Black American women with low levels of vitamin D appeared are at increased incidence of COVID-19 infection, found research led by Boston University’s Slone Epidemiology Center.
Researchers from assessed levels of vitamin D (deficient, insufficient and sufficient) among women who had been tested for COVID-19 using data from the Black Women’s Health Study (BWHS), a prospective cohort study established in 1995, when 59,000 black women ages 21 through to 69 years enrolled by completing health questionnaires. These findings appear online in the journal PLOS ONE.
The study estimated that black American women with deficient levels of vitamin D had a 69% greater risk of COVID-19 infection than women with sufficient vitamin D levels. The association between low serum vitamin D and higher risk of infection was strongest among women with obesity, an important finding given the higher prevalence of obesity among black women compared with other American women.
A few other studies have reported inverse associations between vitamin D and COVID-19 infection, but these were largely in whites or did not provide estimates according to either race or BMI. As the first published analysis on the relation of serum vitamin D and COVID-19 infection in black women, these findings may help to explain why black women are overrepresented among COVID-19 cases, as this population commonly experiences vitamin D insufficiency.
The study also shows that a number of important factors related to risk of COVID-19 infection, including number of people in the household, years of education and residential neighbourhood socioeconomic status, did not account for the association.
It is widely known that vitamin D deficiency and obesity are associated with risk of chronic diseases like osteoporosis, cancer, and cardiovascular disease. These findings add COVID-19 to that list.
“Nearly one out of four people has vitamin D blood levels that are too low or inadequate for bone and overall health,” says lead author Yvette Cozier, DSc, associate professor of epidemiology at Boston University School of Public Health and an investigator on the Black Women’s Health Study at BU’s Slone Epidemiology Center.
“Our study provides another reason why adequate levels of vitamin D are important – the possibility of lowering risk of COVID-19 infection.”
Clinical trials now are under way to determine whether vitamin D helps reduce the risk of COVID-19 or helps reduce symptoms in people who have COVID-19, but results are not yet available.
Further research is needed to confirm these findings and determine the optimal level of vitamin D for a beneficial effect against COVID-19.
Study details
Lower serum 25(OH)D levels associated with higher risk of COVID-19 infection in US black women
Yvette C. Cozier, Nelsy Castro-Webb, Natasha S. Hochberg, Lynn Rosenberg, Michelle A. Albert, Julie R. Palmer
Published in PLOS ONE 27 July 2021
Abstract
Objective
Limited evidence suggests that higher levels of serum vitamin D (25(OH)D) protect against SARS-CoV-2 virus (COVID-19) infection. Black women commonly experience 25(OH)D insufficiency and are overrepresented among COVID-19 cases. We conducted a prospective analysis of serum 25(OH)D levels in relation to COVID-19 infection among participants in the Black Women’s Health Study.
Methods
Since 1995, the Black Women’s Health Study has followed 59,000 US black women through biennial mailed or online questionnaires. Over 13,000 study participants provided a blood sample in 2013–2017. 25(OH)D assays were performed in a certified national laboratory shortly after collection of the samples. In 2020, participants who had completed the online version of the 2019 biennial health questionnaire were invited to complete a supplemental online questionnaire assessing their experiences related to the COVID-19 pandemic, including whether they had been tested for COVID-19 infection and the result of the test. We used logistic regression analysis to estimate odds ratios (OR) and 95% confidence intervals (CI) for the association of 25(OH)D level with COVID-19 positivity, adjusting for age, number of people living in the household, neighbourhood socioeconomic status, and other potential confounders.
Results
Among 5,081 eligible participants whose blood sample had been assayed for 25(OH)D, 1,974 reported having had a COVID-19 test in 2020. Relative to women with 25(OH)D levels of 30 ng/mL (75 nmol/l) or more, multivariable-adjusted ORs for COVID-19 infection in women with levels of 20–29 ng/mL (50–72.5 nmol/l) and <20 ng/mL (<50 nmol/l) were, respectively, 1.48 (95% CI 0.95–2.30) and 1.69 (95% CI 1.04–2.72) (p trend 0.02).
Conclusion
The present results suggest that US black women with lower levels of 25(OH)D are at increased risk of infection with COVID-19. Further work is needed to confirm these findings and determine the optimal level of 25(OH)D for a beneficial effect.
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