Objective: To characterize subtle behavioral changes observed by Knowledgeable Informants (KIs) of people with Parkinson’s disease (PwPD) before diagnosis.

Background: Earlier identification of PD remains a fundamental challenge in the field. KIs are uniquely positioned to observe changes that may facilitate earlier disease recognition.

Method: We invited KIs to participate in semi-structured interviews in which they described changes they had directly observed in someone close to them before their PD diagnosis. During the review of these interviews, we were struck by subtle behavioral changes observed by multiple KIs as early as decades before diagnosis, prompting a focused examination of these themes. Thematic categories were identified using an inductive qualitative approach in Atlas.ti.

Results: 27 of 63 KIs who participated in qualitative interviews observed pre-diagnostic changes across the following domains [Table 1]:

Driving: Changes spanned motor, visuospatial, executive, and emotional domains, reflecting the integrative demands of driving. Up to 20 years prior to diagnosis, KIs observed heightened highway anxiety and misperception of oncoming vehicles as threatening; persistent lane deviation (up to 15 years prior); and spatial misjudgment and emotional distress during parking (up to 5 years prior) [Table 2].

Other Complex Task Performance: KIs observed difficulty following multi-step instructions (up to 20 years prior) and challenges with visuospatial construction tasks (up to 10 years prior) [Table 3].

Changes in Personality and Sociability: KIs described increased anxiety and reduced adaptability to unexpected situations (up to 19 years prior). Some KIs observed social withdrawal (up to 6 years prior) and diminished conversational engagement (up to 2 years prior), while others described a shift toward monopolizing conversation (up to 1 year prior) [Table 4].

Conclusion: KIs reported observing a broad range of changes up to decades preceding diagnosis, including features less commonly represented in prevailing pre-diagnostic frameworks. Systematic collection of KI histories may complement patient self-report and enhance earlier detection of PD.

Table 1

Table 2

Table 3

Table 4

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MDS Abstracts - https://www.mdsabstracts.org/abstract/subtle-behavioral-changes-observed-by-knowledgeable-informants-up-to-decades-before-parkinsons-disease-diagnosis/