The Penn Parkinson's Daily Activities Questionnaire-15: Psychometric properties of a brief assessment of cognitive instrumental activities of daily living in Parkinson's disease

•The PDAQ-15 is a brief measure of daily function dependent on cognition.•It was derived from the original 50-item PDAQ.•It correlates highly with measures of global cognitive abilities.•It correlates highly with other existing measures of daily function.•It has good discriminant validity across cognitive stages in Parkinson's disease.