Vitamin D, race, and excessive daytime sleepiness

Abstract

Study objectives: First, to determine whether serum vitamin D levels were correlated with excessive daytime sleepiness (EDS) in patients with or without vitamin D deficiency (VitDd). Second, to assess whether race affected the relation between vitamin D levels and EDS.

Methods: Serum 25-hydroxyvitamin D (25OHD) was measured by immunoassay in a consecutive series of 81 sleep clinic patients who complained of sleep problems and nonspecific pain (25OHD < 20 ng/mL ' VitDd). Sleepiness was determined using the Epworth Sleepiness Scale score ([ESSs] ESSs ≥ 10 ≡ EDS). Correlations were assessed using Pearson r.

Results: In patients without VitDd (25OHD ≥ 20 ng/mL), ESSs was inversely correlated with vitamin D concentration (r = 0.45, p < 0.05). The group consisted of 6% black patients, compared with 35% for the entire cohort. Among the patients who had VitDd (25OHD < 20 ng/mL), ESSs was directly correlated with 25OHD in black (r = 0.48, p < 0.05) but not white patients. In black patients, mean ESSs in patients with VitDd were higher and 25OHD levels were lower p < 0.05).

Conclusions: The results suggested the novel possibility that VitDd-related disease has a yet-to-be-identified mechanistic role in the presentation of sleepiness, sleep disorders, or both. Further research is needed to clarify the mechanism(s) involved in producing the complex relationships noted.

Figure 1. Epworth Sleepiness Scale score (ESSs) as a function of vitamin D concentration in patients without vitamin D deficiency (25OHD ≥ 20 ng/mL)

Figure 2. Epworth Sleepiness Scale score (ESSs) as a function of vitamin D concentration in patients with vitamin D deficiency (25OHD < 20 ng/mL)

(A) Individual patients stratified by race. Black patients, r = 0.48 (p < 0.05). White patients (dashed line), r = −0.27 (NS). (B) Mean sleepiness ± SD. *p < 0.05.