Response shift - The experience of disease progression in Parkinson disease.

OBJECTIVE

To investigate response shift, the recalibration of perceived quality of life (QoL) relative to symptomatic changes in Parkinson disease (PD).

BACKGROUND

Health-related QoL in PD is influenced by improvement vs. decline in disease severity. However, it is unclear how disease course changes internal standards of QoL over time.

METHODS

124 PD patients were subdivided based on Total UPDRS change over 1 year (stable, improved, declined). The EuroQol Visual Analog Scale assessed QoL at baseline (T1) and 1 year later (T2). At T2, patients rated current QoL (T2-current) and reappraised their T1 QoL (T2-retrospective). Recalibration response shifts were represented by the difference between T1 and T2-retrospective QoL ratings.

RESULTS

At follow-up (T2), the total patient sample reported no difference between current (T2 current mean (M) = 76.3) and retrospective (T2-R M = 77.8) QoL ratings. While there was no significant difference between T1 (M = 79.2) and T2-R ratings 1 year later (M = 77.8) for the total sample, there was a change by group interaction (p < 0.005) which showed that retrospectively, decliners reduced ratings (M Δ = -9.0) and improvers increased ratings (M Δ = +6.4) while stable patients did not change.

CONCLUSIONS

When PD patients consider their health status one year ago, decliners recalibrate and downgrade last year's health assessment, while improvers upgrade last year's assessment. Changes in internal calibrations cushion periods of decline or improvement in PD such that patients tend to "stabilize" their general disease course when recalling symptom trajectory, providing insight into the process of adaptation to the effects of disease progression and treatment over time.