Relationships of the Vitamin D and Platelet Indices in Sjögren’s Syndrome

Vitamin D and Sjögren's Disease: Revealing the Connections-A Systematic Review and Meta-Analysis

BACKGROUND

The aim of the present review was to summarize the current evidence about the impact of vitamin D deficiency on pathology and clinical manifestations of Sjögren's disease (SD).

METHODS

Databases PubMed, Web of Science, Scopus, and Cochrane library were searched for studies assessing the levels of vitamin D in SD patients using the following keywords: (vitamin D OR calciferol OR cholecalciferol OR 25-hydroxyvitamin D OR 25-hydroxycholecalciferol OR calcidiol OR calcitriol OR 1,25-dihydroxycholecalciferol) AND (Sjögren's Syndrome OR Sjögren's disease) accessed on 20 September 2022. Out of 248 retrieved studies, following the systematic review methodology and defined inclusion and exclusion criteria, 9 clinical studies were eligible to be included in the present review: 4 of them case-control, 4 cross-sectional, and 1 cohort study.

RESULTS

Nine studies totaling 670 SD patients and 857 healthy controls were eligible for meta-analysis with moderate to high methodological quality as determined by the Newcastle-Ottawa Quality Scale (NOS). According to the obtained results, a high prevalence of hypovitaminosis D was observed in SD patients when compared to healthy controls (95% CI -10.43, -2.39; p < 0.01).

CONCLUSION

Available evidence points to lower levels of vitamin D in patients with SD in comparison to healthy controls. However, further studies are necessary to understand the underlying mechanisms associated with the role of vitamin D in the development and disease severity of SD.

Hydroxyvitamin D Serum Levels are Negatively Associated with Platelet Number in a Cohort of Subjects Affected by Overweight and Obesity

BACKGROUND

Hypovitaminosis D and higher platelet numbers are emerging as cardiovascular risk factors, in particular in obese subjects.

METHODS

This observational study was aimed at investigating the relationship between platelet number and serum 25-hydroxyvitamin D (25(OH)D) levels in a cohort of individuals affected by overweight and obesity (body mass index (BMI) ≥ 25 Kg/m²). A sample of 341 subjects (248 women, 93 men), aged 18-71 years, taking no medication, was examined. Anthropometric, hormone, metabolic and common routine hematochemical parameters were examined and evaluated in association with platelet count and serum 25(OH)D levels.

RESULTS

Platelet numbers were inversely related to age (p < 0.04), 25(OH)D (p < 0.05) and uric acid (p < 0.04) levels, and directly associated with white blood cells (p < 0.01), Thyroid Stimulating Hormone (TSH) (p < 0.04), insulin levels (p < 0.002) and Homeostasis Model Assessment - Insulin Resistance (HOMA-IR) (p < 0.002). We applied statistical regression models to examine the relationship between platelet count (dependent variable) and parameters that had univariate associations with platelet numbers, showing that the association between platelet count and 25(OH)D was not confirmed. Moreover, vitamin D showed a negative independent association with BMI, diastolic blood pressure and serum insulin levels.

CONCLUSIONS

This study indicates, for the first time, that vitamin D deficiency is associated with a parallel increase in platelet number, suggesting that higher platelet numbers may be one of the possible mechanisms leading to a greater cardiovascular risk in obese subjects. It also shows that vitamin D deficiency, a common condition in obesity, has independent associations with higher BMI, diastolic blood pressure and serum insulin levels.