In ankylosing spondylitis (AS), smoking is an independent risk factor for hip involvement, even including exposure to less than 10 pack-years, according to a study published in The Journal of Rheumatology. Patients with AS with (N=103) and without hip involvement (N=89, controls) were compared. Sensitivity analysis, subgroup analysis, and logistic regression analysis were conducted to estimate the link between smoking and hip involvement in AS. The study group observed that patients with juvenile-onset AS (JAS) who had cigarette exposure were male, younger, or had peripheral arthritis history were prone to hip involvement. In AS, after adjusting for confounding factors, cigarette smoking (aOR, 7.23; 95% CI, 2.27-23.05), JAS (aOR, 2.52; 95% CI, 1.26-5.06), and male sex (aOR, 2.89; 95% CI, 1.14-7.33) were found to be independently linked with hip involvement. Additionally, compared with those with no exposure to 10 pack-years (aOR, 2.21; 95% CI, 1.09-4.47), patients who smoked with exposure of less than 10 pack-years were 2.2 times more likely to have hip involvement. This correlation was replicated in subgroup analyses of propensity score-matched subjects and males and withstood sensitivity analysis.
