Repletion of vitamin D associated with deterioration of sleep quality among postmenopausal women

Reduced health-related quality of life (HRQOL), depressive symptoms and poor sleep quality are important health issues among postmenopausal women and may be associated with low vitamin D status. Overweight postmenopausal women, with serum 25-hydroxyvitamin D [25(OH)D] 10-32 ng/m, were recruited in Seattle, WA (2010 − 2012) and randomly assigned to 12 months of weight loss + 2000 IU oral vitamin D3/day or weight loss + daily placebo. The weight-loss program included a reduced-calorie diet and 225 min/week of moderate-to-vigorous aerobic activity. Eight subscales of HRQOL were assessed by the MOS 36-Item Short-Form Health Survey. Depressive symptoms were assessed using the Brief Symptom Inventory-18, and sleep quality was assessed using the Pittsburg Sleep Quality Index (PSQI). Mean 12-month changes in HRQOL, depressive symptoms and sleep quality were compared between groups (intent-to-treat) using generalized estimating equations. Compared to placebo, women receiving vitamin D did not experience any significant change in depressive symptoms (p = 0.78), HRQOL subscales (all p > 0.05), or overall sleep quality (p = 0.21). However, a greater magnitude of change in serum 25(OH)D was associated with an increased need to take medications to sleep (ptrend = 0.01) and overall worse sleep quality (ptrend < 0.01). Women who became vitamin D replete (≥ 32 ng/mL) also showed a deterioration in total PSQI sleep quality score compared to women who remained < 32 ng/mL despite supplementation, even after adjusting for relevant covariates (Non-Replete: − 5.7% vs. Replete: + 6.2%, p < 0.01). Vitamin D supplementation of 2000 IU/d may result in overall worse sleep quality for postmenopausal women with low circulating vitamin D undergoing weight loss.