Background Ankylosing Spondylitis (AS) is a chronic inflammatory disorder primarily involving the axial skeleton. It starts predominantly before the age of 30 and the hallmark for the diagnosis is the detection of sacroiliitis on x-rays. Estimates of the prevalence of AS ranges from 0.03% and 1.8% in Europe1. However, there is limited data on the prevalence of radiographically verified sacroiliitis.
Objectives To estimate the prevalence of moderate to severe radiographically verified sacroiliitis (grade 3-4) in a population based study of elderly men and compare the health status in those with and without sacroiliitis.
Methods A population survey for the study of risk factors for osteoporosis (MrOS)2 including 1005 men 69-81 years old, randomly identified from the regional population registry was used. X-rays of the pelvis and spine were examined by two readers and the prevalence of grade 3-4 sacroiliitis, syndesmophytes and spondylophytes were ascertained. Self-administered questionnaire registered data on demographics, anthropometrics, lifestyle, physical activity (PASE), functional status (IADL items), quality of life (SF-12) and back health (pain, Quebec Pain Disability Scale items).
Results Fourteen cases with grade 3-4 sacroiliitis were identified corresponding to a prevalence of 1.4% (95%CI: 0.7-2.4). There were 7 with sacroiliitis grade 3 bilaterally, 4 with grade 4 bilaterally, 1 with grade 3 involvement at one SI-joint and grade 4 at the other and only 1 with unilateral grade 3 involvement. All patients with sacroiliitis had either syndesmophytes and/or bridges or degenerative changes in the spine. The majority (8/14) had both types of changes, 4 had no syndesmophytes and 2 no spondylophytes. There were no major differences between the two groups regarding demographics, anthropometric measures and smoking status. Furthermore, there were no significant differences with regard to health status, physical activity or quality of life, although a tendency towards impaired functional status was observed among those with sacroiliitis. The majority of individuals with sacroiliitis did not report major difficulties related to back problems.
Conclusions The prevalence of moderate to severe (grade 3-4) radiographically verified sacroiliitis was 1.4% in a population of elderly men in Sweden. Self-reported health was only slightly different in those with sacroiliitis, suggesting that the relative impact of AS is modest at this age group.
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Disclosure of Interest None Declared