Prior evidence suggests that persons experiencing chronic headaches also suffer from frequent backaches and other pain conditions, although reasons for the association remain unclear. New evidence from a study conducted in Germany helps to confirm a higher prevalence of lower-back pain in persons with chronic migraine or tension-type headaches than among persons who do not regularly suffer headaches.
Writing in the journal PAIN, Min-Suk Yoon — from the Department of Neurology, University Hospital of Essen, Germany — and colleagues report that the objective of their study was to evaluate associations between frequent lower-back pain and chronic headache in a large, German population-based sample of persons [Yoon et al. 2013]. Among 18,000 persons who were randomly selected from 3 regions in Germany to participate in a mail and telephone-interview survey, there were 9,944 respondents for whom data were collected.
On average, respondents were 43 (±13) years of age and 53% were female. Headaches were diagnosed by participant self-report according to International Classification of Headache Disorders-2nd edition (ICHD-2) criteria and categorized as to frequency (episodic 1–14 days/month or chronic ≥15 days/month) and headache subtype (migraine or tension-type). “Frequent low-back pain” was classified as self-reported low-back pain ≥15 days/month on average during the 3 months prior to the survey date. Results indicated the following:
- 56% of respondents (5,605/9,944) reported headache in the previous year and 4.5% (255/5,605) of them had chronic headache.
> Migraine was diagnosed in 52% (2,933) of respondents with headache, of whom about 6% (182) had chronic migraine.
> Tension-type headache was diagnosed in 22% (1,253) of respondents with headache, and 4% (50) of those reported chronic tension-type headache.
- 61% of respondents (6,030/9,944) reported low-back pain, of whom 21% (1,267/6,030) reported frequent low-back pain.
After adjusting for sociodemographic covariates — eg, age, sex, smoking status, alcohol use — the odds of having frequent low-back pain were between 2.1 (95% CI 1.7-2.6) and 2.7 (95% CI 2.3-3.2) times higher in persons with episodic headache subtypes — migraine or tension-type — than in persons not experiencing headache. In persons experiencing chronic headache subtypes the odds of having frequent low-back pain were much greater; between 13.7 (95% CI 7.4-25.3) and 18.3 (95% CI 11.9-28.0) times higher when compared with no headache.
Therefore, it appears that persons experiencing chronic headache, whether migraine or tension-type, are at greatly increased risk of also suffering from frequent lower-back pain. The likelihood of low-back pain occurring in association with episodic headaches was significant, but of less magnitude. In a separate, exploratory analysis, the researchers also found that the use of acute-pain medications was highly associated with both back pain and headache status, especially among persons with frequent low-back pain.
Multiple explanations may contribute to the association of headache and back pain, the researchers speculate, including the notion that the neurobiology of chronic headache, independent of primary headache type, not only involves the trigeminal pain pathway, but is also a part of abnormal pain processing overall. Neuroimaging studies have discovered functional and structural changes in the brains of persons with chronic migraine, and many of these same changes also appear in persons with other chronic pain conditions, including chronic back pain.
COMMENTARY: Essentially, this was a cross-sectional epidemiological study of the prevalence of either low back pain or frequent low back pain — occurring during the 3-months prior to the survey — in a population-based sample of persons exposed to migraine or tension-type headache. The researchers point out that this broad approach was better than an assessment of a clinic-based dataset — ie, surveying patients in clinical treatment settings — because the latter might reflect the most severe spectrum of headache and/or low back pain and, therefore, would be subject to bias.
The high prevalences of headache (56%) and low-back pain (61%) in the population seem surprising. However, the researchers claim these values are consistent with the international literature on the subject. Still, it is important to consider in this study by Yoon et al.  whether the target sample of 18,000 persons was truly representative of the entire population at risk of headache and back pain. And, even if this was so, were the 55% who actually participated in the study a random representation of the targeted sample?
A common problem in epidemiological studies relying on voluntary responses to surveys is a possible selection bias, whereby the very young and the very old might not participate, and persons more affected by the health issue of interest may respond more eagerly and frequently than unaffected healthy persons. This alone might have skewed results in the present study, and it also may account for the sometimes wide-ranging prevalence rates across various other studies of this nature examining different pain disorders.
Despite such concerns, it might be assumed in well-designed and executed studies such as this one by Yoon et al. that, while the magnitude of the relationship estimates might deviate somewhat from “true” values, the direction of the trends probably reflects the actual situation in the population at risk for headache and lower-back pain. An appreciation of a strong comorbid association of chronic headache, whether migraine or tension-type, with frequent low-back backache suggests that both conditions must be addressed simultaneously for successful pain management outcomes. And, as the researchers note, “patients with [these] comorbidities may have different responses to treatment paradigms than those patients experiencing only one condition.”
REFERENCE: Yoon M-S, Manack A, Schramm S, et al. Chronic migraine and chronic tension-type headache are associated with concomitant low back pain: Results of the German Headache Consortium study. PAIN. 2013(Mar);154(3): 484–492 [abstract here].
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