Adults with obesity are 70% more likely to get severe infections that lead to hospitalization or death, with the most severe cases of the condition facing three times the risk, according to the new study results.
The prospective multicohort study of more than 540,000 participants found that obesity may be the driving factor in up to 11% of deaths from infectious diseases. The study linked obesity to health risks including pneumonia, influenza, COVID-19, gastroenteritis and UTIs, along with fungal and parasitic infections.
“I was surprised by the wide range of severe infections that obesity is associated with,” Mika Kivimäki, PhD, chair of social epidemiology and professor at University College London, told Healio, while noting that the study did not find an associated between obesity and HIV or tuberculosis.
The study included 67,766 adults (mean age, 42.1 years; 73.1% women) from the Finnish Public Sector study and Finnish Health and Social Support study and 479,498 adults (mean age, 57 years; 54.4% women) from the UK Biobank with no recent infection-related hospitalizations. Kivimäki and colleagues assessed BMI at baseline, with participants categorized as having healthy weight, overweight or obesity, the latter further classified as class I, II or III. After baseline assessment, the researchers followed participants first infection, death or end of follow-up (mean, 14.1 years).
There were 8,230 and 81,945 incident infections in the Finnish and UK Biobank cohorts, respectively, with individuals with class III obesity vs. healthy weight exhibiting a three-fold higher risk for infection-related hospitalization, death or either outcome. Further, those with any obesity exhibited a pooled hazard ratio for either fatal or non-fatal severe infection of 1.7 (95% CI, 1.7-1.8), a finding that persisted across obesity indicators, demographic and clinical subgroups, and various infections.
“At the population level, a two- to three-fold increase indicates a major public health risk factor,” Kivimäki said.
The researchers used these risk estimates and data from the Global Burden of Diseases, Injuries and Risk Factors Study to measure the proportion of infection-related deaths due to obesity, which were estimated to be 8.6% (95% CI, 6.6%-11.1%) in 2018 before the COVID-19 pandemic, 15% (95% CI, 12.8%-17.4%) in 2021 during the pandemic and 10.8% (95% CI, 8.6%-13.6%) in 2023 after the pandemic.
According to a press release, the research also showed the rate of infection-related deaths linked to obesity varied globally. For instance, the rate was one in four deaths in the United States and roughly one in six in the United Kingdom. Vietnam had the lowest rate (1.2%) of infection deaths caused by obesity.
“As obesity rates are expected to rise globally, so will the number of deaths and hospitalizations from infectious diseases linked to obesity,” lead study author Solja T. Nyberg, PhD, bioinformatician at the University of Helsinki, said in the press release.
“To reduce the risk of severe infections, as well as other health issues linked with obesity, there is an urgent need for policies that help people stay healthy and support weight-loss, such as access to affordable healthy food and opportunities for physical activity,” Nyberg continued.
Kivimäki said the findings show how obesity is a risk factor for many severe infections, not just COVID-19 and influenza, and that he hopes the study will impact vaccine guidelines for people with obesity.
“Our findings may provide expert panels with additional evidence to consider when updating vaccination policies,” Kivimäki said. “I also hope our study raises awareness … [that] people with obesity should treat infections carefully and ensure their vaccinations are up-to-date.”
