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Prevalence of diabetes among patients with newly diagnosed rheumatoid arthritis (RA)

Posted by hsiunian on 03 Sep 2015 at 07:14 GMT

The authors reported that 18.8% of patients with newly diagnosed RA (i.e., incident cases) had diabetes, which is unusual given that the prevalence of diabetes in Taiwan's general adults is only 6.38% in 2008 (ref 1) and the risk of diabetes is approximately 50% higher in patients with RA than in general population (ref 2). Using the same national database (i.e., Taiwan's NHIRD), other researchers have reported a much lower prevalence of diabetes in newly diagnosed RA, ranging from 4.7% to 10.3% (ref 3-6). However, a higher prevalence of diabetes may be observed in prevalent cases of RA. For example, a Canadian study showed that the prevalence of diabetes in patients with RA increases from 10.8% at enrollment to 22.7% after 10 years (ref 7).

The use of the Longitudinal Health Insurance Database in 2005 (LHID2005)( may be inappropriate if the follow-up was started before 2005. According to the official statement regarding the database (, “LHID 2005 contains all the original claim data of 1,000,000 beneficiaries enrolled in year 2005 randomly sampled from the year 2005 Registry for Beneficiaries (ID) of the NHIRD, where registration data of everyone who was a beneficiary of the National Health Insurance program during the period of Jan. 1st 2005 to Jan. 1st, 2006 were drawn for random sampling.” Therefore, to be enrolled in the LHID2005, a beneficiary should be alive in 2005, which will introduce an immortal time bias when follow-up is started before that year. The bias is present, albeit likely small, because some patients had an index follow-up date beginning before 2005.

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No competing interests declared.