The on-off effect in Parkinson's disease treated with levodopa with remarks concerning the effect of sleep

The "On-Off Effect" in levodopa treated Parkinson's disease began in a few patients during the first year of treatment. The number of patients suffering from this phenomenon increased rapidly the first three or four years with some continuing increase throughout the six years of the study. Even those whose disease had worsened would become even more incapacitated during parts of each day. One group of patients experienced their initial "On" effect upon arising at their usual hour of awakening. This would last for 1 to 3 hours and was their best time of day.