Associations of 25-Hydroxyvitamin D Levels and Arthritis with Sleep Duration: The Korean National Health and Nutrition Examination Survey 2008-2014

Purpose: The mean sleep duration of Koreans is 7 hours 49 minutes, which is the lowest among Organization for Economic Cooperation and Development countries. Although vitamin D deficiency and arthritis are considered modifiable factors influencing restorative sleep, mean vitamin D levels are low (17.33 ng/mL) and arthritis is prevalent among Koreans. This study investigated whether vitamin D deficiency and arthritis increase the risk of short sleep duration. Patients and Methods: The current study used data from the Korean National Health and Nutrition Examination Survey (KNHANES) for 46,405 Korean adults. Vitamin D levels were measured using a radioimmunoassay kit. Sleep duration and arthritis history were assessed using a self-reported questionnaire. Sleep duration was categorized as optimal (7 to <9 hours/day), short (<7 hours/day), and long (>= 9 hours/day). Vitamin D levels were grouped as vitamin D sufficiency (>= 20 ng/mL), insufficiency (10-19.99 ng/mL), and deficiency (<10 ng/mL). Multiple imputation was used to compensate for missing data. Multinomial logistic regression was used to examine the associations of vitamin D and arthritis status with sleep duration. The regressions were adjusted for covariates, and each model was adjusted for vitamin D and arthritis. Results: Among these participants, 23,078 (49.73%) and 3518 (7.58%) had short and long sleep duration, respectively; 26,724 (57.59%) and 4349 (9.37%) exhibited vitamin D insufficiency and deficiency, respectively; and 4709 (10.15%) were arthritis patients. Compared with vitamin D sufficiency, vitamin D insufficiency and deficiency were associated with short sleep duration (vitamin D insufficiency group: OR = 1.07, 95% CI = 1.01-1.13; vitamin D deficiency group: OR = 1.13, 95% CI = 1.03-1.24). The presence of arthritis was associated with short sleep duration (OR = 1.14, 95% CI = 1.06-1.22) compared with its absence. The interaction between vitamin D deficiency and the presence of arthritis was significantly associated with short sleep duration. However, long sleep duration was not significantly associated with vitamin D levels or arthritis status. Conclusion: Low vitamin D levels and the presence of arthritis were associated with an increased risk of short sleep duration. Additionally, there was a positive interaction effect between vitamin D deficiency and arthritis on short sleep duration.