Smoking ups prevalence of hip involvement in ankylosing spondylitis

Cigarette smoking is independently associated with a higher prevalence of hip joint involvement in ankylosing spondylitis (AS), suggests a study.

“[E]ven exposure of less than 10 pack-years could contribute to increased prevalence of hip involvement in AS, which underlines the significance of smoking cessation in patients with AS, especially for juvenile-onset AS (JAS),” the investigators said.

A real-world case-control study was conducted to compare AS patients with and without hip joint involvement, as defined by the Bath Ankylosing Spondylitis Radiology Hip Index. The investigators carried out logistic regression, subgroup, and sensitivity analyses to explore the relationship between smoking and hip involvement in AS.

In total, 103 patients with hip involvement (cases) and 89 without (control) were included in the analyses. Univariate analysis revealed a higher risk of hip involvement in patients who had JAS, were younger, were male, had a history of peripheral arthritis, or had cigarette exposure.

After adjusting for confounders, the following risk factors correlated independently with hip involvement in AS: JAS (adjusted odds ratio [aOR], 2.52, 95 percent confidence interval [CI], 1.26‒5.06), male sex (aOR, 2.89, 95 percent CI, 1.14‒7.33), and cigarette smoking (aOR, 7.23, 95 percent CI, 2.27‒23.05).

In addition, patients who smoked and had exposure of less than 10 pack-years had a 2.2-fold greater chance to have hip involvement in AS relative to those without (aOR, 2.21, 95 percent CI, 1.09‒4.47). This association was also observed in the subgroup analyses of males and propensity score‒matched patients. It also persisted in the sensitivity analysis.