Late-life hemoglobin and the incidence of Parkinson's disease

Brain iron promotes neurodegeneration in Parkinson's disease (PD). While hemoglobin (Hb) is the most abundant source of peripheral iron in humans, its relationship with PD is uncertain. This report examines the association between Hb in late life and PD incidence. From 1991 to 1993, Hb was measured in 3507 men in the Honolulu-Asia Aging Study. Men were aged 71-93 years and without PD. Participants were followed until 2001 for incident PD. Hb levels declined markedly with age. For men aged 71-75 years, 14.8% had levels < 14 g/dL versus 53.6% in those aged 86 and older (p < 0.001). During follow-up, 47 men developed PD (19.8/10,000 person-years). After age adjustment, PD incidence rose significantly from 10.3 to 34.9/10,000 person-years as Hb increased from < 14 to ≥ 16 g/dL (p = 0.024; relative hazard 3.2; 95% confidence interval, 1.2-8.9). Associations persisted after accounting for early mortality and adjustments for concomitant risk factors. While Hb declines with advancing age, evidence suggests that Hb that remains high in elderly men is associated with an increased risk of PD.