Sex-specific relationship between serum 25-hydroxyvitamin D concentrations and antinuclear antibodies in U.S. adults, NHANES 2001-2004.

Background: The relationship of serum 25-hydroxyvitamin D concentrations and ANA positivity according to sex stratification is unclear. The propose of this study was to reveal the sex-specific relationship of serum 25-hydroxyvitamin D concentrations and ANA positivity in American people.

Methods: The study was conducted in 2757 subjects from the National Health and Nutrition Examination Survey (NHANES) 2001-2004. The logistic regression models were used to assess the correlation between the risk of ANA positivity and serum 25-hydroxyvitamin D concentrations. Generalized additive models and smooth fitting curves were used to evaluate the non-linear relationship of the risk of ANA positivity and serum 25-hydroxyvitamin D levels.

Results: Following multivariable adjustment, we observed a negative correlation between serum 25-hydroxyvitamin D concentrations and the risk of ANA positivity in male participants, particularly in men non-white individuals and those exposed to second-hand smoke. However, there was no significant relationship observed in the female participants. Additionally, the relationship between serum 25-hydroxyvitamin D concentrations and the risk of ANA positivity followed an L-shaped pattern, with an inflection point at 18 ng/mL. When serum 25-hydroxyvitamin D levels fell below this inflection point, decrease of 1 unit in serum 25-hydroxyvitamin D concentrations was linked to an 8% increase in the adjusted OR of ANA positivity (OR 0.92; 95% CI 0.87, 0.97; p 0.0026).

Conclusions: In American men, nonlinear relationships were observed between serum 25-hydroxyvitamin D concentrations and the risk of ANA positivity.