Another limitation of the study include the low participation rate potentially hampering generalizability of results. Participation
rate was higher among subjects below 70 (participation cases: 66%, controls: 39%) and therefore we repeated the analyses on participants age 70 or younger. Results did not materially change (data not shown). In addition, sensitivity analyses were performed leaving out one of the 4 non-neurodegenerative complaints subgroups of controls at a time. This did not materially affect the reported odds ratios (data not shown), suggesting that our results were not influenced by characteristics of one of the neurological conditions included in the control group.