UK doctors still undertreating major risk factor for stroke
Despite significant improvements in stroke prevention over the past decade, and a fall in incidence and deaths, UK doctors are still undertreating one of the major risk factors - atrial fibrillation - reveals research published in BMJ Open.
Atrial fibrillation, or AF for short, describes abnormal heart rhythms. Its treatment has been prioritised in the NHS in a bid to cut preventable deaths and disability from stroke.
The researchers base their findings on an analysis of stroke data drawn from the General Practice Research Database (GPRD) for the period 1999 to 2008. The GPRD contains long term anonymised data on three million UK primary care patients.
More than 32,000 adults had a stroke, one in seven (15%) of which were fatal, during the study period.
Women were more likely to die of a stroke than men, even after taking account of age. The average age for a first stroke was 77 years for women and 71 years for men.
The figures showed significant improvements both in the number of new cases of stroke and in subsequent survival.
The prevalence of stroke rose by 12.5%, but the number of new cases fell by almost a third (30%) over the decade - from 1.48 per 1,000 person years in 1999 to 1.04 in 2008.
Risk Factors for Ischemic Stroke
Age, gender, race, ethnicity, and heredity have been identified as markers of risk for stroke. Although these factors cannot be modified, their presence helps identify those at greatest risk, enabling vigorous treatment of those risk factors that can be modifed.
Age is the single most important risk factor for stroke. For each successive 10 years after age 55, the stroke rate more than doubles in both men and women. Stroke incidence rates are 1.25 times greater in men, but because women tend to live longer than men, more women than men die of stroke each year.
An increased incidence of stroke in families has long been noted. Potential reasons are a genetic tendency for stroke, a genetic determination of other stroke risk factors, and a common familial exposure to environmental or lifestyle risks. Earlier studies suggested an increased risk for men whose mothers died of stroke and women who had a family history of stroke. In the Framingham Study an offspring analysis revealed that both paternal and maternal histories were associated with an increased risk of stroke.
Among those aged 80 and over, who are at the highest risk of stroke, the fall was even greater, at 42%.
The rate of deaths within 56 days of a first stroke almost halved, falling from one in five (21%) in 1999 to nearly one in 10 (12%) in 2008.
It has long been known that patients who have chronic, persistent, or frequent episodes of atrial fibrillation have an increased risk of stroke.
The increased risk comes from the fact that, during atrial fibrillation, the heart’s atria are not squeezing effectively. Consequently, the blood tends to “pool” in the atria - and whenever blood flow is disrupted, blood clotting can occur. Clots that form in the atria can break loose eventually, and if the clots travel through the arteries to the brain, a stroke results.
For patients who have atrial fibrillation, the risk of stroke depends on their age, and on other medical conditions they may have. Because the risk of stroke depends on several factors in addition to the presence of atrial fibrillation, deciding whether anticoagulation with Coumadin (a blood thinner) is warranted has been a relatively complicated decision.
These improvements were paralleled by a consistent rise in prescriptions for preventive drugs, particularly those used to lower cholesterol and high blood pressure, both of which are risk factors for stroke.
But doctors undertreated patients with atrial fibrillation, the findings showed.
Around one in 10 patients had been diagnosed with AF before their first stroke, and this group were at significantly higher risk of death from stroke than those who did not have AF.
But only one in four of all those with AF were prescribed preventive anticoagulant (blood thinning) treatment, with no sign that more serious AF was being targeted.
Women were significantly more likely to have serious AF than men, but they were less likely to be given anticoagulant therapy. This was prescribed for 29% of men with AF, but only 22% of women.
Both men and women with AF were more likely to be prescribed anticoagulants after a first stroke, but while this rose from 29% to 48% of men, it only rose from 22% to 35% of women.
Depending on the age of a person, and the specific cause of chronic atrial fibrillation, the incidence of stroke in people with this disorder can range from 5 to 17-fold higher than that of people without atrial fibrillation. Most commonly, atrial fibrillation causes cardioembolic strokes - those caused by a clot that escapes from the heart and blocks a blood vessel in the brain. Blood clots are known to form whenever blood remains static for prolonged periods of time, or as a result of turbulent blood flow, both of which are likely to occur during the erratic and disorganized heart beat of atrial fibrillation.
Sources:
Barker Fiebach, and Zieve, Principles of Ambulatory Medicine, Seventh Edition, Baltimore, Williams and Wilkins.
Bradley G Walter, Daroff B Robert, Fenichel M Gerald, Jancovic, Joseph Neurology in clinical practice, principles of diagnosis and management. Fourth Edition, Philadelphia, Elsevier, 2004.
The authors conclude that primary care doctors are tackling the risk factors for stroke much more effectively. “However, there is a clear suggestion that risk stratification is not yet optimal, particularly in relation to patients with AF,” they write.
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BMJ-British Medical Journal