Midbrain hyperechogenicity, hyposmia, mild parkinsonian signs and risk for incident PD over 10 years: A prospective population-based study

Abstract Introduction Associations of substantia nigra (SN) hyperechogenicity on transcranial sonography, olfactory dysfunction, and mild parkinsonian signs (MPS) with incident Parkinson's disease (PD) have only been studied over limited periods of follow-up and their long-term predictive properties are unclear. We aimed to prospectively assess the risk for incident PD over 10 years in community-dwelling elderly individuals with these risk markers. Methods SN-hyperechogenicity, olfactory function and MPS were assessed in the prospective population-based Bruneck Study (2005 assessment; n = 574, aged 55–94 years). Cases of incident PD were identified at 5-year and 10-year follow-up visits. We estimated relative risks of baseline markers for incident cases. Results After excluding 35 cases with PD or secondary parkinsonism at baseline, a total of 20 cases of incident PD were identified from the remaining 539 participants (11 at 5 years and 9 at 10 years). Relative risks for incident PD over the 10-year follow-up period were 7.43 (2.71–20.39), 3.60 (1.48–8.78), and 5.52 (2.43–12.57) for baseline SN-hyperechogenicity, hyposmia, and mild parkinsonian signs, respectively. While risk of hyposmia for incident PD was similar for the two sequential 5-year periods studied, relative risks of SN-hyperechogenicity and MPS were higher for the first five years as compared to later. Conclusion Our findings extend the established risk relationship of SN-hyperechogenicity, hyposmia and MPS with incident PD beyond 5 years.