should we??. aspirin is useful! it is widely used in secondary prevention it reduces the yearly risk...
TRANSCRIPT
Should we??
Aspirin is useful!It is widely used in secondary preventionIt reduces the yearly risk of vascular events
by about a quarterThis corresponds to an absolute reduction of
about 10-20/1000 non fatal events...and a smaller, but definite, reduction in
deathTherefore the increase in major bleeds is a
risk worth taking
SIGNAcknowledges that there is some controversy
about the use of aspirin in Primary Prevention of Cardiovascular disease
It reduces risk of MI by 30%......but increases risk of haemorrhagic stroke
by 40%......and major GI bleeds by 70%All cause mortality not affected
SIGN...So, do you wait for a first event? It could be a
fatal one!
SIGN conclude that the “cut off” where the risk is worth it...
...is a calculated cardiovascular risk of > 20%
SIGNIn doing so, SIGN, like other guidelines tends
to assume:1. That the risk of bleeding remains constant
irrespective of the risk of cardiovascular disease
2. ...or that it depends on age alone
But is that justified?
Today...BMJ 2005 330:1440-41
“Aspirin for everyone older than 50?”
Antithrombotic Trialists’ CollaborationMay 2009, Lancet
The authors recognised that existing metanalysis trials didn’t involve details about the individuals in the trial
Therefore, couldn’t look at important separate groups eg. Elderly, men, women, those at “high risk”...
Aims• To assess the incidence of serious vascular
events and major bleeds in primary and secondary prevention trials, comparing aspirin with controls
• To further analyse the primary prevention trials by looking at individual participant data to compare the benefits/risks of aspirin in prognostically important groups eg. Male v Female, old people...
MethodLooked at primary and secondary trials to
provide a comparison
Analysed individual data
Six primary prevention trials
16 Secondary prevention trials
Results
Whether Aspirin is used in primary or secondary prevention, the proportion of reduction in major coronary events or in stroke is about the same.
Because patients in the primary prevention group are less at risk anyway, the absolute risk is therefore much smaller
Looking more closely...
Primary prevention trials showed 1671 serious vascular events in 330,000 aspirin-person-years in the aspirin group
Vs1883 events in 330,000 person years in the
control group
Looking more closelyIn primary prevention, aspirin reduces the
rate of serious vascular events by 12% (0.51% Vs 0.57% events per yr)
This is largely due to the fall in MIs
Ischaemic strokes largely unchanged
Overall vascular mortality is unchanged
Even more...• This risk reduction of events didn’t alter even if
you were...• Young• Old• Fat• Thin• Male• Female• Smoker• Diabetic• Ugly (Just joking)• Or “cardiovascular risk of > 20%”
And to rub more salt into the wound...
Nowadays, anyone who is “at risk” is on1.Statins (which halve the risk on their own)2.Antihypertensives...which further reduces a patients absolute
risk of events......without a risk of bleeding...
So...Therefore, adding in aspirin will only give an
even smaller reduction in the risk of events
But the bleeding risk will probably remain the same!
Actually, this paper suggests that there are risk factors for bleeds: Diabetes, Hypertension...
Caveats• We might be wrong, because the papers
might be wrong (ie have underestimated the risk reduction of vascular events)
• There might still be a particular group for whom aspirin is of net benefit. Eg diabetics without vascular disease
• The vast majority of the participants where at low risk so the data might not be reliable for higher risk groups
Nailing your colours to the mast! (Summary)In primary prevention, aspirin is of
uncertain net value as the reduction in occlusive events needs to be weighed against the increase in major bleeds.
This is compounded when we treat with other risk-lowering drugs
So....?SIGN haven’t yet changed the guidelines
What do we do in the meantime?
Would you take Aspirin for Primary Prevention?