Cigarette Smoking
Passive Smoking
Peripheral Vascular Disease
Stroke
Fetal Development
Lung Disease
Women and Smoking
Tobacco Addiction

[What is a Stroke?] [Dfferent Types of Strokes] [Risk Factors for Cerebrovascular Disease]
[Transient Ischemic Attacks] [Subarachnoid Hemorrhage] [Smoking Cessation] [Oral Contraceptives]

 Even though the mortality or death rate from strokes is declining in the United states, it is still a public health disease of the first order.  Strokes are responsible for 9 percent of all deaths in the United States, and represent the third leading cause of death behind only heart disease and cancer.  There are approximately 500,000 new strokes each year, resulting in 200,000 death (1).  The chances of suffering a stroke before the age of 70 is 5 percent according to to the Framingham Study, and the chance of getting a stroke doubles every decade after the age of 45.  Indeed, 20 percent of strokes in men occur prior to the age of 65, meaning it frequently occurs during the most productive period in a man's life.

What is a Stroke?

 The word "stroke" or "cerebrovascular accident" refers to a group of diseases that have in common a reduced blood supply to a portion of the brain.  This reduction in blood supply may have varying symptoms depending upon the degree of reduction (total obstruction or just a mild reduction), amount of blood that can reach the endangered region of the brain from other sources (call "collaterals"), and the part of the brain that is in jeopardy.  TIA's, or "transient ischemic attacks" represent a sub-critical reduction in blood supply to a brain region which will result in mild episodes that last for short periods of time.  These symptoms might be dizziness, numbness in an arm or a leg, or blurring of vision among others.  The importance of TIA's is that they indicate a dangerous reduction of blood supply to a portion of the brain has occurred, and that there is a very real and present danger of a full-fledged stroke. The exact number of strokes which are preceded by TIA's has been estimated in several studies from between 3 percent to 75 percent (x).  More importantly, there is about a 36 percent incidence over a 45 month period of progression on to a stroke in patients who have a history of TIA's (x).  Therefore, it is incumbent upon the patient to recognize that these symptoms are not just a part of "getting older" and to recognize them for being something potentially very dangerous, and important for the physician to recognize their true meaning and to institute preventative action.

 Unfortunately, however, the preventative action that a physician has to offer subjects with these warning episodes is very from perfect.  Basically, the treatment consists of anticoagulants or blood thinners to keep the already disease vessels from getting more diseased.  These measures will reduce the incidence of progression to a stroke, but will not reduce the chance to zero.  Surgery is another option, and can in some patients remove an isolated plaque or ulceration from a vessel.  Unfortunately, however, surgery is not the preferred option for most patients since the disease process is usually not confined to a single region of a single vessel but rather is much more diffuse.  Also, sometimes the diseased vessels are deep within the brain and cannot readily be removed.  Sometimes,. these patients are rather elderly and not in very good general medical condition such that surgery must be approached very cautiously, and may even serve to precipitate the stroke that the surgery was trying to prevent.  So the options are not very good and essentially consist of doing nothing, drug therapy which is certainly not perfect, or surgery which is contraindicated and far too dangerous for most subjects.

 Certainly, the most important type of therapy for most patients with TIA's, however, is to stop smoking.  For all the reasons we have previously listed, smoking will only serve to accelerate the atherosclerotic process despite all the drug therapy and surgery possible.  Even if surgery were possible, and it was successful in removing an atherosclerotic lesion in a part of the patient's brain, smoking will only serve to accelerate the process in another portion of the vascular system and start the process moving all over again.  Also, since smoking vastly increases the amount of carbon monoxide in a patient's blood thereby decreasing the amount of oxygen it can carry, a stroke which does happen may have a worse outcome with more severe neurological damage than would otherwise have occurred.

 Strokes are the third most common cause of death in the United States, but most people do not die from the stroke directly, but rather from the complications from that stroke, such as pneumonia, infection, and heart disease.  While I do not know of any studies, it makes logical sense that patients who have suffered from a recent stroke will do better if their lungs and heart are not already damaged by the ravages suffered from  decades of smoking.

