Nationwide trends in prevalence of underweight, overweight, and obesity among people with disabilities in South Korea from 2008 to 2017

The study addresses how body weight distribution (underweight to severe obesity) has changed over a decade in South Korea and whether these trends differ by disability status, type, and severity. Maintaining optimal body weight is crucial for preventing chronic diseases and mortality; obesity is linked to metabolic and cardiovascular conditions, whereas underweight is associated with osteoporosis, sarcopenia, low fertility, anemia, and higher mortality. While global and Korean obesity prevalence has risen, underweight persists in vulnerable groups, including people with disabilities. Prior research predominantly examined specific disability types or relied on self-reported measures, leaving a gap in comprehensive, population-level, longitudinal assessments across disability types and grades. Leveraging Korea’s universal health insurance and medical certification-based disability registration allows robust linkage to examine nationwide trends and disparities.

Design and data sources: Serial cross-sectional analysis using the National Health Information Database (NHID) general health checkup data linked to national disability registration data in South Korea, 2008–2017. The NHID includes health care utilization, health screening, socio-demographics, and mortality for the entire population insured by the National Health Insurance Service (NHIS). Adult general health checkups (≥19 years) are offered biennially; participation increased from 65.3% (2008) to 78.5% (2017). The disability registry (covering 93.8% of the disabled population in 2011) provides medically certified type and severity of disability. Population: 123,334,034 health checkup participants across 2008–2017; in 2017, 14,246,785 adults aged 19–110 years (53.1% men). Measures: Anthropometry (weight, height, waist circumference) from examinations. BMI calculated as kg/m². Categories based on WHO Asia-Pacific cut-offs: underweight <18.5; normal 18.5–<23.0; overweight ≥23.0–<25.0; obesity ≥25.0–<30.0; severe obesity ≥30.0. Abdominal obesity defined as waist ≥90 cm (men) and ≥85 cm (women). Disability: Fifteen types per registry; severity graded 1 (very severe) to 6 (very mild), grouped as severe (1–3) and mild (4–6). Covariates: Age, sex, insurance type, income (Medical Aid; 1st–4th premium quartiles), residence (metropolitan/urban/rural), health behaviors (smoking with pack-years, alcohol use; heavy drinking defined as ≥7 drinks for men or ≥5 for women on a single occasion at least twice/week), physical activity (moderate-intensity or walking ≥30 min, days/week), and Charlson comorbidity index (0, 1–2, 3–4, ≥5). Statistical analysis: Descriptive statistics for baseline characteristics. Trends in mean BMI and waist circumference assessed by t-test/ANOVA. Age-standardized prevalence of underweight, obesity, severe obesity, and abdominal obesity computed annually via direct standardization to the 2005 Korean Census population. Multinomial logistic regression (reference: normal BMI 18.5–<23.0) estimated adjusted odds ratios (ORs) for underweight, overweight, obesity, and severe obesity by disability status, severity, and type using 2017 data, adjusting for age, income, residence, smoking, alcohol, moderate physical activity, walking, and Charlson index. Two-sided p<0.05 considered significant. Ethics: Data anonymized; IRB approval from Chungbuk National University (CBNU-202010-HRHR-0171).

