The Relationship of Pain Intensity, Perceived Injustice, and Pain Catastrophizing to Heart Rate Variability In Naturally Occurring Acute Pain.

Objectives: Chronic pain disorders are among the most common and affect approximately 20% of the US population, leading to disproportionately high medical expenditures and negative economic impact. Behavioral factors of pain catastrophizing and perceived injustice are associated with pain intensity in chronic pain. Diminished heart rate variability (HRV) is also strongly associated with chronic pain. These factors have been less explored earlier in the pain experience and it is unclear whether they play a role in the transition from acute to chronic pain. The aim of this study was to determine the relationship between pain catastrophizing, perceived injustice, pain intensity and HRV in naturally occurring acute pain.

Methods: Ninety-seven subjects were recruited from local outpatient physical therapy clinics. Seated HRV was captured on ninety-four subjects via Polar chest strap while subjects were taking a survey via iPad. In addition to sociodemographic data, the survey included the Pain Catastrophizing Scale (PCS), Injustice Experience Questionnaire (IEQ), and Numeric Pain Rating Scale (NPRS). The natural log of high frequency power (lnHFP) HRV was used in the statistical analysis.

Results: Multiple regression modeling revealed that lower pain catastrophizing, higher perceived injustice, and lower pain intensity were associated with lower HRV, and accounted for 11.4% of the variance in HRV.

Discussion: While greater chronic pain intensity is associated with lower HRV, the relationship is reversed in the setting of acute pain. These findings highlight the need to better understand the unique factors that contribute to lower HRV in the acute phase.