Background/Purpose:

Subjects with rheumatoid arthritis (RA) are at a higher risk of developing cardiovascular (CV) disease which is the leading cause of death in subjects with RA. In the general population, there is unequivocal evidence supporting ASA as secondary prophylaxis for CV events, but its efficacy as primary prevention has been questioned. There is currently no consensus regarding use of ASA as primary prophylaxis and it is necessary to identify if its use is justified in particular risk profile groups. We performed a case-crossover study in RA subjects, to evaluate if a protective association exists between ASA use and myocardial infarction (MI).

Methods:

THIN, a population-based UK database, containing data provided from general practitioners was used. We included records between 1/1/1995 and 9/30/2013. In the UK persons over age 60 get free ASA by prescription and 75% of use is by prescription. Subjects >60 years with RA, defined as one RA read code and one DMARD code within a year, constituted our study population. We excluded all subjects with history of MI, angina prior to study initiation or a coronary artery procedure (stent/coronary artery bypass graft) prior to the index date. To be included subjects had to have an incident MI/angina or a fatal MI. Each subject contributed two observations: a “case observation” and a “control observation”. For “case observations”, the index date was the MI/angina date. For “control observations”, the control date was 90 days prior to the index date. An individual was considered exposed if he/she used ASA within 7 days prior to the index date/control date. In addition, we examined effect of ASA use within 15 and zero days prior to the event. A conditional logistic regression was performed adjusting for drugs that are potential confounders (antiaggregants-anticoagulants, antihypertensives, NSAIDS, lipid-lowering drugs, glucocorticoids, nitrates). A sensitivity analysis was performed looking at males. As a secondary outcome we looked at MI and fatal MI.

Results:

We identified 705 RA patients who experienced incident MI/angina during the study period. The characteristics of the study subjects are described in Table 1. During the case period 192 subjects were exposed to ASA and during the control period 156 subjects were exposed, with 96 discordant exposure statuses within a subject in the two observation periods. There was no significant association between ASA use and CV events after adjusting for potential confounders (1.20 (0.73, 1.96)). When analysis was restricted to men, we again found no association was present (adjusted OR 1.12 (0.49, 2.52)). Findings were similar when considering MI as our outcome and when restricting exposure to 15 and zero days prior to the index date.

Conclusion:

This study suggests ASA is not effective in RA as primary prophylaxis.

Table 1. Study population characteristics.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/primary-prevention-of-myocardial-infarction-in-rheumatoid-arthritis-using-low-dose-aspirin-a-case-crossover-study/