Statins and Stroke
Statin medications reduce the risk of stroke in people with vascular disease. They have not been shown to reduce the risk of stroke without atherosclerosis. For those with plaque on their blood vessels, statins cause a decline in incidences of ischemic stroke, but probably not those of hemorrhagic stroke. Ischemic stroke is when an obstruction in the artery cuts blood flow to part of the brain, resulting in death or damage to parts or elements of the brain. An obstruction in the artery is more likely if there is buildup of plaque on the arterial walls, such as happens in cerebral arterial disease.
Hemorrhagic stroke occurs when a weakened blood vessel ruptures in the head, allowing blood to flow outside it’s normal channel and likewise causing death or disruption of neurons. Most hemorrhagic stroke occurs in people with high blood pressure.
The large majority of strokes are ischemic strokes, and high cholesterol contributes to the risk for those strokes. This is why statins are used for both primary and secondary prevention – i.e. to prevent a first stroke and a follow-on stroke.
The medicines have a less of a preventative effect in patients without diagnosed artery disease. Further, even after people have had a stroke or transitory ischemic attack, using statins reduces the risk of a second stroke. This may be due to statins' biochemical action that aid in brain recovery after a stroke.
Epidemiological studies have shown that statins help elderly people as well as younger stroke patients in recovery. Two European studies show statins reduce the risk of venous thromboembolism. It is also worth distinguishing between ischemic stroke and hemorrhagic stroke. Ischemia is when the brain's blood supply is cut off by thrombosis or embolism, while hemorrages are when tissue ruptures to release blood. Statins decrease the risk of ischemic stroke, but there is some indication that they increase the risk of hemorrhagic stroke.
A meta-analysis found that a reduction in serum cholesterol level of only 18 mg/dl reduces the chance of stroke by 20%. The risk of non-fatal stroke fell more than the risk of fatal stroke.
Given that the etiology of heart disease and strokes are similar, it is not surprising that statins would be beneficial for strokes, although it should be noted that epidemiological and observational studies have not shown a definitive association between cholesterol levels and stroke. Researchers suspect that statins play a part beyond their cholesterol-lowering function in stroke prevention. This may be one of the pleiotropic effects of statins.
Peripheral Arterial Disease
This disease is caused by cholesterol plaques on the blood vessels in parts of the body outside and chest, neck, and head. The classic example is disease in the legs.
It’s basically atherosclerosis in the rest of the body. Like other atherosclerosis it is caused by high cholesterol levels in the bloodstream, and statins can reduce risk. Such amorphous descriptions of disease as "poor circulation", "vascular disease", and "claudication" often turn out to be peripheral arterial disease (PAD). Other names include peripheral vascular disease and atherosclerotic peripheral arterial disease. The patient often notices leg cramps or weakness, especially during exercise. Sometimes sores that won’t easily heal are a sign, and some people get shiny skin near affected areas.
Why is peripheral arterial disease bad? Blocked or narrowed blood vessels can result in pain and weakness in the affected parts of the body. If bad enough and left untreated, gangrene can set in.
Peripheral arterial disease also increases risk for heart attack, coronary heart disease, and stroke. When a patient has PAD he or she is always given a close examination of the entire cardiovascular system. PAD patients with high LDL-C are often put on a statin medication. If the LDL-C level is low, niacin and/or fibrates are employed.
The goals of the treatment of PAD are to
- reduce pain,
- slow the progression of atherosclerosis,
- improve the macro- and microcirculation,
- reduce the risk of blood clots that will break off and cause cardiovascular and cerebrovascular events
Statins have not been shown to improve treadmill times in patients with claudication in the legs, but they have been shown to help with symptoms.
Venous Thrombus and Pulmonary Embolism
Blood clots can form in the body due to many factors. If a clot travels in the blood it is called a thromboembolism and it if gets to the pulmonary arteries that supply blood to the lungs, the result is a pulmonary embolism. Pulmonary embolisms are dangerous and about one in three times results in death.
While statins have been proven to reduce the risk of cardiovascular disease, the evidence for their being of any use in preventing embolisms is not nearly as strong. While there might be an association between serum lipid levels and venous thromboembolism, nobody thinks cholesterol directly causes blood clots. And experts feel that if statins do influence embolism occurrence, it is through the so-called pleiotropic effects. The lowering of cholesterol levels is incidental, or at least less important. The statins reduce circulatory system inflammation and have antioxidant effects – in particular they may help prevent the breakdown of proteins that stop clots from forming.
A Danish study of patients who took statins after being hospitalized for a venous thromboembolism for statins reduced the risk of a follow-on embolism. This is a secondary prevention for high risk patients.
A review by some French scientists conceded "several observational cohort and case-control studies appear to show that statins reduce the incidence of venous thromboembolism by about 30%" but concluded the science in this area was not strong enough to support recommendations of statins for primary or secondary prevention.