Disabilities are common, diverse, and associated with a wide range of functional limitations.1,2 Although their diversity means that individuals with disabilities have a broad variety of needs, the World Health Organization (WHO) classifies individuals with disabilities as a single population with impaired bodily or mental functioning, limitations in activity level, and/or restrictions in activity participation.3 This general conceptualization and classification of disabilities is also used by the Centers for Disease Control and Prevention (CDC) and the U.S. Census.4,5 In 2022, 28.7 % of adults in the U.S. reported having one or more disabilities, including 13.9 % with a cognition disability and 12.2 % with a mobility disability.6 It is important for clinicians to screen for disability not only to address a patient's functional needs but also the multiple serious comorbidities present in higher rates, including obesity, cardiovascular disease (CVD), and diabetes.6

Inflammation plays a key role in the development and progression of chronic diseases.7 Systemic chronic inflammation, a low-grade, persistent inflammation, damages blood vessels, tissues, and organs over time through oxidative stress, and is implicated not only in the pathways of diseases such as CVD and diabetes but also in mental health disorders.7,8 High-sensitivity C-reactive protein (hs-CRP), a widely used blood marker of inflammation, is a strong predictor of future cardiovascular events, as well as cardiovascular and all-cause mortality in the general population.9, 10, 11, 12, 13, 14 CRP has also been reported to be a biomarker of certain mental health disorders, such as major depressive disorder.15 Levels >3 mg/L generally indicate elevated systemic inflammation and an increased risk of future cardiovascular events, while levels >10 mg/L suggest markedly elevated inflammation.9,12,13,16, 17, 18 However, chronic inflammation is not a target of screening or treatment, which increases the potential health risks faced by vulnerable populations, including older adults and individuals with chronic conditions, who are more likely to have elevated hs-CRP levels.7,19,20 These vulnerable populations are also more likely to have disabilities, yet the relationship between disability and systemic inflammation remains underexplored. Existing studies examining the association between inflammation and disability have generally focused on specific chronic conditions or limited age groups, particularly geriatric populations, and the definitions of disability, and the criteria to define both disabilities and functional status in those studies have varied widely.21, 22, 23, 24, 25, 26, 27 Thus, it remains unclear whether adults with disabilities in the general U.S. population have elevated levels of systemic inflammation.

This study aims to determine, using a nationally representative sample of U.S. adults, whether individuals with disabilities are more likely to have elevated inflammation, as indicated by hs-CRP levels, compared to those without disabilities. In this study, disabilities are defined by the Washington Group Short Set on Functioning, an internationally validated tool that identifies individuals with disabilities based on functional limitations. In addition to examining overall associations between inflammation and disability, we will explore the associations between inflammation and both physical and mental disabilities. This study will provide an indication of the potential additional health risk faced across the wide range of patients with disabilities.