Loading ...

Scientific evidence has shown that there is no safe level of exposure to smoke; even brief contact with smoke can increase the risk for respiratory diseases, asthma, allergies, and various types of cancer.

Smoking is far more than a threat to respiratory and cardiovascular health. A growing number of scientific studies have confirmed that systemic addiction causes persistent injury to multiple organs. It weakens the immune system, triggers structural and functional changes in the brain, and contributes to a decline in mental health. It also disrupts the gut microbiota and promotes diseases of the liver, kidneys, and pancreas.

In summary, tobacco damage extends well beyond the lungs and heart and affects the entire body. Vaping has surged in popularity in this unhealthy landscape, with the belief that it is less harmful. However, recent studies have refuted the notion that e-cigarette use is linked to higher rates of asthma and chronic obstructive pulmonary disease (COPD). 

The aerosols emitted by these devices also contain carcinogens, creating an additional long-term hazard. It is indisputable that smoking causes premature death; however, this warning seems to fall on deaf ears among smokers and younger people. The numbers are stark. 

According to the World Health Organization, tobacco kills more than 8 million people annually. Of these, over 7 million die from direct use, while about 1.3 million are nonsmokers exposed to secondhand smoke.

Tobacco accounts for 90% of lung cancer deaths, 95% of COPD fatalities, 50% of cardiovascular mortality, and 30% of all cancer deaths. Half of all smokers will die of a tobacco-related disease, losing an average of 10-15 years of life compared with nonsmokers. In summary, smoking is the single most preventable cause of death and illness in Spain and other developed nations.

Immune Impact

One of the most serious effects of tobacco is the deterioration of the immune system. Several clinical studies have shown that smoking weakens the body’s natural defense mechanism, reducing its ability to fight bacterial, viral, and fungal infections.

Tobacco smoke directly harms neutrophils and lymphocytes, diminishing their chemotaxis and phagocytosis capabilities and weakening the body’s defenses against infections. Furthermore, a high prevalence of mucosal lesions, including leukoplakia, nicotinic stomatitis, and melanosis, occurs, some of which carry a risk for malignant transformation. 

A large study conducted in Korea and published in the Journal of Cancer Prevention compared natural killer cell activity among 12,249 participants. Smokers had significantly lower interferon gamma levels (median, 1422 pg/mL) than former smokers (1791 pg/mL) and nonsmokers (1504 pg/mL). The more a person smokes, the greater the reduction in immune function.

Another in vitro study using peripheral blood mononuclear cells from asymptomatic smokers showed that these cells secreted higher levels of proinflammatory cytokines, such as interleukin (IL)-1 beta, IL-6, and TNF alpha receptor, but had reduced natural killer cytotoxic activity after stimulation. In other words, the body responds with increased inflammation but with reduced defense capability.

Nicotine further alters the behavior of other immune cells; although they survive longer and migrate more readily to infection sites, their ability to eliminate bacteria and viruses is reduced. For example, in the lungs, macrophages lose part of their pathogen recognition function, further weakening the body’s response.

Smokers also generate fewer protective antibodies after receiving vaccines, such as hepatitis B, and exhibit elevated levels of antibodies associated with abnormal immune responses.

Cellular Effects

When a person smokes a cigarette, the cells in the mouth, nose, and throat are the first to suffer the impact of smoke. More than 50 carcinogens in tobacco dissolve instantly in saliva and nasal fluids, spreading across the oral and nasopharyngeal epithelium. These substances cause oxidative damage, cell death, and DNA damage, which, when repaired, can introduce mutations that lead to cancer. Smoking is a major risk factor for oral cancer.

In a clinical study, gingivitis was induced in smokers who were asked to forgo oral hygiene . Although smokers experienced less gingival bleeding than nonsmokers, they had higher pathogenic bacterial counts, and levels of key immune-regulatory cytokines, including IL-8, IL-17, and interferon gamma, were higher in smokers than in nonsmokers.

Another study comparing 200 smokers with 100 nonsmokers found that smokers’ salivary microbiota were less diverse, dominated by potentially pathogenic genera such as Streptococcus, Prevotella, and Veillonella, with significant correlations with lipid biomarkers. 

Digestive Impact

Chronic exposure to tobacco leads to a range of changes in oral health, including impaired gingival microcirculation, characterized by increased vascular tortuosity, reduced capillary diameter, and decreased blood perfusion. These changes hinder healing and diminish the visible signs of inflammation, ultimately contributing to the development and progression of periodontal disease.

