH pretreatment. These results suggest that GH can block inflammation-induced nociceptor sensitization during postnatal development leading to reduced pain-like behaviors, possibly by suppressing the upregulation of IGFr1 within DRG.
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Persons with Alzheimer disease (AD) commonly present with chronic nonmalignant pain, but long-term use of opioids among this population has not been studied previously. Our aim was to investigate the prevalence of long-term (≥180 days) use of opioids for nonmalignant pain and associated factors among community-dwelling persons with AD and to compare the prevalence with a matched cohort without AD. The Medication use and Alzheimer's disease (MEDALZ) cohort was used for this study, comprising all community-dwelling persons diagnosed with AD in Finland during 2005 to 2011 and their matched comparison persons without AD. ⋯ Factors associated with long-term opioid use included AD, age ≥80 years, female sex, rheumatoid arthritis, osteoporosis, low socioeconomic position, history of substance abuse, and long-term benzodiazepine use. Prevalence of long-term opioid use was somewhat similar among both groups. Among persons with AD, long-term opioid use was strongly associated with transdermal opioids.
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The processing of reward and reinforcement learning seems to be important determinants of pain chronicity. However, reward processing is already altered early in life and if this is related to the development of pain symptoms later on is not known. The aim of this study was first to examine whether behavioural and brain-related indicators of reward processing at the age of 14 to 15 years are significant predictors of pain complaints 2 years later, at 16 to 17 years. ⋯ The relationship of pain complaints and activation in the periaqueductal gray and ventral striatum depended on the T-allele of rs563649. Carriers of this allele also showed more pain complaints than CC-allele carriers. Therefore, brain responses to reward outcomes and higher sensitivity to pain might be related already early in life and may thus set the course for pain complaints later in life, partly depending on a specific opioidergic genetic predisposition.