NEW YORK (Reuters Health) – Premenopausal women with vitamin D deficiency are at increased risk for systolic hypertension in the coming years, according to study findings presented Thursday at the American Heart Association’s 63rd High Blood Pressure Research Conference in Chicago.

“The take home message for clinicians and the general public is that low levels of vitamin D in young adulthood may put women at heightened risk for hypertension at mid-life,” lead researcher Flojaune C. Griffin, from the University of Michigan, Ann Arbor, told Reuters Health.

Griffin said that several prior studies have yielded similar findings. The present study, however, “is novel because it has a longer follow up than most other comparable studies, examines women in early adulthood at baseline and follows them through mid-life, and uses the current definition of vitamin D deficiency which is based on evidence from studies of other health outcomes,” she noted.

The results stem from an analysis of data for 559 Caucasian women who were enrolled in the population-based longitudinal Michigan Bone Health and Metabolism Study. The women were 24 to 44 years of age when blood pressure measurements and data collection began in 1992. Vitamin D levels were measured in 1993 and compared with blood pressure measurements taken that year and again in 2007.

Vitamin D (25-OH-D) deficiency was defined as a serum level of less than 80 nmol/L, which is higher than the thresholds used in most previous studies, Griffin said. “Misclassification of vitamin D status can lead to an underestimation of its importance,” Griffin added.

Overall, 81% of women were vitamin D deficient in 1993. In 2007, hypertension was diagnosed in 19% of women.

On cross-sectional analysis, women with vitamin D deficiency were more likely than those without it to also have systolic hypertension, but the association was not statistically significant (OR = 1.1). By contrast, in the prospective analysis, vitamin D deficiency in 1993 was significantly linked to systolic hypertension in 2007 with a risk ratio of 3.0 after adjusting for age, fat mass, anti-hypertensive drug use, and smoking.

Vitamin D status was not significantly associated with diastolic hypertension in either analysis, the researchers found.

“Because this study was conducted in a Caucasian population, what remains to be answered is how the prospective association between vitamin D and blood pressure is influenced by melanin–the primary determinant of skin color,” Griffin said, noting that her team is now conducting a study examining this. “Additionally, because vitamin D was only measured at baseline, we are unaware of how changes in vitamin D over the follow up period vary with blood pressure.”