Previous research has established that patients with ankylosing spondylitis (AS) have a significantly increased risk for myocardial infarction and stroke compared to control patients without AS. In this study, researchers sought to determine whether diabetes mellitus played a role in this association. The Taiwan National Health Insurance Program database was queried for data spanning 2005–2012; patients aged 20–84 years with a new AS diagnosis (AS group), identified based on International Classification of Diseases, Ninth Revision code (ICD-9 code 720.0), were age- and sex-matched 1:4 to patients without a diagnosis of AS (non-AS group). The primary outcome measure was a new diabetes mellitus diagnosis (ICD-9 code 250). Overall, diabetes mellitus incidence was significantly higher in the AS group than the non-AS group (1.43 vs. 1.19 per 100 person-years, 95% CI 1.02 to 1.43, P=0.025). The authors stated that the reason why diabetes mellitus was more prevalent in patients with AS than those without AS was beyond the scope of the study, but they suggested that AS patients may be more likely to receive a diagnosis because they receive more clinical care than patients without AS. Therefore, they are more likely to undergo evaluation including blood glucose levels. Diabetes mellitus in non-AS patients could be under-identified. The researchers called for more studies to determine whether the relationship because AS and diabetes mellitus is causal.