Drowsy Driving: The Medical Conditions that Could Contribute Driving drowsy is not always just as a result of sleeping badly the night before a trip, being overly fatigued from work, suffering jet lag from your last business trip, or simply being lazy. As many as one out of five people suffer from Excessive Daytime Sleepiness (EDS) and many sleep disturbances and untreated disorders are also linked to drowsy driving. Many medical conditions have sleepiness mentioned in their descriptions, too, and including dementia, narcolepsy, chronic insomnia, restless leg syndrome, and Parkinson's disease...