Hypertension in Chronic Pain: Risk Factors

In patients with chronic pain, comorbid hypertension may be mediated by reduced heart rate variability and spontaneous baroreflex sensitivity, according to the results of a recent study published in Pain.

In this analysis of data from the prospective Tromsø Study, researchers evaluated the responses to Tromsø 6, a survey performed in 2007 and 2008. The study included 8204 participants who underwent the cold pressor test, which was used to derive heart rate variability and spontaneous baroreflex sensitivity by beat-to-beat blood pressure recordings. Clinically meaningful chronic pain was categorized as persistent daily pain ≥3 months with a severity at least 3 out of 10 on a numeric rating scale.

Of the 8204 participants, 1421 experienced clinically meaningful chronic pain, while 5640 were considered pain free. The remainder of participants did not meet the inclusion criteria for either group.

Heart rate variability time domain measures (Standard Deviation of the Normal-to-Normal Intervals [SDNN], P =.004; root mean square of the successive differences of the inter-beat intervals [rMSSD], P =.003), heart rate variability frequency (HF Power, P <.001), and baroreflex sensitivity pre-cold pressor test (P =.03) were mediated by chronic pain status after adjustment. During post-cold pressor test evaluation, only the heart rate variability time domain measures (SDDN, P =.01; rMSSD, P =.008) and baroreflex sensitivity (P =.01) were significantly associated with chronic pain status.

Usual pain intensity and number of pain sites were significantly correlated with all measures of pre-cold pressor test heart rate variability and spontaneous baroreflex sensitivity. In the post-cold pressor test evaluations, pain intensity only correlated with the SDNN time measure of heart rate variability, and number of pain sites only correlated with the rMSSD time measure of heart rate variability.

Based on the self-reported hypertensive status of patients, the researchers found that reduced heart rate variability and spontaneous baroreflex sensitivity had significant indirect effects on the presence of comorbid hypertension.

The study authors concluded that “presence of [broadly-defined chronic pain] was associated with decreased [heart rate variability] and [spontaneous baroreflex sensitivity] relative to absence of chronic pain, independent of potential confounds.” The researchers acknowledge that the effect sizes were relatively small, but they explained that the results “consistently supported a model in which risk for hypertension in the [chronic pain] population derives in part from diminished [heart rate variability] and [spontaneous baroreflex sensitivity].”

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Reference

Bruehl S, Olsen RB, Tronstad C, et al. Chronic pain-related changes in cardiovascular regulation and impact on comorbid hypertension in a general population: the Tromsø study [published online September 25, 2017]. Pain. doi: 10.1097/j.pain.0000000000001070