Effects of Smoking

Effects of Smoking

1. Death

· Life expectancy of smokers is shorter than that of non-smokers – 40% of heavy smokers die between 35 and 65 compared with 15% in non-smokers.

· By a large margin, biggest preventable cause of death.

· Responsible for 1 in 10 adult deaths.

2. Cancer

· Especially lung and upper respiratory but also oesophagus, pancreas and bladder.

· Smoking 20 cigarettes a day increases risk 10-fold.

· 90% of lung cancers caused by smoking.

· Tar is causative.

3. Coronary heart disease and peripheral vascular diseases

· Mortality in men aged 55-64 from coronary thrombosis 60% greater in men who smoke 20 cigarettes a day than non-smokers.

· Stroke, intermittent claudication, diabetic gangrene, etc. also strongly smoking-related.

· Nicotine mainly responsible.

· Another factor may be carbon monoxide.

4. Chronic obstructive pulmonary disease (chronic bronchitis and emphysema)

· Much more common in smokers than in non-smokers.

· Probably due to tar and other irritants.

5. Teratogenicity and harmful effects in pregnancy

· Particularly during latter half of pregnancy, significant decrease in birth weight and perinatal mortality.

· Increased incidence of spontaneous abortion, premature delivery and placenta praevia.

· Nicotine in breast milk may cause tachycardia in infant.

· Nicotine responsible for retarded foetal development.

6. Dependence and withdrawal

7. ?Protective effects

· Parkinson’s disease twice as common in non-smokers as in smokers.

· Reduced symptoms from inflammatory bowel disease.

Agents of harm

1. Tar and irritants

· Carcinogenic hydrocarbons and tumour promoters.

· Various irritants responsible for bronchitis and emphysema.

2. Nicotine

· Complex CNS effects.

o Activation and desensitisation of cortex and hippocampus (cognitive function) as well as ventral tegmental area (dopaminergic neurons).

o Inhibition of spinal reflexes leading to skeletal muscle relaxation.

· Peripheral effects

o Stimulation of autonomic ganglia causing tachycardia, increased cardiac output, increased arterial pressure, reduction of gastrointestinal motility and sweating.

o Secretion of adrenaline and noradrenaline from adrenal medulla contributes to cardiovascular effects.

o Release of antidiuretic hormone from posterior pituitary causing decreased urine flow.

o Increased plasma concentration of free fatty acids.

3. Carbon monoxide

· Higher affinity than oxygen for haemoglobin.

· Contributes to increased incidence of heart and vascular disease.

4. Increased oxidative stress

· May be responsible for atherogenesis and chronic obstructive pulmonary disease.

Resource: Rang and Dale's Pharmacology