Does high blood pressure reduce the risk of chronic low back pain? The Nord-Trøndelag Health Study.

BACKGROUND

Epidemiological studies have suggested inverse relationships between blood pressure and prevalence of conditions such as migraine and headache. It is not yet clear whether similar relationships can be established for back pain in particular in prospective studies.

METHODS

Associations between blood pressure and chronic low back pain were explored in the cross-sectional HUNT 2 survey of a Norwegian county in 1995-1997, including 39,872 individuals who never used antihypertensive medication. A prospective study, comprising 17,209 initially back pain-free individuals and 5740 individuals reporting low back pain, was established by re-examinations in the HUNT 3 survey in 2006-2008. Associations were assessed by logistic regression with respect to systolic, diastolic and pulse pressure, with adjustment for education, work status, physical activity, smoking, body mass and lipid levels.

RESULTS

In the cross-sectional study, all three blood pressure measures showed inverse relationships with prevalence of low back pain in both sexes. In the prospective study of disease-free women, baseline pulse pressure and systolic pressure were inversely associated with risk of low back pain [odds ratio (OR) 0.93 per 10 mm Hg increase in pulse pressure, 95% confidence interval (CI) 0.89-0.98, p = 0.007; OR 0.95 per 10 mm Hg increase in systolic pressure, 95% CI 0.92-0.99, p = 0.005]. Results among men were equivocal. No associations were indicated with the occurrence of pain in individuals with low back pain at baseline.

CONCLUSIONS

Results for low back pain are consistent with the theory of hypertension-associated hypalgesia, predicting diminished pain sensitivity with increasing blood pressure, possibly with modified reactions in people suffering from long-lasting pain.