Background Systemic lupus erythematosus (SLE) has traditionally been viewed as a disease of women since the ratio of affected women to men is 9:1. Historically, men with SLE were thought to have more severe disease and worse prognosis than women, however, a 2013 review did not find compelling evidence that damage, disease activity or mortality is affected by sex. It concluded that the only consistent sex-based differences in SLE were lower rates of select disease manifestations such as alopecia.
Given this, it is plausible that the two sexes also respond to treatment differently, yet very few men have been included in clinical trials. Only 4% (n=9) of participants in published randomized controlled trials examining the impact of hydroxychloroquine (HCQ) on SLE were men. Thus, our objective was to examine the disease activity of both women and men with SLE treated with HCQ. In a cross-sectional analysis, we hypothesized that men with SLE would have higher disease activity than women based on average SLE Disease Activity Index (SLEDAI) 2K and Damage Index (DI) scores.
Methods Patient information was collected from the Canadian Network for Improved Outcomes in SLE (CaNIOS) database. All patients had an SLE diagnosis confirmed using the American College of Rheumatology (ACR) criteria. Inclusion in this study required that patients be ≥18 years of age and be currently taking any prescribed dosage regimen of HCQ. Data for these analyses were collected at entry into CaNIOS. Descriptive characteristics included health habits, ethnicity, immunosuppressant medication usage and SLEDAI 2K 10 day and DI scores. Sex differences in SLEDAI 2K and DI scores were analyzed using multivariate regression analyses controlling for prednisone use, current age, age at SLE onset and disease duration.
Results A total of 499 patients (n=57 men, n=442 women) treated with HCQ were included (table 1). Men appeared to have slightly lower SLEDAI 2K scores and higher DI scores than women, and had slightly higher use of prednisone. However, regression analyses revealed no differences in SLEDAI 2K scores between sexes, yet current age was significant (β=0.228, p=0.021). DI scores were significantly associated with current age (β=0.349, p=0.001) and disease duration (β=0.170, p=0.002) but not sex.
Conclusions In contrast to our hypothesis, we found no sex differences in disease activity or damage index between men and women. Results of this study are limited by lack of control for HCQ dose and duration of use which will be addressed in future analyses. Future analyses will investigate potential sex differences in longitudinal changes in SLEDAI and DI scores in response to ≥3 months of HCQ therapy.
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