Footnotes

• CFC and MG contributed equally.

• Contributors CFC: data analysis, study design, interpretation of data and drafting manuscript; MG: database management, interpretation of data and study supervision; HU, JG, MK-K, SPi and SPe: interpretation of data, critical revision and drafting manuscript; MdC: study concept, acquisition of data, study supervision and critical revision.

• Funding This is an EU Joint Programme, Neurodegenerative Disease Research (JPND) project. The project is supported through national funding organisations under the aegis of JPND (www.jpnd.eu).

• Competing interests None declared.

• Patient consent for publication Not required.

• Ethics approval The project was approved by the Ethics Commission. All patients and controls signed a written informed consent.

• Provenance and peer review Not commissioned; externally peer reviewed.