ASCOT and Other Studies Show Some Surprising Findings

Chronic Pain Associated With Increased Prevalence of Hypertension

Chronic pain may be associated with an increased risk of hypertension, and early and aggressive management of chronic pain may have a beneficial impact on cardiovascular disease in this population, according to the results of a study from Vanderbilt University School of Medicine, Nashville, Tennessee.[5]

In healthy people, raised blood pressure is known to be associated with decreased sensitive-to-acute pain, but in individuals with chronic pain, such as chronic low back pain or chronic orofacial pain, elevated blood pressure is associated with increased acute pain responsiveness. Stephen Bruehl, PhD, and colleagues[5] speculated that this difference reflects failure of overlapping systems modulating pain and blood pressure. They conducted a retrospective review on randomly selected records of 300 patients with chronic pain evaluated at a university tertiary care pain center and 300 "nonpain" internal medicine patients seen at the same institution. The pain group patients, all aged < 65 years, had been evaluated for pain etiology, location, and duration, use of medications, clinical diagnosis of hypertension, and family history of hypertension. The nonpain group had no history of chronic pain or chronic headaches.

Statistical analysis revealed a significantly higher overall hypertension prevalence in the pain group compared with the nonpain group (39.3% vs 21.0%, P < .001), reflected by a similar significantly greater proportion of patients in the pain group taking antihypertensive medications compared with those in the nonpain group (35.7% vs 18.3%, P < .001). Similar differences were seen between the men and women in each group, although the difference between the women was twice as great compared with the men. Compared with prevalence of clinical hypertension in the US general population, according the third National Health and Nutrition Examination Survey (NHANES III),[6] there was no difference among men and women in the nonpain group, but in the pain group hypertension prevalence was significantly higher.

Chronic pain intensity, but not pain duration, was found to be a predictor of hypertension status, independent of the traditional risk factors for hypertension, such as older age, African American race, and a family history of hypertension.

Bruehl and colleagues[5] speculate that the association between elevated blood pressure levels and chronic pain reflects fundamental alterations in the relationship between the cardiovascular and pain regulatory systems in patients with chronic pain, possibly mediated by central alpha-2 adrenergic activity. Although a large proportion of the patients with chronic pain were taking antidepressant medications, they dismiss these as a possible cause of hypertension, as similar percentages of patients with and without hypertension in this group were taking these medications (55% and 40%, respectively). Another reason for excluding antidepressants as a possible cause of hypertension in this group is that they are more likely to be associated with hypotensive effects according to previous studies, the researchers note. However, they may have increased the likelihood of obesity, which could have contributed indirectly to the relationship between chronic pain and hypertension.

Bruehl and colleagues[5] point out that epidemiologic studies have reported that as many as 14% of the US population may be suffering from chronic pain,[7] so that even a small influence of chronic pain on hypertension could have a meaningful clinical impact.  Printer- Friendly Email This

Medscape Cardiology.  2005;9(1) ©2005 Medscape
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