Background A growing body of evidence suggests that there are associations between perinatal factors or early life exposures and later development of chronic inflammatory diseases. For ankylosing spondylitis (AS), previous studies have found increased risks associated with birth order and childhood respiratory tract infections, while breast-feeding and childhood appendicitis have been found protective.

Objectives To identify early life risk factors for AS, with focus on perinatal characteristics and childhood infections.

Methods People with AS from the Swedish National Patient Register, born 1973-2004, were matched 1:5 on age, sex, and place of residence to general population controls. Conditional logistic regression was used to compare odds ratios for AS in relation to potential risk factors identified in the Medical Birth Register and the National Patient Register.

Results People with AS (n=5427) had significantly more hospitalizations for infections before age 16 compared to controls (n=21523), and had more often gone through a tonsillectomy (table 1). People with AS were also more likely to be born in the winter months, and to have an older sibling, while having a sibling overall (older or younger) resulted in an odds ratio for AS of 1.01 (0.93-1.11). No association was seen with factors such as maternal age, Caesarean delivery, or a 1 SD change in weight for gestational age (table 1). Odds ratios for AS associated with being born small or large for gestational age (>2 SD below or above sex-specific mean weight) was 1.10 (0.93-1.30) and 0.89 (0.74-1.08), respectively. In line with previous data, childhood appendectomy was associated with an odds ratio <1, but the estimate did not reach statistical significance.

Conclusion Childhood exposures related to infections seem to play a role in later development of AS, while factors generally associated with foetal growth do not.

REFERENCES: NIL.

Acknowledgements: NIL.

Disclosure of Interests None Declared.