Understanding unexpectedly stable trajectories of functional mobility in people with Parkinson’s disease: A mixed methods study

BACKGROUND As Parkinson’s disease (PD) progresses, mobility declines. Reserves (biological, physiological, cognitive, emotional, economical or relational) may help us to understand the phenomenon of unexpectedly stable trajectories of patient-reported functional mobility. OBJECTIVES To investigate reserves moderating the trajectories of patient-reported functional mobility and to understand their daily experience by people with PD. To describe the characteristics of individuals with unexpectedly stable trajectories of functional mobility. METHODS In this explanatory sequential mixed methods study, we combined longitudinal mixed models and qualitative interviews with individuals with unexpectedly stable trajectories of functional mobility. Specifically, we first analysed the reserves moderating the associations between years since diagnosis and patient-reported functional mobility followed by a subsequent collection and analysis of qualitative interviews helping to understand the meaning of these quantitative findings. RESULTS While not significant after correction for multiple testing, functional mobility declined slower in men with 10 to 16 years of education but not in women. By comparing the group with an unexpectedly stable to the group with a decreasing trajectory, the group with an unexpectedly stable trajectory showed, after adjustment for years since diagnosis and multiple testing less patient-reported motor- and non-motor symptoms. The deductive analyses of the semi-structured interviews identified the transport service, i.e., a driving license or the disponibility of someone with a car living in the same household as central facilitating factor of functional mobility. Finally, according to the inductive content analysis psychosocial factors, e.g., self-efficacy, characterised individuals with unexpectedly stable trajectories of functional mobility despite disability (years since diagnosis) and a challenging context (living without a partner or offspring in rural areas). CONCLUSIONS Trajectories of functional mobility in PD seem to be multifactorial in nature, with little evidence for general determinants. Our study highlights the importance of a driving license for functional mobility and supports the provision of local amenities within walking distance to enable active and healthy ageing in place. Psychosocial factors characterised individuals with unexpectedly stable trajectories of functional mobility despite a challenging context. Further research could investigate our generated hypotheses to inform interventions promoting functional mobility.