Differences in sex ratios have since long been recognized in several common chronic diseases and are particularly common in rheumatic diseases, inflammatory as well as non-inflammatory.

The present presentation will focus on gender in some of the most frequent rheumatic disorders - rheumatoid arthritis, systemic lupus erythematosus and ankylosing spondylitis. The predictive ability of gender in these common rheumatic diseases will be reviewed and possible confounding issues considered.

Rheumatoid arthritis (RA) In RA the female:male ratio is about 2-3:1. Already in the year 1800 Augustin Jacob Landré-Beauvais described the female preponderance in a group of patients who probably had RA. Since long women are believed to run a more serious disease course than men. In recent years, several long-term studies have shown that women have higher DAS28, more pain, worse HAQ and lower remission rates compared with men. However, observational studies over 2, 5 and 8 years have shown that joint damage assessed by radiographic scoring was similar in men and women. This inconsistent situation may be explained by the fact that pain, unrelated to the inflammatory process, confounds the interpretation of the values obtained for DAS or DAS28. This may give rise to overestimation of the disease activity and possibly result in suboptimal treatment.

A common cause of such non-inflammatory pain is fibromyalgia (FM), a common co-morbidity in RA with pronounced female preponderance (about 9:1). FM in patients with RA has been found to be an independent predictor of DAS28 and may therefore confound the evaluation of disease activity.

Systemic lupus erythematosus (SLE) SLE displays a striking female predominance, 9:1 in childbearing age. Of interest, men seem to be at risk of a worse outcome compared with women. Thus, male sex has turned out to be a predictor of serious kidney involvement. Moreover, disease severity including more cardiovascular and renal disease was reported to be more pronounced in men. Furthermore, in childhood SLE, boys were reported to have a higher prevalence of severe renal disease and poorer outcome. These studies suggest that gender is a predictor of both disease expression and severity and should be taken into account in the often difficult choice of treatment strategy in patients with SLE.

Ankylosing spondylitis (AS) AS has a male preponderance estimated to about 3:1. Gender differences in disease profile and disease course have been described with more low back spondylitis and more radiographic changes in men and more involvement of neck and peripheral joints in women. Furthermore, studies have suggested that women have higher disease activity and develop more functional impairment than men. However, further studies using different assessment methods produced diverging results. Moreover, active disease, measured by objective markers, and male gender predicted benefit from biologic drugs while active disease, assessed by subjective markers, and female gender did not. Thus, gender may predict disease expression and response to therapy in AS although the evaluation of disease activity may be confounded by the available assessment methods.

Conclusions In rheumatic diseases gender differences in disease prevalence are striking. Gender may predict disease expression, course and outcome and should be taken into account in clinical trials and observational studies as well as in clinical practice. In addition, the possibility that assessment instruments containing non-disease specific components may confound the evaluation of the disease should be acknowledged and stimulate to the development of more specific instruments.

Disclosure of Interest None Declared