Relation of risk factors and putative premotor markers for Parkinson's disease.

As both risk and premotor markers are increasingly discussed to play a key role in the pre-diagnostic phase of Parkinson's disease (PD) the aim of this study was to determine the relation between the risk factors hyperechogenicity of the substantia nigra (SN+) and/or positive family history of PD (faPD+) and putative premotor markers for PD. In a cross-sectional analysis of data of the PRIPS cohort, 1,149 volunteers older than 50 years free of PD were included. In addition to the risk factors SN+ and faPD+, olfactory dysfunction was tested using the Sniffin' sticks test and motor examination was performed. History of depression and constipation was evaluated by a semi-structured interview. Of all 1,149 individuals, 880 had none of the risk markers (76.6%), 143 persons (12.4%) had SN+, 84 (7.3%) were classified as faPD+ and 42 (3.7%) persons had both risk factors. Volunteers with SN+ showed olfactory dysfunction and mild motor impairment (p ≤ 0.001) more often. Depression was more prominent in individuals having two risk factors (p = 0.05). An accumulation of premotor markers was seen in the SN+ group with or without concomitant faPD+, but not in persons with faPD+ only. The profile of premotor markers seems to differ in participants having SN+ and/or faPD+, with SN+ showing the overall highest association with most premotor markers, which implies that SN+ might be a strong indicator for a neurodegenerative process.