Aspirin in type 2 diabetes: is there any evidence base?

While I (MW) was observing general practitioner consultations as a medical student, a 46 year old woman with type 2 diabetes presented for prescriptions. Because this is a common presentation, I thought this was one consultation that I should tune into. The patient’s diabetes was well controlled by diet and lifestyle alone. Her most recent glycated haemoglobin value was 6.1%. Hypercholesterolaemia (total cholesterol/high density lipoprotein cholesterol 4.2) and hypertension (blood pressure 125/80 mm Hg) were effectively managed with drugs. She was a regular smoker, which gave her an absolute cardiovascular risk of 5-10% (New Zealand cardiovascular risk calculator; www.nzgg.org.nz/guidelines/0035/CVD_Risk_Chart.pdf) over five years. However, one of the drugs she was taking didn’t make sense to me, so I asked my supervisor why someone with well controlled diabetes who was otherwise healthy should be on aspirin. “It’s routine to give someone with type 2 diabetes aspirin,” he assured me. I must have looked unconvinced because his initial confidence faltered and gave way to a slightly uncertain frown. We wondered, “What is the evidence base behind routinely prescribing aspirin in type 2 diabetes?”