July 1, 2019 -- A prospective birth cohort study has linked low vitamin D levels in pregnant women and babies with the development of high blood pressure in childhood, researchers reported in Hypertension on July 1. The group called for screening to flag and correct deficiencies.
Newborns who had low vitamin D levels had a 60% higher risk of developing elevated systolic blood pressure (SBP) between the ages of 6 and 18 years, compared with those who had normal vitamin D levels. The cohort of 775 children were seen at Boston Medical Center as part of the Children's Health Study, which is being supported by the U.S. National Institutes of Health and the U.S. Department of Health and Human Services.
In addition, those with persistent low vitamin D through early childhood were twice as likely to have elevated systolic blood pressure between the ages of 3 and 18 years, reported Dr. Guoying Wang, PhD, an assistant scientist at the Johns Hopkins Bloomberg School of Public Health, and colleagues.
The study provides evidence for prenatal and postnatal vitamin D supplementation along with other lifestyle changes to prevent elevated systolic blood pressure in childhood, the authors suggested.
"Screening for vitamin D levels during pregnancy or the first years of life should be recommended for pregnant women and their babies who are at a high risk, such as those with cardiometabolic risk conditions, so that they receive appropriate treatment and monitoring," the authors wrote. "Our work underscores that the perinatal and early childhood periods are critical windows for nutritional interventions aimed at preventing the development of hypertension in late life."
Tracing roots of cardiovascular conditions
The Boston study reflects active research into the potential role of vitamin D for preventing cardiovascular disease (CVD), as well as a wide range of other conditions. There is a mechanistic rationale for vitamin D in cardiovascular event prevention due to its role in regulating the renin-angiotensin system, among other things.
However, in June, a large meta-analysis found that contrary to conventional wisdom, vitamin D did not help prevent cardiovascular events, spurring more discussion about appropriate cutoff points for tests and whether low vitamin D causes cardiovascular events or is just associated with them.
The Hypertension study just reported was designed to elucidate the link between low vitamin D at birth and elevated blood pressure years later.
"Although a causal link between prenatal low vitamin D and SBP has not yet been established, it is possible that variations in prenatal vitamin D exposure programs fetal development and influences arterial structure and metabolic processes that affect future cardiovascular health," Wang et al wrote.
Nutrition early in life is associated with the development of high blood pressure and cardiovascular disease later, and vitamin D is an important nutrient for fetal development, the researchers noted.
"Even more important, vitamin D deficiency and insufficiency are now highly prevalent worldwide, in particular, among pregnant women and children," they wrote. "Because fetal circulating vitamin D concentrations are primarily dependent on maternal status, vitamin D deficiency in the fetus has also become a public health issue."
Vitamin D deficiency was common
The rise of childhood obesity has brought a rise in elevated blood pressure in children, and consequently, prevention guidelines recommend measuring blood pressure in kids starting at age 3, according to the authors. Systolic blood pressure has been associated with cardiovascular outcomes, and elevated blood pressure was defined in the study as being in the top 25% based on rates in the overall population.
The researchers enrolled children between 2005 and 2012; there was a greater representation of children who were black -- 531 of the total -- and who were from low income, urban households.
Vitamin D tests typically measure 25-hydroxyvitamin D, or 25-OH D. Wang and colleagues defined low vitamin D status as a plasma 25-OH D level less than 11 ng/mL in umbilical cord blood and less than 25 ng/mL in early childhood, based on results from a liquid chromatography-tandem mass spectrometry assay.
"Using this cut point, the prevalence of vitamin D deficiency in our cohort (44.3% at birth and 23.0% in early childhood) was substantial, but consistent with that reported in other epidemiological studies," they wrote.
Low vitamin D was associated with elevated systolic blood pressure "above and beyond established hypertension risk factors." Subjects with mothers who had cardiometabolic conditions were at particularly high risk.
"Our findings highlight that both prenatal and early childhood vitamin D levels appear to play a substantial role in the development of elevated [systolic blood pressure], especially among those born to mothers with obesity, diabetes mellitus, or hypertensive disorders," Wang and colleagues wrote.
The study shows that low vitamin D adds to the negative effects of mothers' cardiometabolic conditions on systolic blood pressure in children, and that boosting levels of the nutrient may reduce the number of cardiovascular events across generations, they suggested.
"Further clinical and experimental studies may be warranted to validate our findings," the authors concluded. "If our findings are confirmed, prenatal and early childhood screening and optimal vitamin D supplementation may form a cost-effective approach to reduce the risk of hypertension and CVD later in life, given the safe and low cost of treating vitamin D deficiency, especially in black or obese populations."