Childhood appendicitis halves the risk of ankylosing spondylitis
Appendicitis during childhood reduced the risk of developing ankylosing spondylitis (AS) later in life by almost half, while hospitalization with childhood respiratory tract infection (RTI) increased the risk, according to a study presented at the recent European League Against Rheumatism Annual Congress (EULAR 2016) held in London, UK.
The study analysed data from 2643 AS cases and 11,064 matched controls based on the Sweden national health care register from 1964 to 2009. Each indexed case was matched to five controls by age, sex, and county from the population register. [EULAR 2016, abstract OP0082]
Individuals hospitalized with either gastrointestinal, urogenital, appendicitis or respiratory tract infections before their 17th birthday were included, while those diagnosed with inflammatory bowel disease (IBD), rheumatic disease, iridocyclitis or psoriasis before age 17 were excluded.
Individuals with appendicitis during childhood were 40 percent less likely to be diagnosed with AS later in life (odds ratio [OR], 0.59, 95 percent confidence interval [CI], 0.42-0.82), while those who had been hospitalized with RTI during childhood were 20 percent more likely to develop AS (OR, 1.18, 95 percent CI, 1.01-1.39).
These relationships remained significant even after excluding all individuals diagnosed with IBD up to 2 years after the index case was first diagnosed with AS.
“These findings suggest the way the immune system responds during childhood, either by influencing the risk of a severe childhood infection or [through infection-induced changes in immunological response], may explain how AS develops,” said lead author Ulf Lindström from the Institute of Medicine at the Sahlgrenska Academy, University of Gothenburg in Gothenburg, Sweden.
Inflammatory responses triggered by childhood appendicitis could have immunologically modified the colonic mucosa, which protected these individuals from developing AS, he proposed.
In contrast, hospitalization for gastrointestinal tract or urogenital infections during childhood was not predictive of an AS diagnosis later in life.
Previous studies have implicated microbes exposure, in the form of gut flora or infection, in the development of several AS-related conditions including reactive arthritis and IBD. [Best Pract Res Clin Rheumatol 2014;28:687-702]
“Despite decades of effort to understand its aetiology, the causes of AS remain poorly characterised, so this is a significant development in helping us better understand this debilitating disease,” said Lindström.