Adults with the highest body mass index experienced nearly threefold higher risk of infection-related hospitalization or death, with obesity contributing to infection-related mortality worldwide, according to a recent study.
Using prospective data from more than 540,000 adults, researchers examined associations between overweight and obesity and 925 hospital-treated and fatal infectious diseases. In pooled analyses from Finnish cohorts and the UK Biobank, participants with class III obesity had nearly threefold higher risk of infection-related hospitalization or death compared with those with healthy weight, while obesity overall was associated with approximately 1.7 times the risk of severe infection. Elevated risks were observed across acute and chronic infections and across pathogen types, with the strongest associations seen for skin and soft tissue and viral infections. At the population level, obesity was estimated to account for 8.6% of infection-related deaths globally in 2018, 15.0% in 2021, and 10.8% in 2023.
These findings were based on a large prospective multicohort study that pooled participant-level data from the Finnish Public Sector study and the Health and Social Support study, with replication in the UK Biobank. The analytical sample included 67,766 adults from the Finnish cohorts and 479,498 adults from the UK Biobank, all of whom had no history of infection-related hospitalization at baseline. Body mass index (BMI) was assessed at study entry and categorized as healthy weight, overweight, or obesity, with obesity further classified as class I (30.0 to 34.9), class II (35.0 to 39.9), or class III (40.0 or higher). Participants were followed through national hospitalization and mortality registries to ascertain first occurrences of nonfatal hospital-treated or fatal infections, defined using 925 diagnostic codes spanning bacterial, viral, parasitic, and fungal diseases.
Associations between adiposity and infection outcomes were evaluated using Cox proportional hazards models adjusted for age, sex, cohort, and a broad set of baseline sociodemographic, lifestyle, and clinical covariates, including smoking status, physical activity, cardiometabolic disease, respiratory disease, and cancer. Fixed-effects meta-analyses were used to pool effect estimates across cohorts. Findings were consistent when adiposity was assessed using waist circumference and waist-to-height ratio and across subgroups defined by age, sex, ethnicity, and baseline health status. In analyses incorporating repeated BMI measurements, weight loss from obesity was associated with a modest reduction in infection risk, whereas weight gain was associated with increased risk, although risks did not return to levels observed among participants who remained at healthy weight.
To estimate the global burden of infection-related mortality attributable to obesity, pooled hazard ratios were combined with obesity prevalence and infectious mortality data from the Global Burden of Diseases, Injuries, and Risk Factors Study. These modeling analyses suggested that approximately one in ten infection-related deaths worldwide may be attributable to adult obesity, with higher proportions observed during the COVID-19 pandemic.
The researchers noted several important limitations. The observational design precludes causal inference despite consistency across cohorts and adiposity measures. BMI does not fully capture adiposity or metabolic dysfunction, and height and weight were self-reported in the Finnish cohorts, introducing potential measurement error, although results were consistent with clinically measured data from the UK Biobank. Severe infections were identified through hospitalization and mortality registries, which may have missed outpatient-managed infections. The cohorts were not fully population representative, and global burden estimates depended on modeling assumptions and the accuracy of underlying prevalence and mortality data, particularly in low-resource settings.
"Adult obesity is a risk factor for infection-related hospitalizations and mortality across diverse pathogen types, populations, and baseline clinical profiles, with evidence suggesting that approximately one in ten infection related deaths worldwide might be attributable to obesity," concluded author Solja T. Nyberg of the Clinicum, Faculty of Medicine, University of Helsinki, Finland, and colleagues.
Disclosures can be found in the study.
Source: The Lancet
