Background Both vitamin D deficiency and hypertension are increasingly prevalent public health concerns in developing countries.
Objectives This study aims to assess 25-hydroxyvitamin D (25(OH)D) status in postmenopausal women and to analyze its relationships with arterial hypertension.
Methods A total of 200 tunisian postmenopausal women aged from 50 to 89 years were recruited from the rheumatology departement in CHU Hedi Chaker, Sfax, Tunisia.
Clinical characteristics and patient medical history were collected using a validated questionnaire. Blood samples were taken for measurements of vitamin D, intact parathyroid hormone (PTH), and routine chemical analysis.
Serum 25(OH)D and PTH were measured by electrochemiluminescence.
SPSS 20 was used for the statistical analysis.
Results The mean age was 63,74 ± 7,8 years. Mean PTH was 61,80 ± 25,6 ng/L.
Serum 25(OH)D levels were below 10, 20, and 30 ng/ml in 55, 30.5 and 14.5% of participants, respectively. Systolic blood pressure (SBP) was above 140mmHg in 60,5% of the patients while 26.5% had a diastolic blood pressure (DBP) higher than 90mmHg. PTH was highly correlated to 25(OH)D (r=-0,305, p<0,001) but not to the blood pressure levels. Serum 25(OH)D levels were negatively correlated to SBP (r=-0,121, p=0,045) and to HBP(r=-0,163, p=0,021).
After multivariate adjustment for a range of potential covariates (Age, Body mass index, waist size and glomerular filtration rate) in a binary logistic regression model, a significant inverse association was found between serum 25(OH)D concentration and systolic hypertension risk: In fact Risk of systolic hypertension seems to be lowered in the group with high 25(OH)D levels (≥15 ng/mL) compared with those with low levels (<15 ng/mL) (adjusted OR=0,512, CI 0.270–0.972), p=0,03). However, we have not noted a significant association between vitamin D levels and the risk of systolic hypertension (adjusted OR=1.01, 95% CI=0.495–2.064, p=0,97).
Conclusions This study is timely, because a discrepancy exists between findings from observational studies and results of randomized intervention trials.
Reverse causation, inherent weakness of observational studies, is a possible explanation as individuals with hypertension might have more chronic diseases and therefore spend less time outdoors with sun exposure, important for endogenous vitamin D production.
In fact, randomized intervention trials will be needed to determine whether vitamin D supplementation can be used to prevent or treat hypertension.
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Tamez H, Thadhani RI. Vitamin D and hypertension: an update and review. Curr Opin Nephrol Hypertens 2012; 21: 492–99.
Disclosure of Interest None declared