New study finds low risk of stroke after spinal manipulation

An analysis of Medicare claims data from older Americans who sought care for neck pain from chiropractors suggests that cervical spine manipulation is unlikely to cause stroke.

This new study was published in the February 2015 edition of the Journal of Manipulative and Physiological Therapeutics.

According to a web post by the National Center for Complementary and Integrative Health (NCCIH), an arm of the U.S. National Institutes of Health, this is the first population-based study in the U.S. to examine the risk of stroke after spinal manipulation and the first such study on older adults. It was conducted by researchers from Dartmouth College and the Southern California University of Health Sciences, and was supported by the NCCIH.

The purpose of the study was to quantify risk of stroke after chiropractic spinal manipulation, as compared to evaluation by a primary care physician, for Medicare beneficiaries aged 66 to 99 years with neck pain.

The safety of cervical spinal manipulation (i.e., manipulation of the vertebrae in the neck) for neck pain has been questioned because previous observational research found an association between visits to a health-care practitioner and subsequent vertebrobasilar stroke (VBS). VBS is an uncommon type of stroke involving the arteries that supply blood to the back of the brain. Although those researchers ultimately attributed the association between health-care visits and VBS to the likelihood that people with torn vertebrobasilar arteries seek care for related headache and neck pain before their stroke, controversy regarding the safety of cervical spinal manipulation persists.

In this new study, researchers analyzed Medicare claims on more than 1.1 million people aged 66 to 99 who visited a chiropractor or primary care physician to treat neck pain. They then noted the occurrence of first stroke after the office visit and compared the hazard of stroke within 30 days for the two groups: patients visiting chiropractors and those visiting primary care physicians.

The specific incidence of VBS was too small to report. The researchers found that the incidence of any type of stroke among all patients was extremely low. For patients who saw a chiropractor, the risk of stroke was significantly lower at seven days compared to the patients who saw a primary care physician (1.2 per 1,000 vs. 1.4 per 1,000); but at 30 days, there was a slight elevation in risk for the chiropractic patients (5.1 per 1,000 vs. 2.8 per 1,000). However, the researchers noted that these small differences in risk were of doubtful clinical significance.