BACKGROUND: Non-motor symptoms (NMS) are common in late stage Parkinson's disease (PD), as the frequency and severity of most of these symptoms increase with advancing disease.

OBJECTIVE: To assess effect of dopaminergic therapy on NMS in late stage PD and to investigate relationships between dopaminergic effect on NMS and on motor function.

METHOD: Thirty PD patients in Hoehn and Yahr (HY) stages IV and V in "on" were included. Dopaminergic effect on non-motor symptomatology was assessed by the modified version of the Non-Motor Symptoms Scale (NMSS) in the "off" and the "on" state during a standardized L-dopa test, in parallel also assessing motor function.

RESULTS: NMS were common and many of the symptoms occurred in >80% of the individuals. The highest NMSS scores were seen within the NMSS domains 3: mood/apathy and 7: urinary in both the "off" and the "on" state. There was a statistically significant (p <  0.001) improvement in the modified NMSS total score (median) from 79 in "off" to 64 in "on". There were statistically significant differences between the "off" and the "on" state for domains 2: sleep/fatigue, 3: mood/apathy, 5: attention/memory, 6: gastrointestinal and 7: urinary. The differences in the NMSS score between the "off" and the "on" state were in general larger for motor responders than for motor non-responders. In motor non-responders, differences of the NMSS score between the "off" and the "on" state were found for the total score, domain 3: mood/apathy and its item 11-flat moods.

CONCLUSION: There is an effect of dopaminergic medication on NMS in late stage PD, to some extent also for those with a non-significant response on motor function during L-dopa test. It is therefore of importance to optimize dopaminergic therapy in order to give the most effective symptomatic treatment possible.