BACKGROUND: Patient-reported assessments of freezing of gait (FOG) in Parkinson's disease (PD), such as the FOG questionnaire (FOGQ), are needed because FOG is difficult to assess objectively. However, the measurement properties of the FOGQ have been sparsely assessed.

AIM: To assess the measurement properties of the Swedish FOGQ, and to explore relationships between FOGQ scores and other aspects of PD. Methods - Thirty-seven people with PD were assessed with the FOGQ, Unified PD Rating Scale (UPDRS), Hoehn and Yahr (HY), Falls-Efficacy Scale [FES(S)], timed gait tests, and the SF-36 physical functioning (PF) scale.

RESULTS: Mean (SD) FOGQ item scores ranged between 1.3 and 2.1 (1.2-1.5); corrected item-total correlations ranged between 0.80 and 0.94. Reliability was 0.95. Mean (SD) and median (q1-q3) FOGQ scores were 9.6 (7.4) and 10 (2-15). Floor and ceiling effects were < or =5.4%. FOGQ correlated strongest with UPDRS part II (ADL), UPDRS item 14 (freezing), and HY (r(S) 0.65-0.66). FOGQ scores correlated with PD duration, the Timed Up and Go test, dyskinesia, motor fluctuations, FES(S), and PF scores (r(S) 0.40-0.62). Fallers had higher FOGQ scores than non-fallers (median 12.5 vs 5.0).

CONCLUSION: Data support the measurement properties of the Swedish FOGQ by replicating and extending previous psychometric reports.