Summary of studies exploring the relationship between serum levels of vitamin D and OSAS
| First author [ref.] | Comparison groups | Comments |
| Erden [29] | Non-OSAS controls versus moderate OSAS versus severe OSAS | Serum 25(OH)D levels were lower in both OSAS groups compared with control subjects and were negatively correlated with BMI and serum bisphenol A. |
| Salepci [30] | Non-OSAS controls versus mild OSAS versus moderate OSAS versus severe OSAS | Serum vitamin D levels were similar between patients with and without OSAS and between the various OSAS severity groups. There was no association between vitamin D levels and AHI, ODI or minimum O2 saturation. |
| Mete [31] | Non-OSAS controls versus mild OSAS versus moderate OSAS versus severe OSAS | Serum 25(OH)D levels were similar between OSAS and controls. The severe OSAS group had lower levels of 25(OH)D compared with other groups and the number of patients with serum 25(OH)D deficiency were higher in OSAS groups than in controls. |
| Barceló [32] | Mild OSAS versus moderate OSAS versus severe OSAS | Serum 25(OH)D levels were lower in severe compared with mild and moderate OSAS. Increased 25(OH)D levels decreased risk for diabetes and metabolic syndrome. |
| Bozkurt [33] | Non-OSAS controls versus mild OSAS versus moderate OSAS versus severe OSAS | Serum 25(OH)D levels were decreased in OSAS patients compared with control subjects and decrement was parallel to OSAS severity. Females with severe OSAS had significantly lower 25(OH)D levels compared with non-OSAS controls. |
| Piovezan [34] | Non-OSAS controls versus mild OSAS versus moderate OSAS versus severe OSAS | Moderate/severe OSAS and objective short sleep duration were associated with increased risk of 25(OH)D deficiency. |
| Archontogeorgis [35] | Non-OSAS controls versus OSAS patients | Serum 25(OH)D levels were lower in OSAS patients and were negatively correlated with sleep stages transitions, AHI, ODI and percentage of time with an oxyhaemoglobin saturation <90%, and positively correlated with average oxyhaemoglobin saturation. |
| Goswami [47] | Non-OSAS controls versus mild OSAS versus moderate OSAS versus severe OSAS | Subjects within the lowest 25(OH)D quartile were at increased risk of severe sleep apnoea compared with the highest 25(OH)D quartile. BMI and neck circumference were independent predictors of low serum 25(OH)D levels in OSAS. |
| Kerley [62] | Non-OSAS controls versus mild OSAS versus moderate OSAS versus severe OSAS | Serum 25(OH)D levels were higher in non-OSAS subjects and decreased with OSAS severity and were inversely correlated with BMI, % body fat, ODI, AHI, time spent below 90% O2 saturation and nocturnal heart rate. |
| Toujani [63] | Non-OSAS controls versus severe OSAS | Serum vitamin D levels were negatively correlated with nocturia severity and IL-17, and positively correlated with mean O2 saturation and minimum O2 saturation. |
BMI: body mass index; ODI: oxygen desaturation index.