Association Between Vitamin D Intake and Sarcopenia in Older Adults in South Korea: The Moderating Role of the Area Deprivation Index

Sarcopenia contributes substantially to disability and mortality in older adults, and vitamin D plays an important role in muscle health. Using nationally representative data from the 2022 to 2023 Korea National Health and Nutrition Examination Survey (KNHANES), this study examined the association between dietary vitamin D intake and sarcopenia among adults aged ≥65 years and evaluated whether regional socioeconomic deprivation, measured by the Area Deprivation Index (ADI), moderates this relationship. Sarcopenia was defined using sex-specific cutoffs of appendicular skeletal muscle mass relative to body weight. Vitamin D intake was assessed using a 24-hour dietary recall, and ADI was constructed from regional socioeconomic indicators. Analyses accounted for the complex survey design and included multivariable and moderated logistic regression analyses. Higher vitamin D intake was associated with lower odds of sarcopenia, whereas higher ADI was associated with increased odds. A significant vitamin D intake × ADI interaction indicated that the protective association of vitamin D intake was attenuated in more socioeconomically deprived regions. These findings highlight the importance of incorporating regional socioeconomic context into nutrition policies and public health strategies aimed at preventing sarcopenia among older adults in South Korea.