- Sample and demographics: Each year >10 million adults were included; 2017 included 14,246,785 adults aged 19–110 years (53.1% men). In 2017, 729,288 (5.1%) had disabilities; 27.5% of them had severe disabilities. People with disabilities were older (60.7±13.5 vs. 49.0±14.1 years), had lower incomes, more rural residence, and higher comorbidity burden than those without disabilities. - BMI and waist trends (2008–2017): Mean BMI and waist circumference increased significantly in all groups (p for trend <0.001). Individuals with disabilities consistently had higher BMI and waist circumference than those without disabilities. Sex-specific patterns differed: women with disabilities had higher BMI than women without; among men, those with disabilities had lower mean BMI than men without disabilities. - Underweight trends: Age-standardized underweight prevalence declined among those without disabilities (from 5.3% in 2008 to 4.5% in 2017). Among people with disabilities, underweight rose in 2012 and then remained steady. Underweight prevalence was higher in women than men regardless of disability. - Obesity trends: Age-standardized obesity, severe obesity, and abdominal obesity increased over time across all groups. The obesity gap between women with vs without disabilities widened (difference 8.7% in 2008 to 12.0% in 2017). Severe obesity disparities in women widened markedly (2.6% to 5.3%). Among men, obesity prevalence between disability groups converged, but severe obesity gaps increased. - 2017 adjusted odds by disability (multinomial models): • Underweight: Disability associated with higher odds (men OR 1.41, 95% CI 1.38–1.44; women OR 1.31, 1.28–1.34). Severe disability particularly elevated underweight odds (men OR 2.00, 1.94–2.06; women OR 1.83, 1.77–1.89). Nearly all disability types (except facial) increased underweight odds. • Overweight/obesity/severe obesity—men: Overall disability linked to slightly lower odds of overweight (OR 0.93) and obesity (OR 0.95) but higher odds of severe obesity (OR 1.05). By severity: severe disability associated with lower obesity odds (OR 0.79) but higher severe obesity odds (OR 1.12); mild disability with slightly higher obesity odds (OR 1.03) and lower severe obesity odds (OR 0.92). • Overweight/obesity/severe obesity—women: Disability increased odds of overweight (OR 1.12), obesity (OR 1.40), and severe obesity (OR 2.08) regardless of severity; severe and mild disabilities both showed strong associations with severe obesity (OR ~2.07–2.10). • By disability type: In women, severe obesity odds were highest for mental disorders (OR 5.71, 95% CI 5.35–6.10), autism (OR 5.21, 2.79–9.72), and intellectual disability (OR 4.04, 3.81–4.27). In men, severe obesity was elevated with autism (OR 1.46) and mental disorders (OR 1.63). Physical disability was associated with higher obesity odds in both sexes (e.g., women OR 1.59; men OR 1.03) and higher severe obesity (women OR 2.51; men OR 1.16). - Abdominal obesity: Paralleled general and severe obesity trends, with higher prevalence and widening disparities among women with disabilities. - Notable subgroup patterns: Underweight was more frequent in men with severe disabilities (6.9% vs 2.6% mild). Women showed high underweight regardless of severity (8.5% severe vs 7.5% mild).

The study demonstrates that disability status is associated with a polarized weight distribution—higher risks of both underweight and severe obesity—addressing the research question about differential trends by disability. The persistence of underweight among people with disabilities, contrasted with declines among non-disabled individuals, suggests unmet nutritional and functional needs, especially in severe and internal organ disabilities (respiratory, renal, liver, heart). The widening gaps in obesity and severe obesity among women with disabilities highlight intersectional vulnerabilities linked to sex, disability severity, and disability types (mental, intellectual, developmental), compounded by older age, lower income, and possibly social pressures regarding body image and disparities in healthcare access and quality. The findings underscore the need for targeted, inclusive health policies and interventions that address both ends of the weight spectrum, considering tailored strategies for specific disability types, sex, and severity, as well as structural determinants (socioeconomic status, care environments, medication effects, and opportunities for physical activity).

From 2008 to 2017 in South Korea, obesity and severe obesity increased among adults irrespective of disability status, while underweight decreased only among those without disabilities. Disability was associated with higher odds of both underweight and obesity, with the most pronounced severe obesity among women with severe, mental, or developmental disabilities. Public health strategies should simultaneously target prevention and management of underweight and obesity in people with disabilities, with focused efforts on high-risk subgroups. Future research should clarify mechanisms (e.g., healthcare access, living arrangements, medication use, physical activity constraints), monitor trends beyond 2017, and evaluate tailored interventions to reduce disparities.

- Selection bias: Analyses included individuals who attended health screenings; very old adults or those with severe disabilities may be underrepresented due to reduced access, potentially underestimating extremes of weight. - Unmeasured confounding: Important variables such as energy intake, living/residence type (e.g., institutional vs family), and whether disabilities were congenital or acquired were unavailable in NHID. - Measurement limitations: Although anthropometrics were measured, data for individuals unable to stand may be inaccurate or missing. - Potential ascertainment changes: The sharp rise in underweight in 2012 among people with disabilities may reflect increased screening after implementation of a national personal assistance service rather than a true prevalence shift.