The risk of ischaemic heart disease (IHD), and in particular myocardial infarction (MI), is increased amongst patients with established rheumatoid arthritis (RA). Few studies have included contemporary patients with RA. We recently reported that the risk of IHD is not elevated before the onset of RA symptoms. However, when, in relation to RA diagnosis, the risk is increased is unknown.
To assess the risk of MI and other IHD events amongst patients diagnosed with RA during the last decade and within 18 months following RA symptom onset, compared to the general population, by time since RA diagnosis, year of RA diagnosis and by rheumatoid factor (RF) status.
A Swedish inception cohort of RA (n = 7469) diagnosed between 1995 and 2006 and a matched general population comparator cohort (n = 37,024), was identified and linked to national registers of morbidity and mortality from IHD. Relative risks (RRs) of MI and other IHD events were estimated using Cox regression.
During follow-up, 233 patients with RA and 701 controls developed a first MI, corresponding to an overall RR of MI of 1.6 (95% confidence interval 1.4, 1.9). Increased risks of MI were already detected within 1-4 years following RA diagnosis, as well as in patients diagnosed with RA during the last 5 years, in RF-negative patients and for transmural as well as nontransmural MIs.
MI risk increases rapidly following RA diagnosis, suggesting the importance of additional mechanisms other than atherosclerosis. The elevated short-term risk is present amongst patients diagnosed in recent years, underscoring the importance of MI prevention from the time of RA diagnosis.