More than one in 10 infection-related adult deaths worldwide may be linked to obesity, according to research from the University of Helsinki in Finland, published in The Lancet.
Obesity Significantly Raises Risk of Severe Infection, Death
A new analysis reveals a 70% increased risk of hospitalization or death from infection for those with obesity.
- Obesity is associated with a higher risk of hospitalization and death across a wide range of infections, including COVID-19, flu, and pneumonia.
- Individuals with class 3 obesity (a BMI of 40.0 kg/m2 or higher) were three times more likely to be hospitalized or die from infection.
- An estimated 9% to 11% of infection-related deaths globally could be prevented by addressing obesity.
- The impact of obesity on infection-related deaths varied regionally, with the highest proportions seen in North Africa and the Middle East.
The study, which analyzed data from 67,766 adults in Finland and 479,498 adults from the UK Biobank, utilized national hospitalization and death registries from 2018, 2021, and 2023. This comprehensive investigation underscores the substantial impact of obesity on infectious disease outcomes.
The Link Between Weight and Infection Severity
Researchers found that compared to individuals with a healthy weight, those with any class of obesity had a 1.7 times higher risk of experiencing a severe, potentially fatal infection. This association remained consistent across various measures of obesity—including body mass index (BMI), waist circumference, and waist-to-height ratio—and held true for diverse demographic and clinical groups.
Obesity was categorized as class 1 (30.0 to 34.9 kilograms per square meter [kg/m2]), class 2 (35.0 to 39.9 kg/m2), or class 3 (40.0 kg/m2 or higher). The average age of participants in the Finnish cohorts was 42.1 years, with 73.1% being women. In the UK Biobank group, the average age was 57 years, and 54.4% were women.
What percentage of infection-related deaths are attributable to obesity? The researchers estimated that obesity accounted for 8.6% of infection-related deaths in 2018, rising to 15.0% in 2021, and decreasing slightly to 10.8% in 2023.
The study examined 925 bacterial, viral, parasitic, and fungal infectious diseases. For the majority of these, including common illnesses like flu, COVID-19, pneumonia, gastroenteritis, urinary tract infections, and lower respiratory tract infections, obese individuals faced a greater likelihood of hospitalization or death compared to those with a healthy BMI.
Specific Infections and Regional Variations
Obesity was linked to an increased risk for almost all infection types, with hazard ratios (HRs) ranging from 1.6 for parasitic, fungal, and chronic infections to 2.0 for viral infections. Bacterial infection risks ranged from 1.7 for invasive infections to 2.1 for mycoplasma infections.
Among 10 widely studied infectious diseases, obesity showed the strongest association with skin and soft-tissue infections (HR, 2.8) and the weakest with acute pharyngitis or tonsillitis (HR, 1.5). The hazard ratio for COVID-19 was 2.3. Notably, no significant links were found for HIV (HR, 0.9) or tuberculosis (HR, 0.7).
Geographically, the highest population-attributable fraction for obesity-related infection deaths was observed in North Africa and the Middle East, reaching 18.1% in 2018, 32.1% in 2021, and 22.5% in 2023. South Asia had the lowest proportions, at 3.2% in 2018, 5.9% in 2021, and 4.1% in 2023.
“Adult obesity has been linked to specific infections, but evidence across the full spectrum of infectious diseases remains scarce,” the authors noted. “In this multicohort study with impact modelling, we examined the association between this preventable risk factor and the incidence, hospitalisations, and mortality of 925 bacterial, viral, parasitic, and fungal infectious diseases, and estimated their global and regional attributable impact.”
