Serum 25OHD concentration as a predictor of haemoglobin A1c among adults living in the USA: NHANES 2003 to 2010
- PMID: 33235955
- PMCID: PMC7664494
- DOI: 10.1136/bmjnph-2019-000029
Serum 25OHD concentration as a predictor of haemoglobin A1c among adults living in the USA: NHANES 2003 to 2010
Abstract
Background: Vitamin D status influences glucose metabolism. Serum 25-hydroxyvitamin D (25OHD) concentrations have been inversely associated with type 2 diabetes risk. The optimal serum 25OHD level needed for adequate glycaemic control is unknown.
Objective: To determine the relationship among serum 25OHD concentrations and degree of glucose regulation using percentage of haemoglobin A1c (HbA1c%).
Methods: Data for adults 20 years from the National Health and Nutrition Examination Survey (NHANES) (2003-2010) were included. A binary logistic regression was used for serum 25OHD (nmol/L) as a continuous variable to determine the OR and 95% CI for HbA1c >6.5%, adjusting for sex, race and body mass index (BMI). Measures of serum 25OHD were grouped into quartiles and entered into a binary logistic regression model to determine the OR and 95% CI for HbA1c >6.5% in an adjusted model.
Results: Across all NHANES cycles, lower serum 25OHD was associated with greater odds of HbA1c 6.5% when adjusting for sex, race, age and BMI (NHANES 2003-2004 (N=4402): OR 0.985, 95% CI 0.979 to 0.990; NHANES 2005-2006 (N=4409): OR 0.976, 95% CI 0.969 to 0.982; NHANES 2007-2008 (N=4525): OR 0.989, 95% CI 0.984 to 0.993; and NHANES 2009-2010 (N=5660): OR 0.988, 95% CI 0.984 to 0.991). In an adjusted model, the lowest quartile of serum 25OHD (0-41 nmol/L, N=4879) was associated with greater odds of HbA1c 6.5% compared with the highest quartile (73-260 nmol/L, N=4472), OR 2.37, 95% CI 2.03 to 2.77. The odds of HbA1c 6.5% were also greater for adults with serum 25OHD considered to be sufficient compared with the highest quartile, OR 1.68, 95% CI 1.56 to 1.61).
Conclusion: Lower serum 25OHD concentrations are associated with poor glycaemic control (HbA1c 6.5%). Sufficient serum 25OHD levels were also associated with poorer blood glucose control. Further research is needed to investigate an optimal serum concentration or threshold to support adequate blood glucose control.
Keywords: hemoglobin a1c; serum 25ohd.
© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.
Conflict of interest statement
Competing interests: None declared.
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