Association Between Physical Activity Levels and Chronic Disease Risk Among Korean Adults with Sleep Deficiency

Background/Objectives: This study investigated the association between physical activity (PA) levels and the risk of chronic diseases in Korean adults with sleep deficiency (SD). Methods: Data were obtained from the Korea National Health and Nutrition Examination Survey (2016–2021; n = 31,338). SD was defined as less than 7 h of sleep per night. The PA levels were categorized as low, moderate, or high. Multivariable logistic regression was used to estimate odds ratios (OR) with 95% confidence intervals (CI) for various chronic diseases, adjusting for demographic and lifestyle covariates. Results: High PA levels were associated with lower odds of abdominal obesity (OR = 0.855, 95% CI = 0.782–0.934, p < 0.001), hypertension (OR = 0.787, 95% CI = 0.657–0.942, p < 0.01), diabetes mellitus (OR = 0.743, 95% CI = 0.622–0.887, p < 0.01), and metabolic syndrome (OR = 0.706, 95% CI = 0.586–0.850, p < 0.001). Moderate PA showed similar but weaker associations. Conversely, high PA levels were associated with higher odds of depression (OR = 1.474, 95% CI = 1.123–1.935, p < 0.01). Subgroup analyses indicated that the protective effects of PA were stronger among women, non-smokers, and individuals with obesity. Conclusions: Among adults with SD, moderate-to-vigorous PA is associated with a lower odds of several metabolic disorders, including abdominal obesity, diabetes, and metabolic syndrome. This highlights the importance of regular PA in maintaining metabolic health. However, a positive association between high PA and depression should warrant further investigation, as reverse causality or residual confounding may explain this association.