Can pain cause high blood pressure?

Acute pain stimulates the sympathetic nervous system which increases blood pressure.^1,2 Studies that expose patients to painful stimuli, like immersing a hand in ice water,³ cutting off circulation to the forearm with a tourniquet-like action,⁴ and other noxious stimuli,⁵ have been shown to directly cause measurable sympathetic nerve activity. An increase in sympathetic activity is associated with an increase in blood pressure. Not surprisingly, in healthy individuals, acute pain has been shown to raise blood pressure in the immediate experience of pain. In some studies, the degree of perceived pain correlates with the extent of the rise in blood pressure.⁴

It has also been shown in numerous animal and human studies that people with high blood pressure have a higher pain threshold, a mechanism that is known as hypertension-associated hypoalgesia.^6–8 It is not yet clear if a low sensitivity to pain causes hypertension, or if high blood pressure causes the change in the perception of pain. In one study, people with normal blood pressure but a family history of hypertension were more likely to have a reduced sensitivity to pain suggesting that hypoalgesia might precede hypertension.⁹ Campbell et al. conducted a longitudinal study of the relationship between pain sensitivity and blood pressure.¹⁰ They measured 24-hour ambulatory blood pressure of 110 men at age 22. The same men had previously been assessed at age 14 for pain sensitivity and blood pressure. The authors found that pain sensitivity measured in adolescence predicted 24-hour systolic blood pressure at age 22 (r=0.37, p<0.01).

The relationship between the experience of chronic pain and blood pressure is less straight-forward. In a retrospective analysis, Bruehl et al. compared 300 randomly selected adults from a tertiary care pain management clinic with 300 adults in a general medicine practice from the same tertiary care center without chronic pain.¹¹ By reviewing the past medical records of patients in both groups, the authors found that hypertension was diagnosed in 39% of those in the pain group compared to 21% of the non-pain group (p<0.001), suggesting that chronic pain may be correlated with a risk of developing hypertension. Rates of hypertension in the non-pain group were similar to rates in the general population but were significantly higher in the pain group.

Maixner et al. compared 64 women with chronic temporomandibular pain to age- and gender-matched controls without pain.¹² Pain tolerance (thermal and ischemic) and blood pressure were measured in both groups. Blood pressure correlated with pain tolerance among the women in the pain-free group suggesting a hypertension-associated hypoalgesia. However, blood pressure did not influence pain tolerance among women with chronic pain. Those women were more sensitive to noxious stimuli. Although it is still not clear which came first, the authors suggest that chronic pain may result from an impairment in the pain regulatory systems that may be influenced by resting blood pressure.

^References

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