Smokers experience more dental caries due to an oral microbiota dominated by Streptococcus mutans, a more acidic salivary pH, reduced saliva flow, and lower immunoglobulin A levels. Tobacco reduces the sense of taste and smell and causes a persistent bitter taste due to the loss of nerve transmission capacity in the sensory organs.

In the mouth, esophagus, and stomach, tobacco weakens the sphincter that closes the esophageal inlet, promoting gastroesophageal reflux and frequent heartburn. It also increases the incidence of peptic ulcers in the stomach and intestines, impeding healing and increasing the likelihood of Helicobacter pylori infections.

Smoking disrupts the balance of gut microbiota and decreases mucosal blood flow, leading to chronic inflammation and increased intestinal permeability. Studies have shown reduced levels of beneficial bacteria, such as Bifidobacterium, and changes in the proportion of other strains, which can worsen inflammatory conditions, such as Crohn’s disease. Other studies have linked smoking to a higher risk for gallstones, worsening liver disease, more frequent pancreatitis, and digestive system tumors in the mouth, esophagus, stomach, pancreas, liver, colon, and rectum.

Impact on the Nervous System

Nicotine, the main addictive component of tobacco, is responsible for the pleasurable sensations experienced by the brain when smoking. Once in the bloodstream, it reaches the adrenal glands, triggering the release of adrenaline, which raises the blood pressure, accelerates the heart rate, and increases the respiratory rate.

This adrenaline rush generates a pleasant sensation. Nicotine also targets neuronal nicotinic receptors that transmit nerve signals. With continued use, these receptors become less sensitive or decrease in number, requiring higher nicotine doses to achieve the same effects. This mechanism generates dependence because nicotine alters brain chemistry and modifies decision-making and impulse control.

The consequences extend beyond addiction, and persistent receptor changes have been linked to neurologic and mental health problems. For instance, memory loss, myasthenia gravis (muscle weakness from impaired nerve-muscle connections), neuropathic pain, insomnia, and difficulty concentrating. Smoking also increases the risk for schizophrenia, psychosis, depression, anxiety, and neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases, with cognitive deficits that can persist after quitting.

Brain Aging

Tobacco also accelerates the natural aging of the brain. A decade-old study in the UK found that the cerebral cortex of smokers thinned at a faster rate than that of nonsmokers. This shrinkage of the cerebral cortex damages regions linked to basic functions such as memory, attention, language, and consciousness. It also increases the risk for cognitive decline, dementia, and cerebrovascular diseases. Smokers who quit smoking regained some of their original cerebral cortex size, suggesting that it can regenerate. Researchers have noted that quitting smoking is the best way to reduce the risk for brain damage, dementia, and other mental health disorders.

Metabolic Effects

In the endocrine and metabolic systems, nicotine can disrupt metabolism and appetite regulation by affecting the hypothalamic-pituitary-adrenal axis, which governs the stress response. These hormonal disturbances can influence body weight, fat distribution, and cortisol response, among other vital functions. Smoking-induced dysbiosis also increases the risk for metabolic diseases by altering the gut microbiota.

Of particular concern are the effects of tobacco on the fetus during pregnancy, which raise the risks for preterm birth, low birth weight, and stillbirth. Infants born to mothers who smoke experience more respiratory, cardiovascular, and allergic problems during childhood. Tobacco also leaves visible marks on the appearance, causing premature skin aging, poor wound healing, halitosis, and persistent yellowing of the teeth.

Smoking has been linked to a higher risk for blindness, hearing loss, osteoporosis, chronic lower back pain, endothelial dysfunction, arrhythmia, lung injuries, structural heart changes, and peripheral vascular disease.

Passive Exposure

All these effects occur in smokers, but a major concern is the risk tobacco poses to nonsmokers via passive exposure to tobacco, even in open spaces, known as secondhand smoke.

Scientific evidence showed that there was no safe level of exposure; even brief contact with smoke could increase the risk for respiratory diseases, asthma, allergies, and various cancers.

In Spain alone, secondhand smoke caused an estimated 747 deaths among individuals older than 35 years of age in 2020. It indirectly contributed to approximately 1.3 million deaths annually. For every smoker, air pollution on terraces rises by up to 30%, and toxins adhere to clothing, hair, and surfaces, posing a hazard even after the cigarette is put out.

The impact is particularly severe in exposed children, who suffer a 70% higher risk for respiratory infections and a higher risk of developing cancer in adulthood if exposed early in life. Nonsmokers exposed to secondhand smoke also have a higher risk for heart attack and stroke. In pregnant women, exposure increases the likelihood of stillbirth and other fetal complications.

This story was translated from El Medico Interactivo.