Different Types of Strokes

 There are several different ways that strokes can be initiated, all with the same symptoms and are generally indistinguishable from each other on clinical grounds only.  The major types of stroke area;

 a. Atheroma-a fatty lesion on the inside part of a vessel wall which decreases blood flow through that vessel.  This is probably the most common type of stroke, and is certainly made worse by smoking.
 b. Thrombosis-a clot that forms on the inside of a vessel wall, generally in a region where blood flow is decreased, such as near an atheroma.
 c. Embolus-a thrombus that is carried by the blood flow into the arteries supplying the brain.  When the thrombus is carried into arteries that are so small that the thrombus cannot be carried on any further, then the blood vessel is obstructed.
 .d. Hemorrhage-bleeding into the brain may occur producing destruction of an area of the brain.  The bleeding often happens when a portion of a vessel wall breaks apart, most commonly caused by an aneurysm.  Aneurysms can be congenital in origin (present from birth), and can certainly be made worse with hypertension.

[Hypertension][Blood Cholesterol][Glucose][Cardiac Disease][Cigarette Smoking]

 The five major risk factors for producing cardiovascular disease (systolic blood pressure, serum cholesterol, diabetes, cigarette smoking, and EKG evidence of heart disease) are studied with respect to strokes, there is a predictive ability than with coronary heart disease.  The most important factors for predicting which people will develop strokes are hypertension and EKG evidence of heart disease.  Cigarette smoking turns out to be more predictive for heart disease than for strokes, but is still very important in predicting risk for strokes in young people

.Hypertension

 When a physician tells you your blood pressure, he gives you two numbers, such as 120 over 80.  These two numbers represent the systolic (or higher number) and the diastolic (lower number) blood pressure, and generally are reflective of different physiologic properties of the cardiovascular system.  The most important number in predicting which patients will develop strokes is the higher number, or the systolic blood pressure.  As we have said previously, hypertension turns out to be very important in predicting patients at risk for strokes.  In fact, 50 to 60 percent of strokes will happen in the 20 percent of the population with hypertension.  Hypertension predisposes to strokes in both sexes and at all ages, and even mild elevations of the blood pressure will double the risk for stroke.  Many elderly patients have isolated systolic hypertension (with normal diastolic pressures) and are frequently not treated for this by their physician due to lack of recognition of its importance, and the greater incidence of side-effects of anti-hypertensive medication in the elderly population.

 As we have previously discussed, cigarette smoking is important for many reasons in the formation of cardiovascular disease.  One of these ways is its effect on blood pressure.  While patients as a whole who smoke do not have a greater incidence of hypertension, those who do acquire hypertension have a greater chance of getting severe disease.  Thus, it is not too surprising that smoking cigarettes will increase the chances of getting strokes from the standpoint of worsening hypertension.

Blood Cholesterol
 Blood fats and cholesterol, so very important in the pathogenesis of coronary heart disease, are not nearly as important in the production of cerebrovascular disease and strokes.  Neither cholesterol nor triglycerides, the major blood fats implicated in coronary artery disease, are predictive for strokes past the age of 55, the time of maximal number of strokes in the population.

Glucose

 Strokes from atherothrombosis is three times more common in diabetics than in the normal population.  Additionally, in contrast to coronary artery disease, the impact of diabetes does not diminish with advancing age and is the same for men and women (2).

Cardiac Disease

 Even if symptomatic, certain cardiac diseases will predispose to the development of strokes.  Hypertension, as we have said before, is a very powerful risk factor for strokes, but so is an abnormal EKG showing enlargement of the heart.  Additionally, some forms of heart disease can greatly contribute to the incidence of strokes in some patients.

 The heart has four valves; pulmonic, tricuspid, aortic, and mitral.   Atrial fibrillation is an abnormal beating or rhythm of the heart that is very irregular and can be very fast.  Since it does not involve the ventricles directly (like ventricular fibrillation which is deadly), atrial fibrillation usually is not life threatening and indeed is fairly common.  However, when the atria beat irregularly, blood flow through certain parts of them becomes stagnant, and this is where blood clots can form.  These blood clots in the atria are like time bombs, because they can become dislodged and float from the atria into the ventricles, and from there to the brain where a stroke can result.  One of the commoner causes of atrial fibrillation is disease of the mitral valves called mitral stenosis.  Mitral stenosis is a thickening and calcification of the valves partially occluding it so that less flood can flow through.  When this happens, pressure upstream from the mtral valves increases, and this is reflected by an enlargement of the left atrium initiating fibrillation.

