JAMA. 2004 Feb 11;291(6):711-7.  Related Articles, Links  

Body iron stores in relation to risk of type 2 diabetes in apparently healthy
women.

Jiang R, Manson JE, Meigs JB, Ma J, Rifai N, Hu FB.

Department of Nutrition, Harvard School of Public Health, Boston, MA 02115,
USA. rjiang@hsph.harvard.edu

CONTEXT: Type 2 diabetes is a common manifestation of hemochromatosis, a
disease of iron overload. However, it is not clear whether higher iron stores
predict the development of type 2 diabetes in a healthy population. OBJECTIVE:
To examine plasma ferritin concentration and the ratio of the concentrations of
transferrin receptors to ferritin in relation to risk of type 2 diabetes.
DESIGN, SETTING, AND PARTICIPANTS: Prospective nested case-control study within
the Nurses' Health Study cohort. Of the 32 826 women who provided blood samples
during 1989-1990 and were free of diagnosed diabetes, cardiovascular disease,
and cancer, 698 developed diabetes during 10 years of follow-up. The controls
(n = 716) were matched to cases on age, race, and fasting status; and on body
mass index (BMI) for cases in the top BMI decile. MAIN OUTCOME MEASURE:
Incident cases of type 2 diabetes. RESULTS: Among cases, the mean (SD)
concentration of ferritin was significantly higher (109 [105] vs 71.5 [68.7]
ng/mL for controls; P<.001 for difference) and the mean (SD) ratio of
transferrin receptors to ferritin was significantly lower (102 [205] vs 141
[340], respectively; P =.01). In conditional logistic regression stratified on
the matching factors and controlled for BMI and other diabetes risk factors,
the multivariate relative risks [RRs] of incident type 2 diabetes across
increasing quintiles of ferritin were 1.00, 1.09 (95% confidence interval [CI],
0.70-1.70), 1.26 (95% CI, 0.82-1.95), 1.30 (95% CI, 0.83-2.04), and 2.68 (95%
CI, 1.75-4.11) (P<.001 for trend). The RRs across increasing quintiles of
transferrin receptors to ferritin ratio were 2.44 (95% CI, 1.61-3.71), 1.00
(95% CI, 0.64-1.56), 1.13 (95% CI, 0.73-1.74), 0.99 (95% CI, 0.64-1.53), and
1.00 (P =.01 for trend). Further adjustment for an inflammatory marker
(C-reactive protein) did not change the results appreciably. The associations
persisted within strata defined by levels of BMI, menopausal status, alcohol
consumption, and C-reactive protein. CONCLUSION: Higher iron stores (reflected
by an elevated ferritin concentration and a lower ratio of transferrin
receptors to ferritin) are associated with an increased risk of type 2 diabetes
in healthy women independent of known diabetes risk factors.

PMID: 14871914 [PubMed - in process]

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