Scientists at Sahlgrenska Academy, University of Gothenburg, and Skaraborg Hospital in Skövde, Sweden, have shown that a higher BMI may be linked to higher survival rates in patients hospitalised for severe bacterial infections. The population-based study involved observations, over a nine-month period, of all 2,196 individual adults receiving care for suspected severe bacterial infection at Skaraborg Hospital in Skövde. The researchers followed the patients in this study population over time, during and after their hospital stay. The data were collected before the COVID-19 pandemic. The outcomes were reported in the paper, ‘Impact of obesity on outcome of severe bacterial infections’, published in the journal PLOS ONE.
The results show that the raised chances of survival were associated with a higher BMI in both the short and long term, at 28 days and one year after hospitalisation respectively. The differences in survival rates were clear. In the normal-weight group, 26 percent were dead within a year. The corresponding figures in the groups with higher BMI were 9-17 percent.
Occasional surveys of limited patient groups have previously shown similar results. The new findings clarify and confirm the ‘obesity survival paradox’, the researchers claim, that overweight and obesity afford protection against severe bacterial infections.
The study included 2,196 patients from a Swedish prospective, population-based, consecutive observational study of the incidence of community-onset severe sepsis and septic shock in adults. All patients with weight and height documented in the medical records on admission were included.
The case fatality rate (CFR) was negatively correlating with increasing BMI. Outcomes included 28-day CFR (p=0.002), hospital CFR (p=0.039) and one-year CFR (p<0.001). When BMI was applied as continuous variable in a multiple logistic regression together with other possible covariates, the researchers determined that BMI was associated with decreasing 28-day CFR (OR = 0.93, 95% CI 0.88–0.98, p=0.009) and one-year CFR (OR = 0.94, 95% CI 0.91–0.97, p<0.001).
"In the context of most other diseases, overweight and obesity are disadvantageous,” said Åsa Alsiö, adjunct senior lecturer in infectious diseases at Sahlgrenska Academy and senior consultant in infectious diseases at Skövde, and the study's first and corresponding author. “This applies to several types of cancer, cardiovascular disease and, in particular, COVID-19, in which a higher BMI is associated with higher mortality. Paradoxically, it's the other way round here. What we don't know," is how being overweight can benefit the patient with a bacterial infection, or whether it's connected with functions in the immune system and how they're regulated. More knowledge is needed about how being overweight affects the immune system. One patient category it could be studied in is individuals undergoing bariatric surgery."
"The COVID-19 pandemic has highlighted vulnerable patient groups, and overweight people have been hit hard. Maybe experience and handling of care for patients with severe bacterial infections can be used to improve the prognosis of COVID-19 and overweight,” explained Dr Gunnar Jacobsson, Sahlgrenska Academy and senior consultant in infectious diseases at Skaraborg Hospital in Skövde, and senior author of the study. “Globally, obesity is increasing at an alarming rate. More knowledge is needed to shed light on how body weight affects the body's defences against infection, so that treatment can be individualized.”
The researchers think there is a need for more studies, at the population level, of how BMI affects treatment outcomes in various infectious diseases and what connections with regulation of the immune system may exist.
“Overall, our results identify a relative benefit of higher BMI in cases of severe bacterial infections but also indicate higher incidence,” the authors concluded. “With the spread of obesity, more knowledge of how BMI impacts the incidence, presentation, and outcome of different types of severe infections is vital. Further population-based studies are warranted.”
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