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Vitamin D deficiency ‘increases hypertension risk’
19 November 2008
MedWire News: Young women with low plasma levels of vitamin D are at increased risk for developing hypertension, researchers have shown.
They say that if the association is causal then a substantial proportion of hypertension in young women could be attributed to suboptimal levels of 25-hydroxyvitamin D [25(OH)D] – and potentially be amenable to intervention.
For the study, John Forman (Harvard Medical School, Boston, Massachusetts, USA) and colleagues studied 1482 normotensive women aged 32–52 years. The women were participating in the Nurses’ Health Study II, an ongoing prospective cohort study.
Forman et al used a nested case–control design to match women who developed incident hypertension during follow-up with those who did not. The pairs were matched for age, race, and month of blood collection and further adjusted for body mass index, physical activity, family history of hypertension, oral contraceptive use, and blood parameters.
Median plasma 25(OH)D levels were lower in cases than in controls (25.6 vs 27.3 ng/ml, p<0.001), Forman and colleagues report in the journal Hypertension.
Women in the lowest quartile of plasma 25(OH)D were 66% more likely to develop hypertension than were those in the highest quartile (p for trend=0.01).
After multivariate adjustment, women with vitamin D deficiency (<30 ng/ml) were 47% more likely to develop hypertension compared with women with sufficient levels.
Finally, when plasma 25(OH)D was examined as a continuous variable, every 5-ng/ml lower 25(OH)D level was associated with an adjusted odds ratio for incident hypertension of 1.08; this rose to 1.11 among women with vitamin D deficiency.
Forman and team note that nearly two-thirds of this apparently healthy study population was deficient in vitamin D at baseline, meaning the results have substantial public health implications.
“If this association is causal, then vitamin D deficiency may account for 23.7% of all new cases of hypertension among young women every year,” they write.
“Our findings should be tested in randomized trials to determine whether vitamin D supplementation could be effective in reducing blood pressure.”
