Atopy is associated with osteoarthritis severity: results from the KHOALA cohort

Atopy has been identified as a risk factor for osteoarthritis, but without specifying its impact on disease severity. We sought to investigate the association between atopy and the symptomatic and structural severity of knee and hip osteoarthritis.

We used data from KHOALA, a French multicentre cohort of patients with knee and/or hip osteoarthritis (OA) investigating "atopic" subjects, defined as those with history of asthma and/or atopic dermatitis (AD) compared to "non-atopic" subjects. We compared: WOMAC pain, stiffness and function scores; and the proportion of having end-stage knee and/or hip radiographic OA (Kellgren Lawrence grade 4). Besides, we studied the cumulative incidence of total knee replacement (TKR) over 7 years of follow-up in patients with knee osteoarthritis in atopic versus non-atopic patients. Linear regression analyses of WOMAC sub-scores were adjusted for age, sex, BMI and GHQ-28 score (psychological well-being), whereas logistic regression and Cox regression analyses of radiographic end-stage disease and TKR were adjusted for age, sex and BMI.

The cohort comprised 66 atopic subjects (46 with asthma, 16 with AD and 4 having both) and 651 non-atopic subjects with a mean age of 65.2 years, 68% of whom were women, and a mean BMI of 29.3 kg/m². Atopy was associated with an increased risk of end-stage radiographic OA (adjusted OR 2.46 (1.42 to 4.25), P = 0.001), with 42% of atopic patients having Kellgren Lawrence grade 4 compared with 24% of non-atopic patients. Furthermore, over a 7-year follow-up period, atopy was associated with a two-fold increase in the risk of TKR, with an HR of 1.99 (95% CI: 1.15 to 3.45; P =0.01). Atopy was significantly associated with an increase in WOMAC pain score (7.6/20 ± 3.8 versus 6.4/20 ± 4; P < 0.05) but this association became non-significant after adjustment. Atopy was not associated with worse functional limitations or stiffness.

Atopy appears to be associated with the radiographic OA severity and increased requirement of knee joint replacement. These results invite us to consider atopy as a potential new determining factor in the OA disease severity.