Effects of Cardiorespiratory Fitness on Serum Ferritin Concentration and Type 2 Diabetes: The Aerobics Center Longitudinal Studies

Increased Serum Ferritin (SF) concentration could be a contributing factor for developing Type 2 Diabetes (T2D). Physical activity or cardiorespiratory fitness (CRF) also plays an important role in reducing SF concentration and T2D incidence. To determine whether elevated SF concentration is an independent predictor of increased risk of T2D, and increasing CRF reduces SF concentration and decreases risk of T2D, we investigated 5,512 adult participants enrolled in the Aerobics Center Longitudinal Study between 1995 and 2001, and completed initial screening was followed up until November 2007. Incident rates of T2D, and hazard ratios were computed to based on SF quartiles and CRF tertiles. SF concentration was significantly higher in males than females. Participants in highest CRF group had a lower SF concentration than those in lowest CRF group. Male participants in the highest SF quartile level had 1.7 times increased risk for developing T2D as compared to those in the lowest SF quartile group. Incidence rates of new-onset diabetes cases increased significantly across the SF quartiles from SF quartile I to quartile V, but only in males not in females. The study indicates that lower SF concentration was associated with lower risk of T2D in those participating in CRF and suggested that clinicians could use SF concentration as a diabetic predictor in routine medical check-ups and promote regular physical activity or CRF to reduce T2D incidence. The findings encourage healthcare providers to consider SF as a diabetic factor in routine medical checkup and promote regular exercises to reduce T2D incidence.