Association Between Self‐Reported Sleep Duration and Serum Vitamin D Level in Elderly Korean Adults

Objectives To investigate the association between self‐reported sleep duration and serum vitamin D level in elderly K orean adults. Design Cross‐sectional data analysis. Setting K orean N ational H ealth and N utrition E xamination S urvey 2010. Participants Noninstitutionalized adults aged 60 to 80 (N = 1,614). Measurements The confounding variables were serum 25‐hydroxy vitamin D level, age, sex, body mass index, smoking history, alcohol consumption, and self‐reported daily sun exposure and sleep duration. Self‐reported daily sleep duration was divided into four groups: Q1 (≤4 hours), Q2 (5–6 hours), Q3 (7–8 hours), and Q4 (≥9 hours). Results Mean serum vitamin D levels of subjects in the Q1, Q2, Q3, and Q4 groups were 44.18, 48.08, 48.83, and 51.78 nmol/L, respectively. On multivariate linear regression analysis, subjects in the Q2 ( B  = 3.80, 95% confidence interval ( CI ) = 0.42–7.19), Q3 ( B  = 4.89, 95% CI  = 1.54–8.24), and Q4 ( B  = 5.18, 95% CI  = 0.78–9.58) groups had significantly higher serum vitamin D levels than subjects in the Q1 group. Conclusion Serum vitamin D level is positively associated with self‐reported daily sleep duration in elderly Korean individuals. These results suggest that inadequate sleep duration may be associated with lower vitamin D levels in elderly adults.