Participants in Clinical Trials on Chronic Back or Neck Pain Are Not Representative of the Larger Patient Population

Populations that experience health disparities are frequently underrepresented in spine pain clinical trials, according to an analysis of data from eight randomized controlled trials (RCTs) of spinal manipulation for chronic back or neck pain. Funded by the National Center for Complementary and Integrative Health, this analysis was conducted by researchers from the University of Minnesota and North Dakota State University and was published in the journal BMC Musculoskeletal Disorders.

RCTs are regarded as the gold standard study design for evaluating treatment effectiveness, involving random assignment of participants to different groups to minimize bias and assess intervention impact. However, studies of this type are sometimes criticized for generalizability issues. For example, how well do the people participating in the trial represent the larger community of people receiving care in real-world settings? The generalizability of RCT populations is important because it potentially limits the applicability of RCT findings to influence clinical practice and policy.

Low-back pain is the leading cause of disability burden worldwide, yet no previous published studies have assessed the representativeness of populations enrolled in RCTs for spinal pain (i.e., back and/or neck pain) in the United States. To address this gap, researchers analyzed eight RCTs involving a total of 1,444 participants conducted between 1994 and 2012, all focusing on spinal manipulation for chronic spine pain, and compared the trial participants with a representative sample of U.S. adults with chronic spine pain. Given that all trials involved chiropractic spinal manipulation, the team also compared the trial participants with U.S. adults with chronic spine pain who received chiropractic care. 

The analysis revealed significant underrepresentation of health disparity populations, including racial and ethnic minority groups, less educated individuals, and the unemployed, in the RCTs compared with the U.S. population with spine pain. The clinical trials disproportionately included more White participants (8.5 percent more), while having fewer participants from Asian or Pacific Islander (1 percent less), Black (7.3 percent less), and Hispanic (8 percent less) backgrounds.  

Unemployed individuals were underrepresented by 24.9 percent in the trials, and people with a bachelor’s, postgraduate, or professional degree were overrepresented. Overall, the clinical trials overrepresented people who were middle to high income, employed, educated, and White. Additionally, trial participants tended to have shorter duration of spinal pain, better mental health, and better physical health. And while the odds of chiropractic use in the United States are lower for individuals from health disparity populations, the trials also underrepresented these populations relative to the larger population of people with spine pain who receive care from chiropractors.

This is the first analysis to compare demographic and clinical characteristics of spinal pain clinical trial participants with those of the broader U.S. population with spine pain. It indicates that despite ongoing efforts to enhance diversity in clinical trials, many trials continue to fall short. There are many factors that contribute to the low participation of health disparity populations in clinical research, and among them is the burden of clinical research participation (e.g., transportation, financial, and time demands). To foster change, the authors recommended that spine pain researchers consider employing community-based strategies that have shown promise for increasing research participation of health disparity populations, such as engaging key community members throughout the research process, pilot testing recruitment approaches, and placing enrollment and treatment sites in underserved communities to reduce travel burden.