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INTRODUCTION: Persons with dementia experience time-related problems, but there is a lack of instruments evaluating their time processing ability and daily time management. This study aimed to evaluate the psychometric properties of the instruments KaTid®-Senior measuring time processing ability, and Time-S© Senior and Time-Proxy© measuring daily time management for persons with dementia.

METHODS: Persons with dementia (n = 53) and their significant others (n = 49) participated in the study. Rasch analyses were used to evaluate the instruments' rating scale functioning; internal scale validity; person-response validity; unidimensionality; person-separation reliability; and internal consistency. Versions excluding items with poor fit to the Rasch model were also evaluated.

RESULTS: Overall, the Rasch analyses showed acceptable psychometric properties. All instruments met the criteria for unidimensionality and the reliability was good. More challenging items should be added in KaTid-Senior for better targeting of persons with mild dementia. Person-response validity issues in Time-S Senior need to be addressed.

CONCLUSION: The instruments can validly and reliably be used to assess time processing ability and daily time management in persons with dementia in clinical research and healthcare settings. In turn, this can contribute to the development of methods to compensate for impaired time processing ability and daily time management. The assessments can also increase the possibility of early detection of impaired time processing ability and daily time management, thereby facilitating adequate timing of interventions and enhanced occupational performance.