Date Published: 1 May 2007
Caution urged about daily aspirin for healthy over-75s (Oxford Uni)
An Oxford University study has suggested that the number of people over 75 having certain types of stroke has increased in the last 25 years due to the use of ‘blood-thinning’ drugs, including aspirin.
The researchers point out, however, that in people at definite risk, such as those who have had a previous heart attack or stroke, blood-thinning drugs like aspirin are undoubtedly of overall benefit.
Strokes fall into two types: haemorrhagic, where there is bleeding in the brain, and ischaemic, where there is a blockage in the blood supply to the brain due to a blood clot.
Antithrombotic or ‘blood-thinning’ drugs, such as aspirin, reduce the risk of ischaemic strokes by making blockages by blood clots less likely. For this reason, many healthy people take aspirin daily to prevent stroke, as well as to prevent heart attacks caused by blood clots. However, the new research highlights one of the potential risks of antithrombotic drugs: increased incidence of haemorrhagic stroke. The findings are published online today by The Lancet Neurology.
‘Antithrombotics, or clot-busting drugs, are known to prevent stroke and heart attacks in people who have vascular disease – that is, disease involving the blood vessels,’ says Professor Peter Rothwell, who led the research.
" They work because they make the blood less sticky, so less likely to clot and block blood vessels.
_ Many healthy older people also choose to take regular aspirin in the hope of preventing a disabling stroke or heart attack. However, thinning the blood has a downside: it can lead to bleeding, or haemorrhage. A haemorrhage in the brain also usually results in a disabling stroke or death. "
Professor Rothwell and colleagues at Oxford’s Department of Clinical Neurology studied data from the Oxford Community Stroke Project (1981–86) and the Oxford Vascular Study (2002–06). They investigated incidence of haemorrhagic stroke over time, for patients both above and below 75 years old, together with associated risk factors such as high blood pressure and medications.
They found that incidence of such strokes had fallen in younger age groups, largely due to a better treatment of blood pressure, but there had been a slight increase in numbers of haemorrhages in the over-75s despite much better control of blood pressure.
The explanation for this lack of a fall in incidence in the elderly appeared to be an increase in strokes associated with use of antithrombotic drugs. Whilst only four per cent of patients with haemorrhagic stroke were taking antithrombotic drugs in the 1981–86 study, this proportion had increased to 40 per cent by the 2001–06 study.
Professor Rothwell said:
" Stroke is often disabling or fatal, and despite the promise of new therapies, prevention must remain the primary goal.
_ Our findings suggest that increasing use of “blood-thinning” drugs may soon overtake poorly controlled blood pressure as the major risk factor for haemorrhagic stroke in over-75s.
_ In people at definite risk, such as those who have had a previous heart attack or stroke, antithrombotic drugs like aspirin are undoubtedly of overall benefit. However, our results show that such drugs now account for a high proportion of bleeds in the population, many in healthy elderly patients who don't have vascular disease but who take aspirin in the hope of preventing a stroke.
_ Even in this group, the benefits of aspirin could still outweigh the risks – more trials are ongoing. We just need to be cautious in advocating widespread use in healthy over-75s until we have more data on the balance of risk and benefit. "
Professor Rothwell commented that the findings show the importance of studying the older age group.
" This potential rise in the burden of haemorrhagic stroke could not have been predicted from previous studies of mortality data, which were limited to under-75s. Since at least two-thirds of haemorrhagic strokes and half of all strokes occur above 75, it is essential to include the older population in studies of stroke. "
In an accompanying comment in The Lancet Neruology, Dr Dawn Kleindorfer, director of the Stroke Prevention Programme Greater Cincinnati/Northern Kentucky, USA, said:
" Stabilisation of the incidence of stroke, especially the high morbidity and mortality associated subtybe of intracerebral haemorrhagic stroke, is not good news. As our population continues to age, the actual number of events will continue to increase, and overwhelm our already overburdened healthcare systems.
_ We need to find new and better ways to prevent stroke and change behaviour of patients and physicians so that this stable incidence trend does not continue. "
Source: Oxford University (England, UK).