Cigarette Smoking

 There is no doubt whatsoever that smoking will increase the incidence of strokes, but the association is not as strong as between cigarette smoking and heart disease.  Evidence suggests that smoking is more strongly associated with premature (i.e., younger than 55 years old) strokes than strokes in the elderly population (where it is more common).  Additionally, smoking is associated with non-fatal strokes rather than fatal strokes for unknown reasons.

 After extensive follow-up of 293,000 United States veterans, Rogot and Murray (3) reported that there were excess stroke deaths associated with cigarette smoking, and that the relative risk of dying from a stroke in smokers was approximately 1.47 during 16 years of follow-up.  Kahn (4) followed smokers for 8.5 years and also found that stroke mortality was 1.4 times greater in smokers than in non-smokers.  However, the mortality ratio for strokes was not excessively increased in pipe or cigar smokers, being 1.07 and 0.99 respectively (3).  In another study comparing the incidence of strokes among the Japanese population in Japan, Hawaii, and California, analyses have so far revealed positive correlations between strokes and increased blood pressure, electrocardiographic indication of heart disease, and cigarette smoking for all ages (5).

 However, there are many investigations which either do not show an association between strokes and cigarettes, or only show such an relation in certain restricted populations.  The Framingham study, for example, showed that after 24 years olf following, there was no statistically significant relationship between the incidence of atherothrombotic strokes and cigarette smoking among males.  However, the stroke incidence was lower in nonsmoking males between the ages of 45 and 55, but no clear dose-response relationship was appreciated (6).  Paffenbarger et al. (7) also showed no relationship between cigarette smoking and stroke after 22 years of follow-up of 3686 longshoremen.

 Another study by Paffenbarger and Wing (8) was a prospective evaluation of chronic diseases among male former students at Harvard University.  They appreciated a slight excess incidence of nonfatal stroke among those who have smoked during their college years.  Another study performed in a similar was was a Canadian retrospective study (9) which noted a 2.4 times increased risk of having a stroke among smokers compared to nonsmokers.  However, the results obtained from these types of studies must be evaluated with some caution as smoking histories were obtained from existing school records which might not be complete, and smoking information was not collected in a standardized manner.

 An additional large study was performed by Hammond and Horn (10) who evaluated the relationship between smoking cigarettes and disease among 187,783 white men 50 to 69 years old, followed from May 1952 through October, 1955.  There were 11,870 deaths during this period, and 1,050 were listed as being from cerebrovascular disease.  There was a statistically significant excess mortality ratio of 1.03 among smokers compared to nonsmokers appreciated in this study.  Also, there was found a dose-response relationship such that those who smoked more cigarettes suffered from a greater incidence of strokes.

 Even through the results are somewhat contradictory, there does seem to be a slight increase in stroke death rate among those who smoke cigarettes in the elderly population.  However, the evidence is much more convincing in the younger population where strokes are much rarer.  Koch et al. (11) reported in 1977 upon 100 male stroke patients aged 40 to 69 and found an 11.2 times greater risk of having a stroke for smokers of more than one pack per day.  Another study performed by MacKay and Nias in England reported in 1979 upon 56 male and 34 female patients under 66 years of age with strokes and again found a significantly greater incidence of smoking among stroke patients than among their matched controls.

 While the incidence of strokes among the younger population undoubtedly is quite small, the impact for that patient and their family will be quite large.  Indeed, it may be one thing for a very elderly, sick patient to suffer from a stroke, and quite another for a young, otherwise vibrant patient in the middle of their productive life with a growing family to be similarly incapacitated.

