Smoking – the undiscussed burden.

It is well established that smoking is directly linked to lung cancer—a fact recognized as early as the 1950s. Among the approximately 7,000 chemicals found in cigarette smoke, at least 70 are identified as causative agents for lung cancer. People who smoke have a 15- to 30-fold higher risk than those who do not.

The somewhat positive thing about lung cancer is that the risk drops significantly when smoking is ceased. Studies have shown a steep decline in risk as low as 39.7% within 5 years of cessation of smoking compared to the currently smoking group, according to the Framingham Heart Study.

While smoking cessation can significantly reduce the risk of lung cancer, its effects on another major health issue—atherosclerosis—are less easily reversed.

Atherosclerosis is a chronic inflammatory disease in which there is accumulation of lipids, fibrous elements, and calcification within the large and medium sized arteries, with immune cells (like macrophages) playing a crucial role.

This leads to narrowing of the vessel lumen and damages the innermost layer of the blood vessel—the intima (a condition also referred to as endothelial dysfunction). Such dysfunction initiates a cascade of events that results in atherosclerotic plaque formation. As plaques enlarge, they further narrow the vessels and reduce blood flow.

In the initial stages, if disease-causing factors—such as smoking or high blood pressure—are eliminated, vessels can undergo a remodeling process to maintain their lumen size. However, if these factors persist, the vessel may develop blood clots (an acute thrombotic event), potentially leading to a complete loss of blood supply to the affected organ.

Atherosclerosis is a major contributor to various cardiovascular diseases, including coronary artery disease, stable angina, acute coronary syndromes, stroke, peripheral vascular disease, erectile dysfunction, and aortic aneurysms (enlargement of the large abdominal artery), among others.

While cannot be attributed to just smoking alone; out of the 17 million premature deaths (under the age of 70) due to noncommunicable diseases in 2019, 38% were caused by cardiovascular diseases. That's significant morbidity burden caused by atherosclerotic disease.

Not just heart disease, atherosclerotic disease can lead to limb loss due to acute limb ischaemia, significantly affecting quality of life, in some cases bed bounding the patient. And this is known to be linked to smoking compared to heart diseases.

Due to the large number of patients affected by atherosclerotic disease, the economic burden on both individuals and the healthcare system is immense. According to a recent publication by the American Heart Association, health care costs associated with cardiovascular risk factors in the United States are projected to triple between 2020 and 2050—from $400 billion to $1,344 billion (adjusted for inflation). A similar trend may be seen in Sri Lanka, where almost the entire economic burden of cardiovascular disease falls on taxpayers.

With more cardiovascular events, ischaemic strokes, ischaemic limbs showing up; we must recalibrate our thoughts in realising the true burden of smoking is not just lung cancer.

Further measures must be taken to reduce the risk factors associated with atherosclerotic diseases.

There are two types of risk factors;

1. Non-modifiable risk factors;

• Age
• Sex
• Genetic factors
• Ethnicity

2. Modifiable risk factors;

• High Blood Pressure
• Diabetes Mellites
• Smoking
• Alcohol Consumption
• Lack of Physical activity
• Psychological stressors.

The general population must be educated and empowered to address modifiable risk factors. Only by addressing these factors before the onset of disease can we truly mitigate the economic and human resource burden caused by atherosclerotic disease.

References

1. Lung Cancer Risk Factors - https://www.cdc.gov/lung-cancer/risk-factors/index.html
2. Early landmark studies of smoking and lung cancer - https://academic.oup.com/jnci/article/110/11/1201/4996947
3. Lifetime Smoking History and Risk of Lung Cancer: Results From the Framingham Heart Study - https://academic.oup.com/jnci/article/110/11/1201/4996947
4. Smoking and Atherosclerosis: Mechanisms of Disease and New Therapeutic Approaches - https://www.ingentaconnect.com/content/ben/cmc/2014/00000021/00000034/art00004
5. Pathophysiology of Atherosclerosis - https://www.ncbi.nlm.nih.gov/books/NBK507799/
6. Cardiovascular diseases (CVDs) - https://www.who.int/news-room/fact-sheets/detail/cardiovascular-diseases-(cvds)
7. Cigarette Smoking and Progression of Atherosclerosis - The Atherosclerosis Risk in Communities (ARIC) Study - https://jamanetwork.com/journals/jama/fullarticle/1150354
8. Active smoking is associated with higher rates of incomplete wound healing after endovascular treatment of critical limb ischemia - https://pmc.ncbi.nlm.nih.gov/articles/PMC8076886/
9. Risk Factors and Epidemiology of Atherosclerosis - https://pressbooks.bccampus.ca/pathology/chapter/risk-factors-and-epidemiology-of-atherosclerosis/