AimsHigh ferritin and low vitamin D concentrations are associated with an
increased incidence and prevalence of diabetes mellitus but the strength and
nature of the association in older adults remains unclear. We examined the
roles of ferritin and 25-hydroxyvitamin D as independent predictors of
glycaemia in older men.
MethodsCross-sectional analysis of a population-based cohort study of 4,248
community dwelling older men aged 70-89 years in Perth, Western Australia.
Plasma ferritin, 25-hydroxyvitamin D and glucose were assayed. Diabetes was
ascertained from self-report, medication usage and fasting glucose
concentrations. Multivariate analyses adjusted for age, smoking, BMI, waist:hip
ratio, physical activity, hypertension, lipids, creatinine, CRP and medical
comorbidity.
ResultsThere were 588 men with diabetes (13.9%). Ferritin was associated with
fasting glucose in non-diabetic men (0.05 mmol/L per 1SD increase in ferritin,
p=0.01). 25-hydroxyvitamin D was inversely associated with fasting glucose in
non-diabetic men (-0.08 mmol/L per 1SD, p<0.001). Ferritin was not
associated with prevalent diabetes (highest vs. lowest quartile; >225 vs
<65.5 ng/ml: adjusted odds ratio [OR] 0.91, 95% confidence interval [CI],
0.70-1.18, p=0.47). Higher vitamin D was associated with a decreased odds of
prevalent diabetes (highest vs lowest quartile; >81.6nmol/L vs
<52.9nmol/L: adjusted. OR=0.58, 95% CI=0.44-0.75, p<0.001). There was no
interaction between ferritin and vitamin D on diabetes risk. The results were
similar after exclusion of diabetic men using insulin.
ConclusionsIn older men, increased ferritin is associated with increased plasma
fasting glucose concentrations; however it is not a predictor of overall diabetes
risk. Higher 25-hydroxyvitamin D concentrations are independently associated
with lower fasting glucose levels and reduced risk of diabetes. In older adults
manipulation of plasma ferritin may not alter diabetes risk, whereas
interventional studies are required to determine whether vitamin D
supplementation reduce the incidence of diabetes as vitamin D levels are
associated with other health indices.