Published in the journal Critical Care Medicine, the study raises interesting questions about how obesity affects the body's response to infection. Most studies have linked it to worse, not better health outcomes.
Lead author Dr. Hallie C. Prescott, a pulmonary and critical care medicine clinical lecturer at the University of Michigan (U-M) Health System in Ann Arbour, says:
"Physicians expect obese patients to do poorly, and this belief can affect the care and counseling they provide to patients and their families. Our study indicates obese sepsis patients actually have lower mortality and similar functional outcomes as normal weight patients."
Rates of sepsis have increased in the US
Sepsis, sometimes referred to as blood poisoning or septicaemia, is a potentially life-threatening condition where the body's immune system overreacts to an infection, which may result in septic shock. Affected patients often have to spend time in the intensive care unit.
According to research that shows it affects around 750,000 patients and kills over 250,000 Americans a year, sepsis is the leading cause of death in US hospitals.
Incidence of sepsis in the US has doubled in the last 15 years, making it an increasingly important subject of research and area of spending in Medicare.
Medicare spending on sepsis now costs more than $16 billion a year in hospital bills, which is about four times the total hospital bill for heart attacks. The Medicare system now pays for around a million hospitalizations a year due to severe sepsis.
Most patients who survive severe sepsis need rehabilitation care in a specialist facility. Around half of survivors die within a year of leaving the hospital.
Obese patients less likely to die within a year of hospitalization for severe sepsis
Evidence of a link between obesity and improved chance of surviving sepsis has been mounting for a while, but it has attracted criticism in that it could be biased by not properly accounting for preferential admission of obese patients to critical care. Also, those studies have not necessarily followed up patients after they leave the hospital and looked at other health outcomes.
The study found that patients with a higher BMI were less likely to die after being treated for sepsis within a year of leaving the hospital.
For their study, Dr. Prescott and colleagues set out to examine whether "1-year mortality, healthcare utilization, and functional outcomes following a severe sepsis hospitalization differ by body mass index."
They examined data on 1,404 older Medicare beneficiaries hospitalized with severe sepsis who were enrolled in a nationally representative study. Of the participants, 334 (23.8%) were obese or severely obese, 473 (33.7%) were overweight and 597 (42.5%) were normal weight.
They found that patients with a higher body mass index (BMI) were less likely to die within a year of leaving the hospital after treatment for severe sepsis.
They also found there was a "dose-response relationship" between BMI and mortality, with severely obese patients showing a lower rate of mortality than obese patients.
In terms of functional outcomes, they found the obese patients fared just as well as the normal weight patients, noting that "total function limitations following severe sepsis did not differ by body mass index category."
The results also showed that the total time spent in hospital and rehabilitation care was greatest among obese patients, as was Medicare spending, but average daily use and average daily Medicare spend was about the same for normal weight and obese survivors of severe sepsis.
Senior author Theodore Iwashyna, assistant professor of internal medicine at the U-M Health System, says:
"Obese patients who survive their sepsis hospitalization use more health care resources and require more Medicare spending - but this apparent increase in resource use is a result of living longer, not increased use per day alive."
The authors note excess weight may cause the body to respond differently to critical illness, and more studies should be done to understand why, so health care providers can improve care for all patients with sepsis and other critical conditions.
In October 2013, researchers in the UK reported how they were developing a rapid bedside blood test for sepsis that returns results within 2 hours. Such a test could save thousands of lives worldwide every year by ensuring sepsis patients get prompt treatment with the correct antibiotic for the particular bacteria behind their infection.