Differential associations of ferritin and 25-hydroxyvitamin D with fasting glucose and diabetes risk in community dwelling older men

AIMS: We examined associations of ferritin and 25-hydroxyvitamin D with fasting glucose and prevalent diabetes in older men.

METHODS: Cross-sectional analysis of 4,153 community-dwelling men aged 70-89 years in Western Australia. Plasma ferritin, 25-hydroxyvitamin D and glucose were assayed. Diabetes was ascertained from self-report, medications and fasting glucose.

RESULTS: There were 577 men with diabetes (13.9%). In the whole cohort, ferritin was associated with fasting glucose (0.051 mmol/L per 1SD increase in ferritin, p=0.006) and 25-hydroxyvitamin D was inversely associated (-0.085 mmol/L per 1SD, p<0.001). Ferritin was not associated with prevalent diabetes (highest vs. lowest quartile; >225 vs <66 μg/L: adjusted odds ratio [OR] 0.97, 95% confidence interval [CI], 0.74-1.27, p=0.83). Higher vitamin D was associated with decreased odds of prevalent diabetes (highest vs lowest quartile; >82 nmol/L vs <53 nmol/L: OR=0.57, 95% CI=0.43-0.75, p<0.001). There was no interaction between ferritin and vitamin D on diabetes risk.

CONCLUSIONS: In older men, ferritin is associated with fasting glucose but not prevalent diabetes. Higher 25-hydroxyvitamin D concentrations are independently associated with lower fasting glucose and reduced risk of diabetes. Clinical trials are required to determine whether interventions which raise vitamin D concentrations would reduce incidence of diabetes in this expanding demographic group.