Chronic smoking, the prolonged use of tobacco products, is a significant global public health challenge. This behavior, involving drawing smoke from burning tobacco into the lungs, contributes to a substantial burden of disease and premature death worldwide.
Physical Health Consequences
Chronic smoking damages nearly every organ system, accelerating the development of various diseases. The thousands of chemicals in tobacco smoke, including over 70 known carcinogens, trigger damaging cellular changes. This exposure leads to physiological impairments that accumulate over time.
Respiratory System Effects
Chronic smoking severely impacts the respiratory system. Conditions like Chronic Obstructive Pulmonary Disease (COPD), encompassing emphysema and chronic bronchitis, are primarily caused by tobacco smoke. Emphysema ruptures delicate air sacs (alveoli), reducing surface area for oxygen absorption. Chronic bronchitis involves long-term airway inflammation, causing persistent coughing and mucus. Smoke chemicals, like phenols, destroy cilia lining airways, impairing the lungs’ cleaning system and increasing infection susceptibility.
Cardiovascular System Effects
Chronic smoking increases the risk of cardiovascular diseases, including heart disease, stroke, and peripheral artery disease. Tobacco smoke chemicals, particularly oxidizing agents, damage heart muscles and blood vessels, promoting plaque buildup (atherosclerosis) on artery walls, which narrows and stiffens blood vessels. Smoking also makes blood stickier and more prone to clotting, which can block blood flow. Nicotine temporarily increases heart rate and blood pressure by stimulating the sympathetic nervous system.
Cancer Links
Beyond lung cancer, overwhelmingly caused by smoking, tobacco use links to numerous other cancers. These include cancers of the mouth, throat, esophagus, bladder, kidney, pancreas, stomach, colon, and cervix. Carcinogens in tobacco smoke induce genetic changes in cells, leading to abnormal cell growth. For instance, chemicals like benzopyrene and nitrosamines contribute to oral cancer.
Other Body System Impacts
Chronic smoking impacts many other body systems. Skin can experience premature aging, wrinkling, and psoriasis due to reduced blood flow. Nicotine hinders calcium absorption and bone-forming cell production, contributing to osteoporosis. Oral health suffers, with stained teeth, gum disease (periodontitis), bad breath, tooth decay, and tooth loss. Vision can be affected, increasing the risk of macular degeneration and cataracts, and smoking also weakens the immune system, leading to constant inflammation, reduced ability to fight infections like pneumonia and influenza, and increased likelihood of autoimmune diseases.
Brain Effects and Addiction
Chronic smoking profoundly impacts the brain. Nicotine, the primary psychoactive drug in tobacco, is highly addictive, making quitting exceptionally challenging.
Nicotine’s Mechanism of Action
Nicotine rapidly enters the bloodstream and travels to the brain, crossing the blood-brain barrier. In the brain, nicotine acts on nicotinic acetylcholine receptors (nAChRs), normally activated by acetylcholine. By mimicking acetylcholine, nicotine hijacks the brain’s reward pathway, primarily in the ventral tegmental area (VTA). This stimulates dopamine release, a neurotransmitter associated with pleasure, reinforcing repeated use.
Development of Dependence
Repeated nicotine exposure leads to neuroadaptation, where the brain adjusts to the drug’s constant presence. Over time, the brain becomes accustomed to elevated dopamine levels, requiring more nicotine for the same effect, known as tolerance. This continuous demand results in physical and psychological dependence.
Withdrawal Symptoms
When nicotine intake stops, individuals experience withdrawal symptoms. These typically begin hours after the last cigarette, peak within two days to a week, and can persist for several weeks. Common symptoms include intense cravings, irritability, anxiety, anger, difficulty concentrating, restlessness, impatience, increased appetite, headaches, and depressed mood. These symptoms contribute to relapse, making sustained abstinence difficult.
Cognitive Impact
Chronic smoking negatively affects cognitive functions. Smokers often perform poorer on neuropsychological tests than non-smokers, particularly in selective attention, alternating attention, working memory, short-term and long-term memory, processing accuracy, and executive function. Studies show faster decline in global cognition and executive function in middle-aged male smokers. This impairment stems from smoking’s damage to the brain’s blood supply, reducing oxygen delivery, and potentially altering brain structure.
Link to Mental Health
The relationship between chronic smoking and mental health disorders like anxiety, depression, and schizophrenia is complex. Individuals with mental illnesses, particularly schizophrenia, have a significantly higher prevalence of smoking compared to the general population. While smoking is often perceived as a form of self-medication to alleviate symptoms or medication side effects, evidence suggests that nicotine does not improve psychological symptoms and can even worsen underlying conditions. Quitting smoking has been shown to improve mental health, with longer periods of abstinence leading to better psychological well-being.
Impact on Specific Groups and Through Exposure
The health consequences of chronic smoking extend beyond the individual smoker, affecting vulnerable populations and those exposed to tobacco smoke in their environment.
Youth and Adolescents
Youth and adolescents are particularly susceptible to nicotine addiction due to their developing brains. The adolescent brain undergoes significant reorganization, especially in regions governing executive function, decision-making, and emotional regulation, making it more vulnerable to nicotine’s effects. Nicotine exposure during these formative years can lead to permanent physical changes in brain structures like the prefrontal cortex and ventral tegmental area, impairing attention, memory, and learning abilities. Early smoking initiation also increases the risk of developing mood disorders like anxiety and depression, and can heighten vulnerability to other substance abuse later in life.
Pregnant Individuals and Fetal Development
Smoking during pregnancy poses severe risks to both the pregnant individual and the developing fetus. Nicotine and carbon monoxide from tobacco smoke can cross the placenta, affecting multiple developing organs, including the fetal lungs, adrenal glands, and brain. Maternal smoking is a significant risk factor for premature birth, low birth weight, and an increased risk of sudden infant death syndrome (SIDS). It can disrupt brain development, particularly serotonin neuronal development, and impair the infant’s ability to respond normally to oxygen deprivation and arousal.
Elderly Individuals
Chronic smoking can accelerate age-related decline and worsen existing age-related diseases in older adults. Smokers over 75 years of age may experience a more rapid decline in memory and poorer performance on cognitive tests compared to non-smokers of similar age. Even in otherwise healthy seniors, smoking can independently contribute to cognitive decline. The long-term accumulation of smoking-related damage increases the risk of conditions like osteoporosis, vision loss from cataracts and macular degeneration, and can complicate the management of diseases such as type 2 diabetes.
Secondhand Smoke (Passive Smoking)
Secondhand smoke, also known as passive smoking, is the smoke exhaled by a smoker and the smoke from the burning end of a cigarette, cigar, or pipe. There is no safe level of exposure to secondhand smoke, and even brief exposure can cause immediate harm. Non-smokers exposed to secondhand smoke face increased risks of heart disease, stroke, and lung cancer. Children are especially vulnerable because their bodies are still developing, leading to increased risks of respiratory infections, ear infections, more frequent and severe asthma attacks, and sudden infant death syndrome (SIDS).
Thirdhand Smoke
Thirdhand smoke refers to the invisible residue from tobacco smoke that settles on surfaces and materials like walls, furniture, carpets, clothes, and dust, lingering long after smoking has ceased. These toxins can be re-released into the air or ingested through contact. Infants and toddlers are particularly at risk because they spend more time on or near floors and frequently put their hands and objects into their mouths, leading to ingestion of these harmful chemicals. Exposure to thirdhand smoke can contribute to breathing problems like asthma and may increase the risk of other smoking-related diseases over time.