25-Hydroxyvitamin D and blood pressure: a plateau effect in adults with African ancestry living at different latitudes
This study examined the association of 25-hydroxyvitamin D [25(OH)D] levels and blood pressure above and below 25(OH)D levels of 20 ng/ml in young adults with African ancestry.Methods:
This cross-sectional analysis utilized data from a pooled sample of 2242 adults with African ancestry from five different latitudes (403 in the United States, 474 in South Africa, 479 in Ghana, 448 in Jamaica, and 438 in Seychelles). Piecewise linear regression models with a single knot were fitted to determine above and below a 25(OH)D level of 20 ng/ml the slope of SBP and DBP while adjusting for covariates including calcium intake and site.Results:
The mean age was 34.4 (6.1) years, and 46.3% were men. Mean SBP and DBP were 118.1 (15.6) and 73.2 (12.2) mmHg, respectively, and were significantly higher among the United States vs Ghana, Jamaica, and Seychelles groups (P < 0.001 for all comparisons). 25(OH)D levels were significantly lower in the United States vs all other sites (P < 0.001 for all comparisons). When 25(OH)D levels were less than 20 ng/ml, slopes of SBP [−0.33 (95% confidence interval (CI) −0.57, −0.07)] and DBP [−0.21 (95% CI −0.40, −0.02)] were negative and significantly different from zero after adjustment for covariates. In contrast, with 25(OH)D levels above 20 ng/ml, the slopes of SBP [−0.03 (95% CI −0.13, 0.06)] and DBP [−0.04 (−0.11, 0.03)] did not differ significantly from zero.Conclusion
: The cross-sectional association of 25(OH)D with blood pressure is strongest when 25(OH)D levels are less than 20 ng/ml in young adults with African ancestry.