Vitamin D status and its correlation with blood pressure and plasma renin level in pre-menopausal Saudi women: A cross-sectional study

Abstract

BACKGROUND AND OBJECTIVES: Vitamin D deficiency is a major health problem in the Saudi population. A negative association between blood pressure and 25(OH)D level had been suggested in several clinical and epidemiological studies and evidence for an effect of 25(OH)D in lowering blood pressure was reported. Subsequent experimental work showed that 1,25(OH)2D3 inhibits renin gene expression. These findings indicate that 1,25(OH)2D3 deficiency may play a role in the pathogenesis of hypertension through its effect on the renin-angiotensin system and that correction of vitamin D deficiency may prevent or reduce the cardiovascular risk associated with hypertension. There are no studies on the relationship between blood pressure or renin concentration and vitamin D status in the Saudi population. Therefore, the aims of this study were to 1) investigate the effect of poor vitamin D status on blood pressure level in Saudi women and 2) to determine the association between vitamin D level and plasma renin concentration. SUBJECTS AND METHODS: The study population included 201 healthy Saudi premenopausal females (20-45 years old) attending center of excellence for osteoporosis research (CEOR) for a study on the assessment of bone health in the Saudi population. Blood pressure was measured by a standardized method using an automated blood pressure monitor (BPTru) that has been validated by the British Hypertension Society (BHS). Fasting blood samples were collected from each participant after 20 minutes of rest in the seated position. Serum 25 hydroxyvitamin D, parathyroid hormone and renin concentration were measured by sandwich chemiluminescence immunoassay method (DiaSorin, MN, USA). RESULTS: The analysis included 192 subjects who were normotensive (blood pressure <140/90 mmHg). A total of 34% of women had severe vitamin D deficiency (25(OH)D ≤ 12.5 nmol/L); 41% had moderate deficiency (25(OH)D levels between 12.5 - 25 nmol/L); 23% had mild deficiency (25(OH)D level ≥ 25 - < 50 nmol/L); and 2% had insufficiency (25(OH)D level ≥ 50 - ≤ 75 nmol/L). None had a sufficient level of ≥75 nmol/L. The systolic blood pressure ranged from 79-130.5mmHg and the diastolic from 48.5-85.5 mmHg. Both systolic and diastolic blood pressures were significantly higher in women that were in the lower 2 quartiles of vitamin D. However, linear regression analysis adjusting for potential confounders showed that 25(OH)D level was not a predictor of either systolic or diastolic blood pressures. There was a significant negative correlation between 25(OH)D and Diastolic blood pressure. A negative correlation (although not significant) was found between vitamin D level and plasma renin concentration in this study group. CONCLUSION: Vitamin D deficiency was highly prevalent among the study group. Vitamin D was not a predictor of either systolic or diastolic blood pressure. There was a negative correlation between vitamin D level and renin concentration although not statistically significant. It is possible that any underlying relationship was obscured by the relatively young age group or due to the narrow blood pressure range of the studied population. A larger sample size including hypertensive subjects may be needed.