Higher body mass index improves survival in severe infections

Disease and treatment 7. jun 2021 2 min PhD, MD Sigrid Gribsholt Written by Kristian Sjøgren

Having a higher body mass index (BMI) can have advantages. New research indicates that higher BMI is associated with a lower risk of dying from infections requiring hospitalization.

Higher BMI is associated with an increased risk of dying from various diseases, including cancer and cardiovascular disease.

However, new research from Denmark shows that this relationship is reversed for the risk of dying from severe infections.

A major study of registry data from more than 35,000 people in the Central Denmark Region shows that people with obesity were 50% less likely to die than people of normal weight after being hospitalized with an infectious disease.

Conversely, people who were underweight were twice as likely to die from an infection as people of normal weight.

“The results can be viewed in a broader research context of identifying the health effects of overweight. Having overweight is mostly associated with increased risk, but people with overweight and obesity have a lower risk of dying from an infection requiring hospitalization,” explains a researcher behind the study, Sigrid Gribsholt, Department of Clinical Epidemiology, Aarhus University and Department of Endocrinology and Diabetes, Aarhus University Hospital.

The research has been published in Mayo Clinic Proceedings.

Data from more than 35,000 people

Sigrid Gribsholt and colleagues examined data from 35,406 people with a recorded BMI hospitalized in Denmark with a primary infection diagnosis from 1 January 2011 to 30 September 2015.

The most common infections requiring hospitalization were urinary tract infections, pneumonia, sepsis and skin infections.

The researchers categorized the participants as being underweight, of normal weight, overweight and obese based on their recorded BMI and then determined whether these groups differed in the risk of dying within 90 days after hospitalization.

The researchers also examined how comorbid conditions affected the risk of dying after hospitalization, including cancer, tobacco smoking and recent weight changes.

10% of people hospitalized with infections die

The results showed how many people died within 90 days after hospitalization:

  • · 10% (3,479 of 35,046) of those hospitalized for any infection;
  • · 11% (466 of 4,425) of those hospitalized with a urinary tract infection;
  • · 17% (1,536 of 8,855) of those hospitalized with pneumonia;
  • · 25% (115 of 1,831) of those hospitalized with sepsis; and
  • · 6% (114 of 1,831) of those hospitalized with a skin infection.

The groups with higher BMI performed better than others.

  • · People with overweight or obesity had only half the risk of dying of normal-weight people.
  • · Underweight people had twice the risk of dying of normal-weight people.

Immune system constantly prepared to combat infections

Sigrid Gribsholt explains that being overweight seems to protect against death from infections for several reasons and that being underweight seems to be an extra risk factor when a person is hospitalized with an infection.

Being overweight or obese may be associated with increased inflammation. This is intrinsically unhealthy but may also mean that the immune system is already on alert and ready to fight an infection when it arises.

Another explanation may be that doctors are more careful in treating patients with overweight and obesity because they consider them as having higher risk.

According to Sigrid Gribsholt, people who are underweight may have an unrecognized underlying disease contributing to twice the risk of death of normal-weight people.

“We cannot use the study to infer causes – only associations. However, people with overweight may have increased energy reserves that may protect them against death from severe infections. However, we note that overweight may not be associated with any overall health benefit. Obesity is still associated with an increased risk of both physical and mental disorders,” says Sigrid Gribsholt.

Many still die from infections

According to Sigrid Gribsholt, the new research results can be used to create extra awareness about the higher risk underweight people have of dying from an infection.

Sigrid Gribsholt says that doctors need to be more aware of these people when they are hospitalized with an infection.

“Our results also show that, regardless of weight, many still die from infectious diseases. This still needs to be taken seriously, and we need to be aware of people’s other comorbidities and how their BMI may be associated with the risk of a serious and potentially fatal disease trajectory,” explains Sigrid Gribsholt.

Body mass index and 90-day mortality among 35,406 Danish patients hospitalized for infection” has been published in Mayo Clinic Proceedings. The study received funding through the Program for Clinical Research Infrastructure (PROCRIN) established in 2014 by the Lundbeck Foundation and the Novo Nordisk Foundation.

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