Abstract
Background/objectivesThere is evidence of black–white differences in vitamin D status and cardiometabolic health. This study aimed to further evaluate the joint associations of 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH) with risks of diabetes and related cardiometabolic comorbidities among white and black women.Subjects/methodsWe cross-sectionally and prospectively analyzed data from 1850 black and 3000 white postmenopausal women without cardiovascular disease or dialysis at baseline from the Women’s Health Initiative—Observational Study. Weighted Cox proportional hazards analyses and weighted logistic regression models were used to examine the joint associations of 25(OH)D and PTH with incident diabetes and prevalence of other diabetes-related cardiometabolic comorbidities (including CKD, hypertension, or obesity).ResultsWe identified 3322 cases of obesity (n = 1629), hypertension (n = 2759), or CKD (n = 318) at baseline and 453 incident cases of diabetes during 11 years of follow-up. Cross-sectionally, lower 25(OH)D and higher PTH were independently associated with higher prevalence of hypertension [odds ratio (OR) = 0.79; 95% confidence interval (CI): 0.72–0.87 and OR = 1.55; 95% CI: 1.39–1.73] among white women only. When stratified by diabetes status, compared to women with 25(OH)D ≥50 nmol/L and PTH ≤6.89 pmol/L (65 pg/mL), women who did not have diabetes with vitamin D deficiency (<50 nmol/L) and PTH excess (>6.89 pmol/L) had higher prevalence of CKD, hypertension, or obesity (OR = 4.23; 95% CI: 2.90–6.18) than women who had diabetes (OR = 1.89; 95% CI: 0.96–3.71). Prospectively, lower 25(OH)D was associated with lower diabetes incidence [hazard ratio (HR) = 0.73; 95% CI: 0.62–0.86] in white women. Jointly, compared to the group with 25(OH)D ≥50 nmol/L and PTH ≤6.89 pmol/L, white women with 25(OH)D deficiency (<50 nmol/L) had elevated risk for diabetes, regardless of PTH levels.ConclusionsLow 25(OH)D and high PTH were jointly associated with increased risk of diabetes among white women only. Their joint associations with high prevalence of CKD, hypertension, and obesity were more pronounced among women without diabetes.
Highlights
There is consistent evidence that black Americans tend to have lower total 25-hydroxy vitamin D [25(OH)D] levels than white Americans, potentially due to reduced cutaneous biosynthesis of vitamin D [1, 2]
In line with our findings, a prospective study of 494 postpartum women in Canada suggested that vitamin D deficiency/insufficiency with parathyroid hormone (PTH) in the highest tertile at 3 months postpartum was associated with worsening β-cell function and insulin sensitivity and increased fasting and 2-h glucose 9 months later, after controlling for age, ethnicity, family history of type 2 diabetes, previous gestational diabetes, body mass index (BMI), glucose, duration of breast-feeding, physical activity, and season of blood draw [21]
Our results indicate that the combined associations of deficient vitamin D and elevated PTH with the aforementioned cardiometabolic conditions may vary depending on diabetes status
Summary
There is consistent evidence that black Americans tend to have lower total 25-hydroxy vitamin D [25(OH)D] levels than white Americans, potentially due to reduced cutaneous biosynthesis of vitamin D [1, 2]. To take into account the sampling strategies (different subcohort sampling fractions were used for selecting controls and incident cases among white women and black women) used in the case–cohort study, we compared the weighted distributions of each vitamin D biomarker stratified by status of diabetes at baseline between white and black women, as well as between women with and without any diabetes-related cardiometabolic comorbidity. PTH, creatinine, high- vitamin D biomarkers with diabetes-related cardiometabolic comorbidities sensitivity C-reactive protein (hs-CRP), fasting glucose, and fasting insulin at baseline, weighted logistic regression models of women with and were measured by an electrochemiluminescence immunoassay on the without prevalent or incident diabetes among all participants and each. We observed that the interaction between race/ethnicity and diabetes-related cardio-
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