Can smoking alone cause polycythemia with elevated Hemoglobin (Hgb) and Hematocrit (Hct) levels?

From the Guidelines

Yes, smoking can cause polycythemia with elevated hemoglobin (Hgb) and hematocrit (Hct) levels, a condition known as secondary polycythemia or erythrocytosis. Chronic exposure to carbon monoxide in cigarette smoke reduces oxygen-carrying capacity of the blood, leading the body to compensate by increasing red blood cell production. This occurs because carbon monoxide binds to hemoglobin with greater affinity than oxygen, forming carboxyhemoglobin, which triggers the kidneys to release erythropoietin, stimulating bone marrow to produce more red blood cells 1. The values mentioned are elevated beyond normal ranges and consistent with smoking-induced polycythemia. However, it's essential to rule out other causes of polycythemia, such as polycythemia vera (a bone marrow disorder), sleep apnea, high-altitude living, certain kidney diseases, or other lung diseases.

Some key points to consider:

• Smoking cessation is the primary treatment, which can normalize these values over time, typically within 2-3 months 1.
• Regular monitoring of complete blood counts is recommended during this period.
• The pathophysiological effects of smoking are multifactorial, affecting both the systemic vasculature and blood rheology, and are associated with increased fibrinogen levels, increased platelet aggregation, decreased high-density lipoprotein (HDL) cholesterol levels, and increased hematocrit 1.
• All patients with polycythemia should be managed aggressively for their generic cardiovascular risk factors and advised to stop smoking 1.

It's crucial to prioritize the patient's overall health and well-being, focusing on reducing morbidity, mortality, and improving quality of life. Therefore, smoking cessation and regular monitoring are essential for managing smoking-induced polycythemia.

From the Research

Polycythemia and Smoking

• Smoking has been linked to an increased risk of developing polycythemia, a condition characterized by elevated hemoglobin (Hgb) and hematocrit (Hct) levels 2, 3, 4, 5.
• Studies have shown that smokers are more likely to have elevated Hgb and Hct levels compared to non-smokers, with one study finding that smokers had significantly higher levels of Hgb and Hct than non-smokers 5.
• The mechanism behind smoking-induced polycythemia is thought to be related to the increased levels of carboxyhemoglobin in smokers, which can lead to a left-shifted oxygen-hemoglobin dissociation curve and increased red blood cell production 4.

Secondary Polycythemia in COPD

• Secondary polycythemia is a common complication of chronic obstructive pulmonary disease (COPD), and smoking is a major risk factor for developing COPD and secondary polycythemia 3.
• A study of COPD patients found that current smoking, severe resting hypoxemia, and impaired diffusing capacity for carbon monoxide were associated with an increased risk of secondary polycythemia 3.

Effects of Smoking Cessation

• Smoking cessation has been shown to decrease Hgb and Hct levels in smokers, with one study finding that symptoms of polycythemia disappeared and red blood cell volume decreased in patients who reduced their smoking habit 4.
• Another study found that quitting e-cigarette use led to a decrease in Hgb and Hct levels in a patient with e-cigarette-induced polycythemia 2.

Haematological Parameters in Smokers

• Smoking has been shown to have adverse effects on haematological parameters, including increased white blood cell count, Hgb, mean corpuscular volume, and mean corpuscular hemoglobin concentration 5.
• These alterations may be associated with an increased risk of developing atherosclerosis, polycythemia vera, chronic obstructive pulmonary disease, and cardiovascular diseases 5.