Trends in underweight and severe underweight disparities in Korean adults and older adults: a nationwide, repeated cross-sectional study

Objectives: Little is known about the disparities in underweight prevalence among the general population in high-income countries. We investigated the trends in underweight prevalence and disparities across sociodemographic groups among Korean adults and older adults. Setting and participants: A series of cross-sectional data on Korean national health checkups for adults aged >= 20 years were analyzed from 2005 to 2016. Measurements: Based on body mass index (kg/m(2)), underweight was graded as mild (17.0-18.49), moderate (16.0-16.9), and severe (<16.0). Underweight prevalence was compared across sociodemographic subgroups in 2015-2016. Trends in underweight disparities were examined from 2005-2006 to 2015-2016. Multivariable-adjusted odds ratios (ORs; 95% confidence intervals, CIs) were calculated using logistic regression. Results: Approximately 11-22 million adults were included in each wave. In 2015-2016, the overall prevalence of underweight was 3.6% (men 2.0%, women 5.2%); severe underweight was 0.2% (men 0.1%, women 0.3%). The prevalence of underweight varied by sex and age groups. In men, those aged >= 80 years had the highest prevalence (overall 7.33%, severe underweight 0.84%). In women, those aged 20-29 years had the highest prevalence of overall underweight (14.57%), whereas those aged >= 80 years had the highest prevalence of severe underweight (1.38%). Compared with individuals in the lowest income quartile, men in the highest income had lower ORs of overall (0.59, 95% CI 0.59-0.60) and severe underweight (0.46, 95% CI 0.44-0.48); women in the highest income quartile had a higher OR of overall (1.12, 95% CI 1.12-1.13) but a lower OR of severe underweight (0.89, 95% CI 0.86-0.92). From 2005-2006 to 2015-2016, severe underweight consistently declined in older men but remained constant in women aged >= 80 years, widening sex disparities among older adults. Severe underweight decreased or leveled off in the highest income quartile but steadily increased in the lowest quartile, worsening income disparities. Conclusion: In this nationwide study, underweight was more prevalent among women, older adults aged >= 80 years, and low-income individuals. Disparities in severe underweight widened across sociodemographic subgroups over time. (c) 2024 The Authors. Published by SERDI Publisher. Elsevier Masson SAS. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).