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

purposeThe 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

methodsThe 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.

resultsAmong 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.

conclusionLow 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.