OBJECTIVE: This article investigates the role of pain in disability trends in the United States, within the context of recent unfavorable disability trends and the concurrent rise in pain.
METHODS: We conducted a two-part analysis using National Health Interview Survey data from 2002 to 2018 for US adults aged 45-84. First, we assessed how changes in the prevalence of five site-specific types of pain (headaches/migraines, joint, low back, neck, and facial/jaw pain) associate with disability trends. Second, we used self-reported causes of disability and examined whether there has been a change in the proportion of individuals who attribute their disability to one of five chronic or acute painful conditions.
RESULTS: The five site-specific types of pain, individually and collectively, were significantly associated with increases in disability. If site-specific chronic pain had not increased during the study period, the trend for functional limitations would have been 40% lower, and that for activity limitations would have shown a slight decline instead of an increase. Attributions of functional limitations to painful conditions increased by 23% during the 2002-2018 period, representing an additional 9.82 million Americans experiencing pain-attributable disability. Arthritis/rheumatism, back/neck problems, and other musculoskeletal/connective conditions were the primary sources of pain-related disability.
CONCLUSIONS: Our research provides the first systematic, national examination of how pain is contributing to disability trends in the United States. The findings have implications for disability reduction policies and shed light on the far-reaching consequences of pain for overall population health.

Musculoskeletal pain is a common cause of pain in adolescence and can be an important predictor of future pain. The prevalence of hip or groin pain that could potentially affect different adolescent populations has not yet been systematically reviewed. This systematic review aimed to determine the prevalence of hip or groin pain in this population. Five electronic databases were searched until January 2019 for eligible studies that included males and females 13 to 19 years of age. Study selection, data extraction, and risk of bias assessments were completed by 2 independent researchers. Based on inclusion criteria, 8 population-based, 8 clinical, and 4 sports populations were included. Studies were conducted in Europe, North America, and Australia. The prevalence was dichotomized into \"0 to 3 months\" and \"3 months and above.\" Meta-analyses were performed to estimate the prevalence from 0 to 3 months, and individual estimates were reported for studies of 3 months and above. The overall prevalence of hip or groin pain in all adolescents from 0 to 3 months was 12% (95% confidence interval [CI] 6%, 23%) based on 10 studies, and was 7% (95% CI 6%, 10%) based on 7 population studies. Caution should be applied to these estimates due to substantial study heterogeneity. The pain prevalence in cerebral palsy from 0 to 3 months based on 4 studies was 13% (95% CI 10%, 15%). Individual prevalence estimates were 6% and 31% in obese and 4% in hypermobility populations, respectively, and ranged from 6% to 100% in 4 sports studies. The validity of these estimates is compromised by poor methodological quality.

Pharmacological approaches to our understanding and treatment of pain have had a long history and have traditionally relied on very few drugs that either have significant side effects and abuse liability, such as the nonsteroidal anti-inflammatory drugs or the opioids, respectively, or those that have been developed for other conditions such as the tricyclic antidepressants. The pathophysiology of pain is undoubtedly complex, complicated in part by the fact that it is not a singular condition, and has a variety of etiologies and a number of associated comorbidities that make treatment interventions challenging. Moreover, there are changes in the central nervous system during the course of the development of chronic pain that, in a manner parallel to neurodegenerative disorders, likely require different pharmacological approaches in the early stages of acute pain compared to those that would be effective when pain has become chronic. This chapter reviews the current status of the field of pain research focusing on some relatively underdeveloped areas, such as pain and its associated comorbidities, and the use of transgenic animals and drug self-administration procedures in the context of analgesic assessment. This chapter also incorporates more recent developments and emerging trends in the area of epigenetics, biomarkers, and the use of induced pluripotent stem cells for pharmacological evaluation, target identification, and validation. Recent progress in the study of \"organs-on-a-chip\" will also be included in this overview, setting expectations for future progress that integrates these advances for deeper insights into mechanisms, novel treatments, and facilitated efforts in drug discovery.