25-Hydroxyvitamin D and ankle-brachial blood pressure index in adults without peripheral artery disease

Background: Inverse association between lower level of 25-hydroxyvitamin D [25(OH)D] and higher prevalence of peripheral arterial disease (PAD) among individuals with cardiovascular diseases (CVD) is known. Less is known about the relationship between 25(OH)D and ankle-brachial blood pressure index (ABPI) in asymptomatic adults. We hypothesized a nonlinear relationship between 25(OH)D and ABPI in asymptomatic adults without PAD. Methods: Data from the continuous NHANES (2001-2004) was used. Minimum of the two reported ABPI value was chosen for each individual (>18 years). Linear regression models with spline adjusted for demographic and traditional risk factors for CVD were used to examine nonlinear relationship between 25(OH)D and ABPI. Mean changes in ABPI per 10 ng/mL change in 25(OH)D were reported. Results: Mean (SD) age and 25(OH)D levels of 4979 participants (48% females) were 60.4 (13.22) years and 22.1 (8.68) ng/mL, respectively, while mean (SD) ABPI was 1.07 (0.15). We observed positive association between 25(OH)D and ABPI both in the univariable and multivariable regression models (all p < 0.05). In univariable regression with spline, a significant increase in ABPI (ß = 0.03, 95% CI: 0.02-0.04) was observed until 25(OH)D reached but not above 27 ng/mL. Similarly, in multivariable spline models, 25(OH)D was positively associated with ABPI (ß = 0.02, 95% CI: 0.01-0.03) only up to 27 ng/mL. Conclusions: In asymptomatic adults without PAD, rising serum 25(OH)D concentration but not above 27 ng/mL was associated with statistically significant increase in ABPI.