Serum 25-Hydroxyvitamin D3 and Mammography Density among Mexican Women

Abstract

Low circulating levels of vitamin D and high mammographic density (MD) have been associated with higher risk of breast cancer. Although some evidence suggested an inverse association between circulating vitamin D and MD, no studies have investigated this association among Mexican women. We examined whether serum 25-hydroxyvitamin D3 [25(OH)D3] levels were associated with MD in a cross-sectional study nested within the large Mexican Teacher's Cohort. This study included 491 premenopausal women with a mean age of 42.9 years. Serum 25(OH)D3 levels were measured by liquid chromatography/tandem mass spectrometry. Linear regression and non-linear adjusted models were used to estimate the association of MD with serum 25(OH)D3. Median serum 25(OH)D3 level was 27.3 (23.3-32.8) (ng/ml). Forty one (8%) women had 25(OH)D3 levels in the deficient range (< 20 ng/ml). Body mass index (BMI) and total physical activity were significantly correlated with 25(OH)D3 (r = -0.109, P = 0.019 and r = 0.095, P = 0.003, respectively). In the multivariable linear regression, no significant association was observed between 25(OH)D3 levels and MD overall. However, in stratified analyses, higher serum 25(OH)D3 levels (≥27.3 ng/ml) were significantly inversely associated with percent MD among women with BMI below the median (β = -0.52, P = 0.047). Although no significant association was observed between serum 25(OH)D3 and percent MD in the overall population, specific subgroups of women may benefit from higher serum 25(OH)D3 levels.

Fig 1. Association of serum 25(OH)D3 and percent MD, stratified by BMI.

Based on population distribution, the quartiles (25th percentile, 50th percentile, 75th percentile) of percent MD that divide the MD set into four equal group were estimated (MD ≤ 22.6%, 22.6–37.7%,; 37.5–51.9%, and > 51.9%). A subset of women was selected based on whether they had low percent MD (≤ 22.6%) or high percent MD (> 51.9%), and 25(OH)D3 concentrations were compared by multivariable logistic regressions. Multivariable models were adjusted for age, age at menarche, total physical activity and season of blood draw. Median BMI = 27.4 kg/m2, median serum 25(OH)D = 27.3ng/ml. N (high/low): number (high MD/ low MD), OR: odds ratio; 95% CI 95% confidence interval.

Fig 2. Fractional polynomial modelling of the association of serum 25(OH)D3 (ng/ml) with percent mammography density (MD).

A model with 95%CI among women with: A) BMI < median (< 27.4 kgm²), B) BMI ≥ median (≥ 27.4 kgm²).