Men with ankylosing spondylitis typically reported a better quality of life than women but experienced worse radiographic damage over time, a prospective cohort study found.
During a mean follow-up of 8.3 years, male gender was associated in a multivariable analysis with a lower score on the Ankylosing Spondylitis Quality of Life index (ASQoL), signifying a better quality of life (β= -1.18, 95% CI -2.17 to -20, P=0.02), according to Astrid van Tubergen, MD, PhD, of Maastricht University Medical Center in the Netherlands, and colleagues.
Nonetheless, males had greater progression on the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) (β=8.24, 95% CI 4.38-12.09, P<0.01), the researchers reported online in Rheumatology.
However, there were no gender-attributable differences in disease activity or physical function, “suggesting that other determinants like psychological factors may contribute to quality of life in ankylosing spondylitis,” they stated.
Ankylosing spondylitis has long been considered a disease primarily of men, with an estimated gender ratio of 9:1.
However, recent studies have indicated that this is a misconception, and that the male to female ratio is in the range of 2 to 3:1.
In addition, recent research has suggested the possibility of gender-associated differencesin disease features and outcomes.
“Awareness of these gender-attributable differences is … important and could lead to a better understanding of the disease course and the outcomes for female patients with ankylosing spondylitis in particular, who have been underreported in the past,” the researchers wrote.
To examine these possible differences, van Tubergen and colleagues analyzed data from the Outcome in Ankylosing Spondylitis International Study, a longitudinal study that has enrolled 216 patients from France, Belgium, and the Netherlands since 1996.
The cohort comprised 154 men and 62 women. At baseline, women were older (46.8 versus 42.3 years, P=0.02), had longer symptom duration (13.4 versus 10.8 years, P=0.03), and greater delay in diagnosis (10.8 versus 8 years, P=0.04).
Women also scored higher at baseline on several disease activity scores, such as the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI; 3.9 versus 3.2, P=0.03), tender joint counts (4.4 versus 2.7, P<0.01), and enthesitis index (16.6 versus 8.2, P<0.01).
In contrast, men had higher baseline scores on the mSASSS (13.8 versus 6.5, P=0.02) and higher C-reactive protein levels (CRP; 19.5 versus 14.2 mg/L, P=0.04).
On a univariate analysis assessing disease over time, men had lower BASDAI scores (β= -0.67, 95% CI -1.25 to -0.10, P=0.02) but higher CRP levels (β=4.82, 95% CI 1.45-8.20, P<0.01). However, on another disease activity rating, the Ankylosing Spondylitis Disease Activity Score, which also incorporates the CRP and is considered a more accurate reflection of disease activity than the BASDAI, scores were not different between men and women.
There also were no significant differences between men and women on physical function over time.
On the univariate analysis, men also were found to have higher scores on the mental component of the Short Form-36, which remained significant in the multivariate analysis (β=5.84, 95% CI 2.21-9.48, P<0.01).
This difference in the mental component of the SF-36, which assesses the mental and psychological aspects of quality of life, suggests that women might “perceive more impairment in their activities and participation in life compared with men,” the authors noted.
Men and women also might experience pain differently, according to the researchers.
“It is likely that gender-attributable differences regarding quality of life in ankylosing spondylosis are not only determined by biologic factors, but also by psychological factors,” they wrote.
They also suggested that the worse radiographic outcomes seen among men might reflect mechanical influences, with “physically demanding occupational activities [having] been shown to be associated with more radiographic damage in patients with longstanding ankylosing spondylitis.”
Limitations of the study included some loss to follow-up in the study cohort, the relatively low number of women included, and longstanding disease in the majority of patients.