Transient Ischemic Attacks (TIAs)

 TIAs are transient neurological symptoms that generally last for several minutes but not longer (by definition) than 24 hours.  They are usually due to atherothrombotic lesions of the arteries that supply portions of the brain.  Additionally, they may be due to a sudden fall in blood pressure, emboli dislodged from the vessel (or left atrium as described above with atrial fibrillation), changes in cardiac rhythm that can reduce the blood pressure, or a severe reduction in blood oxygen levels.  The significance of TIAs is that they are possibly a harbinger of serious things to come, more specifically a full-fledged stroke.  In one study, there was a 36 percent incidence of strokes following TIAs in a 45 month period of observation (x).

 There is some evidence linking the incidence of TIAs with cigarette smoking, although the data is not overwhelming.  Rhoads et al. reported in 1980 upon Japanese men living in Hawaii.  In a six-year follow-up period of 7895 men aged 45 to 68, prior cigarette smoking was associated with TIA, even when other risk factors were taken into consideration.  However, these findings were not substantiated in an earlier study by Ostfeld in 1973  who studied the risk of stroke in an elderly population (12).

Subarachnoid Hemorrhage

 The brain is surrounded by three layers of tissue which helps to protect the brain from damage.  Two of these layers, the pia mater and the arachnoid, are on either side of a space called the subarachnoid space. a The significance of this space is that this is an area that bleeding can occur after a brain hemorrhage, producing a subarachnoid hemorrhage.  As might be expected, this bleeding is often a very serious medical emergency, and can lead to serious, permanent sequellae, or even death.

 A retrospective study performed by Bell and Symon in 1979 show a correlation between subarachnoid hemorrhages and cigarette smoking.  Petitti et al. also reported in 1978 upon this association, and disclosed a 5.7 times greater risk of subarachnoid hemorrhage in smokers compared with nonsmokers.  In a 6.5 year follow-up of these 16,759 white middle-class patients aged 18 to 54, there was a five to seven times greater risk of subarachnoid hemorrhage, and a 4.8 times greater risk for other types of strokes compared with nonsmokers.

Smoking Cessation

 Since cigarette smoking seems to be associated with strokes, there is reason to believe that smoking cessation should reduce that risk.  Indeed, this has been shown to be the case, although the studies so far performed are not the controlled, clinical investigations that one would like to see.

 In one study, there was a 16 year follow-up of 293,000 insured American veterans (3) that investigated the mortality rates for different diseases in relation to smoking status.  For stroke, the mortality rate for the ex-smoker returned to that of a non-smoker one year after smoking cessation.  Additionally, Koch et al. (11) demonstrated that the increased risk of strokes in young people who were smokers was not detectable after one year of smoking cessation.

Oral Contraceptives

 The use of oral contraceptives and smoking cigarettes is a potent combination for stroke production in young women.  The data is not as strong as one would like due to the low incidence of strokes in the young female population generally.  However, there are several good retrospective studies which demonstrate a definitely increased risk when these two activities are undertaken.

 In 1969, the Walnut Creek Contraceptive Drug Study began a long term study on the effects of oral contraceptives on women's health.  After 6.5 years of follow-up of 15,260 women, Petitti and Wingerd (13) demonstrated significantly increased risk for strokes in these women.  Specifically, they showed a 6.5 and 7.6 times increased risk for subarachnaoid hemorrhage and thromboembolism respectively.  Significantly, the risk of subarachnoid hemorrhage for women show both smoked and used oral contraceptives was 21.9 times that of nonsmokers who did not use oral contraceptives.

 In another study, Stadel (14,15) demonstrated that the use of oral contraceptives multiplies the risk or age and other factors in the development of heart attacks and strokes.  Similar data was also presented by the Collaborative Group for the Study of Stroke in Young Women (16) who showed that cigarette smoking and the use of oral contraceptives were each independent risk factors for subarachnoid hemorrhage.  When a heavy smoker also took oral contraceptives, the risk for a subarachnoid hemorrhage increased to 6.1 to 7.6 times that of nonsmokers.

 These data strongly suggest that the concomitant use of oral contraceptives and cigarette smoking significantly increase the risk of certain types of strokes in these young women when compared to those women who do not smoke.