title: Vitamin D insufficiency and abnormal hemoglobin a1c in black and white older persons.
abstract: BACKGROUND
  Although vitamin D has been mechanistically linked to insulin secretion and sensitivity, it remains unclear whether low 25-hydroxyvitamin D levels confer an increased risk of impaired glucose metabolism. We evaluated the relationship between vitamin D insufficiency (25-hydroxyvitamin D < 20ng/mL) and abnormal hemoglobin A1c (A1c) (≥6.5%) in community-dwelling older persons and examined whether this relationship differed according to race.
  
  
  METHODS
  Participants were 2,193 persons of age 70-79 years at Year 1 (52% women; 37% black) in the Health, Aging, and Body Composition study who had clinic visits at Years 2 and 4. Logistic regression analyses, adjusted for potential confounders, were used to evaluate the association between vitamin D insufficiency and abnormal A1c 2 years later. Interaction of race and vitamin D insufficiency was tested.
  
  
  RESULTS
  A total of 665 (30%) and 301 (14%) of the participants had vitamin D insufficiency at Year 2 and abnormal A1c at Year 4, respectively. After controlling for demographics, other potential confounders, and diabetes status at Year 4 (n = 477 diabetics), we found that vitamin D insufficiency was associated with an increased likelihood of having abnormal A1c (odds ratio = 1.56; 95% CI: 1.03-2.37). We also found that this relationship persisted among the 1,765 participants without diabetes in Year 2 (odds ratio = 2.33; 95% CI: 1.00-5.40). Findings did not differ by race.
  
  
  CONCLUSIONS
  Vitamin D insufficiency was associated with abnormal A1c levels among black and white older persons independent of diabetes status. Future studies are needed to establish the temporal relationship between vitamin D and A1c in diverse samples of older persons.
authors.affiliation: UCONN Center on Aging, Department of Medicine, University of Connecticut Health Center, Farmington. kositsawat@uchc.edu.
authors.forename: Jatupol
authors.initials: J
authors.lastname: Kositsawat
authors.affiliation: UCONN Center on Aging, Department of Medicine, University of Connecticut Health Center, Farmington.
authors.forename: George A
authors.initials: GA
authors.lastname: Kuchel
authors.affiliation: Department of Biostatistical Sciences, Division of Public Health Sciences and.
authors.forename: Janet A
authors.initials: JA
authors.lastname: Tooze
authors.affiliation: Section on Gerontology & Geriatric Medicine, Sticht Center on Aging, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Denise K
authors.initials: DK
authors.lastname: Houston
authors.affiliation: Department of Epidemiology, Center for Aging and Population Health, Graduate School of Public Health, University of Pittsburgh, Pennsylvania.
authors.forename: Jane A
authors.initials: JA
authors.lastname: Cauley
authors.affiliation: Section on Gerontology & Geriatric Medicine, Sticht Center on Aging, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Kritchevsky
authors.affiliation: Department of Epidemiology, Center for Aging and Population Health, Graduate School of Public Health, University of Pittsburgh, Pennsylvania.
authors.forename: Elsa S
authors.initials: ES
authors.lastname: Strotmeyer
authors.affiliation: Division of General Internal Medicine, University of California, San Francisco.
authors.forename: Alka M
authors.initials: AM
authors.lastname: Kanaya
authors.affiliation: Intramural Research Program, Laboratory of Epidemiology and Population Sciences, National Institute on Aging, Bethesda, Maryland.
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
authors.affiliation: Department of Preventive Medicine, University of Tennessee Health Science Center, Memphis.
authors.forename: Karen C
authors.initials: KC
authors.lastname: Johnson
authors.affiliation: UCONN Center on Aging, Department of Psychiatry, University of Connecticut Health Center, Farmington.
authors.forename: Lisa C
authors.initials: LC
authors.lastname: Barry
mesh_terms: D001741:Black or African American / Q000706:statistics & numerical data*; D000368:Aged; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000150:complications / Q000175:diagnosis / Q000208:ethnology*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D057187:Independent Living; D008137:Longitudinal Studies; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data; D010414:Pennsylvania / Q000453:epidemiology; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013714:Tennessee / Q000453:epidemiology; D014481:United States; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood* / Q000150:complications / Q000175:diagnosis / Q000208:ethnology*; D044465:White People / Q000706:statistics & numerical data*
chemical_list: D015415:Biomarkers; D006442:Glycated Hemoglobin; D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: Hemoglobin A1c; Older persons.; Vitamin D
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