It comes as no surprise that obesity is one of the most common health issues affecting the global population. In the UK alone, it is estimated that 1 in 4 adults over 18 are living with obesity,  and it is estimated that tackling obesity is currently costing the NHS approximately £6.5 billion annually.^1,2 Obesity is problematic due to its link to numerous health conditions ranging from type 2 diabetes to heart disease and cancers. Furthermore, it can also worsen existing conditions such as osteoporosis and asthma.³ Therefore, identifying, preventing, and treating obesity is essential to preventing illness and staying healthy.

In addition to the above, obesity is considered a risk factor for pulmonary embolism, however, it is not categorised as a major risk factor.⁴

In this article, we will examine what a pulmonary embolism is, its risk factors, symptoms and its relationship to obesity.

What is a pulmonary embolism?

Pulmonary embolism, or PE, is a blood clot that affects an artery in the lungs. This blood clot effectively forms a blockage and therefore restricts the flow of blood. If this occurs the consequences can be dire as the blockage to the flow of blood through the lungs can lead to tissue damage or death (i.e. pulmonary infarction) within the lungs. Further consequences include pleural effusion, which is excess fluid around the lungs, and even cardiac arrest where the heart stops beating. Therefore, PE carries a significant risk of death and disability.^5,6

What are the symptoms of PE? How do I know if I have one?

Being concerned about PE is understandable, but thankfully PE, unlike other medical conditions, is not silent. It has a set of symptoms that can be identified and necessitate emergency medical management if required.

These include:

• Unexpected shortness of breath (most common)
• Chest pain
• Lightheadedness
• Irregular heartbeat
• Feeling anxious
• Sweating
• Coughing with or without blood^6,7

If any of these occur, it is important that medical attention is sought immediately, and such an individual must be managed in a hospital emergency setting depending on severity. This usually involves treatment with an antifibrinolytic to thin the blood, dissolve the clot, and restore normal circulation.⁴

Preventing a PE

Due to the inherent danger and risk of fatality associated with PE, preventing such a condition would be very beneficial. To do this, as with many other medical conditions, a series of risk factors that can increase the risk of PE can be identified. The presence or otherwise of these risk factors can be further used to calculate a score known as a Well’s score to indicate the likeliness of a PE being present (a score of 4 or more) to inform further management.^7,8

Major PE risk factors include:

• Deep Vein Thrombosis (DVT)        
• Previous DVT or PE
• Recent surgery
• Immobility for a significant period
• Recent heart attack
• Active cancer
• Advanced age
• Pregnancy

Other risk factors may also include hormone therapy such as using contraceptives, smoking, long-duration travel and obesity.⁷

What relationship does obesity have with PE?

Even though the NICE guidance for the NHS denotes obesity as a non-major risk factor for PE, there exists a relationship between the two. A systematic review in 2005 looked at the incidence of PE and DVT in obese patients over a 20-year period (1999 to 1979) and found that the risk of PE (as well as DVT) was higher in obese patients, particularly in women under 40.⁹

Similarly, another study over 10 years observed discharged patients from short-stay hospitals in the USA and included patients who were obese and non-obese. It was found that the risk of PE was highest among obese patients aged 11–20 years, particularly in obese women. Furthermore, mortality from PE was 4.3% compared with 9.5% in non-obese patients. However, this study also found that in obese patients who didn’t undergo PE treatment, mortality was 3.8% compared to 8.4% in non-obese patients. This indicates a higher risk of developing PE in obese patients. This protective nature was also seen in a study conducted in 2011 which looked at adverse in-hospital outcomes with PE in patients of varying weights. For nearly 3 years a German in-patient database categorized patients as obese, underweight, overweight and normal weight. The study revealed that although the incidence of PE was greater in obese patients, non-obese patients had lower mortality. Such evidence points towards a potential paradox with regard to the relationship between PE and obesity.¹⁰

Nevertheless, despite the paradox with mortality, obesity seems to be a significant risk factor for PE.

How can PE be linked with obesity?

Obesity is related to a sedentary lifestyle and inactivity. Another study found that an increased risk of PE was seen with obesity. However, it also noted that the underlying reasons for this may be biological. It is also linked with increased pressure within the abdomen, inflammation, reduced fibrinolysis, increased fibrinogen, von Willebrand factor and factor VII. These factors lead to an increased level of blood clotting and thus an increased risk of venous thrombosis or blood clot formation. This explains the risk of thrombosis being increased when obesity is present.¹¹ In addition to factors such as age.

Summary

There is a strong link present between obesity and PE. One possible reason for the increase in PE risk may be due to certain biological factors, however, more research is required. Although there may be a protective element that obesity may confer with PE, the risk from obesity is still significant and should not be encouraged. It is worth reiterating the fact that obesity is problematic for human health and is a risk factor for PE as well as other major diseases and that its increase should be prevented as this will lead to worsening health outcomes.