Anemia or low hemoglobin levels preceding Parkinson disease

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Abstract
It has been suggested that anemia may be a risk factor for dementia, for restless legs syndrome, and for Parkinson disease (PD). Thus, we investigated the association of anemia with the subsequent risk of PD using a case-control study design. We used the medical records-linkage system of the Rochester Epidemiology Project to identify 196 subjects who developed PD in Olmsted County, Minnesota, from 1976 through 1995. Each incident case was matched by age (+/-1 year) and sex to a general population control. We reviewed the complete medical records of cases and controls in the system to detect anemia defined using the World Health Organization criteria. Anemia was more common in the history of cases than of controls (odds ratio 2.00, 95% confidence interval 1.31-3.06, p = 0.001). The association remained significant after adjustment for cigarette smoking, exposure to pesticides, or hysterectomy (in women). The association was not significantly different between men and women, or between PD patients with or without rest tremor. Analyses stratified by time of onset of anemia showed a greater association for anemia that started 20 to 29 years before the onset of PD. Hemoglobin levels were slightly but consistently lower in cases than in controls across all ages. Our results support an association between anemia experienced early in life and the later development of Parkinson disease. The interpretation of this association remains uncertain.