Exploring Adult Underweight Through Cluster Analysis: A Study of Socioeconomic and Health Factors in the NHANES 2011-2020 population

Background: The underweight population, defined by a body mass index (BMI) of less than 18.5, is often overlooked in clinical practice despite facing unique health risks. This study aimed to explore the distinct demographic, clinical, and anthropometric characteristics of the underweight population, utilizing data from the National Health and Nutrition Examination Survey (NHANES, 2011-2020). Methods: Cluster analysis was applied to identify subgroups within the underweight population, with a focus on key variables such as age, gender, income, and comorbidities. A total of 481 individuals with BMI <18.5 were included in the analysis, and the resulting clusters were compared to examine differences in health outcomes. Results: Four distinct subgroups of underweight individuals were identified: 1) Cluster 0 (young, healthy individuals), 2) Cluster 1 (mild-age individuals with early-stage metabolic concerns), 3) Cluster 2 (older adults with multiple chronic conditions), and 4) Cluster 3 (predominantly female individuals with comorbidities). Each cluster demonstrated unique health risks, with younger individuals presenting potential nutritional deficiencies, while older adults exhibited frailty, sarcopenia, and higher rates of chronic diseases such as arthritis, asthma, and cancer. Gender disparities were significant, particularly in Cluster 3, where women represented 67.95% of the population, highlighting the higher vulnerability of underweight women to associated health problems. Conclusion: The underweight population is heterogeneous, and BMI alone is insufficient for assessing their health risks. Different subgroups require tailored healthcare strategies, ranging from nutritional interventions for younger individuals to comprehensive geriatric assessments and chronic disease management for older adults.