Objective: To define the sex ratio of juvenile onset ankylosing spondylitis (AS) among a large population.
Methods: Using a standard questionnaire, data were collected from 3362 subjects, members of the National Ankylosing Spondylitis Society and patients at a tertiary referral center.
Results: Of 3362 patients, 2461 (73%) were male; male:female sex ratio was 2.7:1. Of the total, 379 (11%) had disease onset between the ages of 5 and 16 years. Of these, 278 were boys and 101 girls, giving an overall male:female ratio, in juvenile AS, of 2.6:1. For those with onset ages 5-13 years there was a ratio of 2.1:1, while for those aged over 14 years at onset, the ratio was 3.2:1.
Conclusion: Older published ratios, ranging from 4.5:1 to 6:1, used smaller samples, focusing only on subjects who were juveniles at the time of the study. Our data collection method, which recruits from 2 sources and includes adults with juvenile onset, attempts to avoid these methodological problems. The data suggest a higher incidence of juvenile AS among females than previously described.