Pain in AS May Be Caused by Sources Other Than Spine Inflammation, Opioid Study Suggests

Pain in patients with ankylosing spondylitis (AS) may stem from factors other than spinal inflammation, researchers said after discovering that the main subjective factors of disease activity were associated with the use of opioid medication.

Researchers found that particularly chronic opioid use did not relate to any objectively measurable disease activity factors. Instead, subjective disease activity scores and self-reported depression were linked to opioid use in these patients, according to a study in The Journal of Rheumatology.

Many AS patients find medicines that are typically used to manage their condition are insufficient to control pain. Meanwhile, there are no recommendations on the use of opioids in these patients, the research team from McGovern Medical School at the University of Texas Health Science Center Houston noted.

This deficit of recommendations is likely caused by a lack of studies concerning opioid use in AS patients. To fill this knowledge gap, in the study “Opioid Analgesic Use in Patients with Ankylosing Spondylitis: An Analysis of the Prospective Study of Outcomes in an Ankylosing Spondylitis Cohort,” researchers aimed to examine the characteristics of opioid-treated AS patients.

The study also looked into the use of other psychoactive medications used together with opioids.

Analyzing 706 AS patients for at least two years, the study found that the majority of patients had never used opioids. Only 9.5 percent were chronically taking opioids, while 21.7 percent took opioids occasionally.

Patients treated with opioids were generally older and less often employed, particularly those treated in a chronic manner. They were also more likely to have smoked and they exercised less. They had been ill longer and had a higher number of other medical conditions, like cardiovascular disease.

Patients taking opioids reported more severe subjective functional impairment, measured by the BASFI (Bath Ankylosing Spondylitis Functional Index). They also had worse disease activity according to the subjective BASDAI (Bath Ankylosing Spondylitis Disease Activity Index). The highest scores were seen in patients using opioids in a chronic manner.

Patients on these strong pain drugs also had poorer general health, both according to their own assessment and by validated measures. While most of these factors were subjective, those who used opioids chronically had worse disease severity when assessed by imaging of the spine.

In contrast, measures of inflammation, such as C-reactive protein and erythrocyte sedimentation rate, did not indicate worse disease activity. These measures were not linked to opioid use, researchers said.

Typical AS medications, such as non-steroid anti-inflammatory drugs (NSAIDs), disease-modifying drugs such as sulfasalazine, or TNF-blockers were equally used by patients with or without opioid treatment. Antipsychotic or stimulant medications also did not differ between the groups. Those using opioids, however, more often used anxiolytics, which are used to treat anxiety disorders; antidepressants; and sleeping pills.

A statistical analysis, taking all these factors into account, showed that poor general health worsens depression, and that subjectively assessed impairment and disease activity were linked with opioid use.

The data indicate that pain in AS is not linked to inflammation in the spine alone, researchers said. But they did admit that current measures of inflammation may not be adequately capturing the disease processes in the spine.

Nonetheless, it is crucial to further examine whether pain in AS is due to inflammation, nerve damage, or possibly psychological factors, they said.

“Opioid usage was more likely to be associated with subjective measures (depression, BASDAI, BASFI) than objective measures (CRP [C-reactive protein] and ESR [erythrocyte sedimentation rate]), suggesting that pain in AS may derive from sources other than spinal inflammation alone,” the team concluded.