New Classification for an Old Problem: Chronic Pain in America

Almost 5% of Americans with chronic pain-or 10.6 million people-may suffer from debilitating high impact chronic pain (HICP), according to an NIH study by Pitcher and colleagues.[1] In 2016, the US National Pain Strategy (NPS) proposed the concept of HICP, which combines both disability and pain duration.[2] The term is intended to differentiate individuals with severe, debilitating chronic pain from those whose lives are less impacted by chronic pain.

“By addressing the multi-dimensionality of chronic pain, this classification will improve clinical practice, research and the development of effective health policy,” wrote first author Mark Pitcher, PhD, of the National Center for Complementary and Integrative Health, Bethesda, MD, and colleagues.[1] “[P]reventing the development of disability in this population should be a public health priority,” they added.

In light of the ongoing opioid epidemic, having a better understanding of the nature, impact, and extent of chronic pain in the US is important for control efforts.

To provide estimates on how many people in the US suffer from HICP, researchers analyzed data from 15,670 adult participants in the nationally representative 2011 National Health Interview Survey (NHIS).[3] In the current study, chronic pain was defined as pain experienced on most/every day for the last three months without activity limitations.[1] HICP was defined as pain on most/every day for the last three months with at least one activity limitation. Data on functional disability came from self-reported questionnaires. Results were controlled for age, sex, ethnicity, marital status, region, BMI, and chronic health conditions.

Key results
13.6%, or an estimated 29.9 million US adults, reported chronic pain without activity limitation
   • Chronic pain linked to over 4 times increased odds of disability (OR=4.43, CI 3.73-5.26)
4.8% with chronic pain, or an estimated 10.6 million US adults, reported HICP
   • More severe pain, with more mental health and cognitive impairments than chronic pain without limitation
   • Almost 85% not able to work
   • More likely to be over age 45, divorced/separated, with lower education level and more medical comorbidities

Patients with HICP were 12 times more likely to be unable to maintain self-care than those with chronic pain without activity limitation, and 5 times more likely to receive professional home care. Racial/ethnic disparities also existed, with African-Americans 76% more likely to report HICP compared with chronic pain without limitations. Likewise, Native Americans were 3 times more likely and Asian Indians were 3.5 times more likely to report HICP vs chronic pain without limitations. Limitations include the cross-sectional nature of the study, which cannot determine specific causes and contributors to HICP. Also, the NHIS only includes noninstutionalized individuals, and results may not generalize to veterans, prisoners, or those in residential care facilities, the latter of which may be at increased risk for HICP.

• Study suggests severe and debilitating high impact chronic pain (HICP) may affect 10.6 million Americans with chronic pain
• Almost 85% of those with HICP report being unable to work
• HICP is linked to more severe pain, and more mental health and cognitive impairments than chronic pain without limitation
• HICP is associated with being over aged 45 years, divorced/separated, lower education level, more medical comorbidities, and being African-American, Native American, and Asian Indian

References
1. Pitcher MH, Von Korff M, Bushnell MC, Porter L. Prevalence and Profile of High Impact Chronic Pain in the United States. J Pain. 2018 Aug 7 [Epub ahead of print].
2. National Pain Strategy: A Comprehensive Population Health-Level Strategy for Pain. Washington, DC: National Academies Press; 2016.
3. National Center for Health Statistics: National Health Interview Survey (NHIS) public use data release. NHIS survey description. Hyattsville, MD: National Center for Health Statistics; 2011.