Smoking and Stroke

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What is a Stroke?

A stroke is a life-threatening condition that happens when part of your brain does not have enough blood flow. This most commonly happens because of a blocked artery (ischemic stroke) or bleeding in your brain (Haemorrhagic stroke). This will result in tissue damage due to a lack of oxygen.

According to WHO, Stroke is defined as a clinical syndrome consisting of rapidly developing clinical signs of focal disturbance of cerebral function lasting more than 24 hours or leading to death with no apparent cause other than vascular origin.

How common is Stroke?

Stroke is the second commonest cause of death in India. About 1,85,000 strokes occur every year in India with nearly one stroke every 40 seconds and one stroke death every 4 minutes.

The average annual incidence rate (IR) of stroke in India is 145 per 100,000 population. The overall incidence ranges from 105 to 152 per 100,000 population. The crude prevalence of stroke ranges from 44.29 to 559/100,000 persons in different parts of the country during the past decade.

How does smoking causes Stroke?

The cigarette smoke contains thousands of harmful chemicals such as:

• Formaldehyde: Can cause nasal cancer, damage the digestive system, skin, and lungs
• Nicotine: Causes physical and psychological dependency
• Benzene: A toxic compound and known cancer causing substance in humans
• Carbon monoxide: A poisonous gas that takes the place of oxygen in the blood
• Arsenic: Associated with toxicities related to vasoconstriction and other cardiovascular effects, lung cancers, dermal cancers, and dermal sensitization
• Hydrogen cyanide: Interferes with the body's use of oxygen which are transferred from your lungs into your bloodstream.

These chemicals change and damage cells and affect your circulatory system and increase your risk of stroke. Smoking can affect your body’s cholesterol levels, it reduces the levels of HDL (Good cholesterol) and increases  the levels of LDL (Bad cholesterol). Higher levels of LDL cholesterol increases the risk of stroke.

Carbon monoxide reduces the amount of oxygen in your blood while nicotine makes your heart beat faster, raising your blood pressure. Half of all strokes are linked to elevated blood pressure.

The chemicals in tobacco smoke also make your blood more prone to clotting. Together these effects of smoking increase your risk of developing atherosclerosis. People with atherosclerosis have narrower, less fexible arteries which reduce the blood fow, contribute to higher blood pressure and increase the likelihood of blood clots. Blood clots that travel to the brain stop blood and cause brain cells to die.

Nirandeep Rehill, Charles R. Beck et al (2006) conducted a study entitled “The effect of chronic tobacco smoking on arterial stiffness” and concluded that Chronic tobacco smoking is associated with endothelial dysfunction and increased Augmentation Index in subjects of a wide age range free from additional cardiovascular risk factors, which is partially reversible after 4 weeks of smoking cessation.

Does passive smoking can increase the risk of stroke?

Yes, passive smoking can increase the risk of stroke has been reported in many studies. Passive smoking can lead to carotid atherosclerosis, and the levels of homocysteine, fibrinogen, and oxidized low-density lipoprotein cholesterol can also be elevated by smoking.

mechanisms by which primary and environmental tobacco smoke exposure can increase the risk of stroke and heart disease are numerous and include carboxyhemoglobinemia, increased platelet aggregability, increased fibrinogen levels, reduced HDL-cholesterol, and direct toxic effects of compounds such as 1,3-butadiene, a vapor phase constituent of environmental tobacco smoke that has been shown to accelerate atherosclerosis. Environmental tobacco smoke exposure has also been linked to the progression of atherosclerosis.

These studies have convincingly shown that environmental (second-hand) smoke increases the risk of stroke even in nonsmokers. Bonita et al. found that Passive smoking as well as active smoking increases the risk of acute stroke.

"Low cigarette consumption and risk of coronary heart disease and stroke: meta-analysis of 141 cohort studies in 55 study reports" by A hackshaw concluded that Smoking only about one cigarette per day carries a risk of developing coronary heart disease and stroke much greater than expected: around half that for people who smoke 20 per day. No safe level of smoking exists for cardiovascular disease. Smokers should aim to quit instead of cutting down to significantly reduce their risk of these two common major disorders.

Benefits After Quitting

When a person stops smoking, their body begins to feel the benefits quickly,these include:

• Within 20 min blood pressure drops to the level it was before the last cigarette
• Within 8 hours carbon monoxide levels in the blood return to normal
• Within 24 hours the chance of a heart attack decreases
• Within 2 weeks to 3 months circulation improves and lung function increases
• Within 1–2 months smoking-related stroke risk due to hypercoagulability normalizes to that of nonsmokers
• Within 1–9 months lungs regain normal ciliary function, reducing infection risk
• At 1 year the risk of heart disease is cut in half
• At 5 years stroke risk is reduced to that of a nonsmoker in most cases
• By 10 years the risk of lung cancer is approximately half that of a smoker. The risks for cancers of the mouth, throat, esophagus, bladder, kidney and pancreas also decrease
• By 15 years the risk of heart disease is that of a nonsmoker