An epidemiological study suggests that use of low-dose aspirin as primary prevention is associated with a lower cardiovascular and all-cause mortality.

The study authors comment that the place of low-dose aspirin as primary prevention against cardiovascular disease (CVD) in people with type 2 diabetes is uncertain. They therefore used data from an existing diabetic population cohort based in Fremantle, Australia (the Fremantle Diabetes Study, FDS) to examine whether low-dose aspirin use was associated with any significant effects on mortality. The study population was identified from one area of Fremantle between 1993 and 1996, and participants were assessed at baseline and annually using a comprehensive questionnaire and physical examination. For this study, those with no history of CVD at baseline were followed until death or study cut-off in June 2007. Primary outcomes were CVD and all-cause death according to low-dose aspirin use.

The recorded population of the study area at the time of recruitment was 120,097 people; of these, 2,258 were identified as diabetic during the recruitment period and 1,426 (63%) were recruited to the FDS. There were 1,294 with type 2 diabetes: 651 of these had no CVD history at baseline. Mean duration of follow-up was 11.6 years (7,537 patient-years). During this period, 160 patients died (24.6%), 70 of them of cardiovascular causes (43.8% of deaths).

In an unadjusted analysis, there was no association between low-dose aspirin use and CVD (P = 0.52) or all-cause P = 0.94) death. After adjustment for confounding factors, a significant association was observed between aspirin use and both CVD and all-cause mortality (hazard ratio [HR] 0.30; 95% CI, 0.09 to 0.95, and 0.53; 95% CI, 0.28 to 0.98, respectively; P ≤ 0.044).

The authors conclude that in this patient population, regular aspirin use was associated with reduction in both CVD and all-cause mortality. As a result, they suggest that all patients with type 2 diabetes should receive low-dose aspirin, except those with the lowest risk.

[Editor’s comment: not so fast! While this study appears to have been carried out to a reasonable standard, it’s an epidemiological study with a relatively small population and few outcome events. The confidence intervals are wide, and the P value only just under the conventional level of significance. Finally, the results conflict with those of a recent robust meta-analysis of controlled trial data that involved over 10,000 people with diabetes and which found no clear benefit from primary prevention in this patient group (BMJ 2009; 339: b4531). An editorial accompanying the meta-analysis pointed out that aspirin was associated with a reduction in risk, albeit one that was not statistically significant. This was consistent with the relative risk reduction in other populations (10%), but is much smaller than that suggested in the epidemiological study above. Both the study above and the meta-analysis found relatively greater effect in men, suggesting possible benefit from targeted use.]